阅读说明：本技术 具有可重新定位电极的除霜设备 (Defrost apparatus with repositionable electrodes ) 是由 大卫·保罗·莱斯特 利昂内尔·蒙然 于 2019-11-27 设计创作，主要内容包括：一种除霜系统包括：射频(RF)信号源；至少一个电极,至少一个电极靠近其内定位有待除霜负载的腔；传输路径,传输路径在RF信号源与电极之间；在传输路径中的至少一个母排,至少一个母排包括电极可以耦合到的多个端口；可重新定位搁架,可重新定位搁架附接到电极；以及安置在腔的侧壁上的多个支撑结构,多个支撑结构支撑可重新定位搁架。支座隔离器可以将电极附接到可重新定位搁架并且可以将电极与可重新定位搁架电隔离。通过移动可重新定位搁架以由多个支撑结构中的不同支撑结构支撑,同时将电极耦合到母排的多个端口中的不同端口,可以改变电极的竖直位置。(A defrost system comprising: a Radio Frequency (RF) signal source; at least one electrode proximate to a cavity within which a load to be defrosted is positioned; a transmission path between the RF signal source and the electrode; at least one busbar in the transmission path, the at least one busbar comprising a plurality of ports to which electrodes may be coupled; a repositionable shelf attached to the electrode; and a plurality of support structures disposed on the sidewalls of the cavity, the plurality of support structures supporting the repositionable shelf. The standoff isolator can attach the electrode to the repositionable shelf and can electrically isolate the electrode from the repositionable shelf. The vertical position of the electrode may be changed by moving the repositionable shelf to be supported by a different one of the plurality of support structures while coupling the electrode to a different one of the plurality of ports of the busbar.)

1. A heat augmentation system having a cavity for receiving a load, the heat augmentation system comprising:

a first repositionable electrode disposed in the cavity;

a first busbar disposed in the cavity, the first repositionable electrode being physically and electrically connectable to the first busbar;

a second repositionable electrode disposed in the cavity;

a second busbar disposed in the cavity, the second repositionable electrode being physically and electrically connectable to the second busbar;

a plurality of shelf support structures disposed within the cavity, wherein the plurality of shelf support structures are configured to support the first and second repositionable electrodes at a plurality of heights within the cavity; and

a radio frequency signal source electrically connected to one or both of the first and second repositionable electrodes via the first and second bus bars, respectively, the radio frequency signal source configured to provide radio frequency energy to one or both of the first and second repositionable electrodes.

2. The heat augmentation system of claim 1, wherein the first busbar comprises a first plurality of ports, the second busbar comprises a second plurality of ports, the first repositionable electrode is inserted into one of the first plurality of ports and the second repositionable electrode is inserted into one of the second plurality of ports.

3. The heat augmentation system of claim 1, further comprising:

a variable impedance matching network coupled between the source of radio frequency signals and one or both of the first and second repositionable electrodes and having a variable impedance, wherein the variable impedance matching network is configured to adjust the variable impedance based on one or more parameters of radio frequency energy selected from the group consisting of reflected power, both forward and reflected power, and S11 parameters.

4. The heat augmentation system of claim 1, further comprising:

a first repositionable shelf attached to the first repositionable electrode; and

a second repositionable shelf attached to the second repositionable electrode, wherein the first and second repositionable shelves are supported by the plurality of shelf support structures.

5. The heat augmentation system of claim 4, further comprising:

a first plurality of standoff isolators attaching the first repositionable shelf to the first repositionable electrode and providing separation between the first repositionable shelf and the first repositionable electrode to electrically isolate the first repositionable shelf from the first repositionable electrode; and

a second plurality of standoff isolators attaching the second repositionable shelf to the second repositionable electrode and providing separation between the second repositionable shelf and the second repositionable electrode to electrically isolate the second repositionable shelf from the second repositionable electrode.

6. The heat augmentation system of claim 5, wherein a standoff isolator of the first plurality of standoff isolators comprises:

a cylindrical portion at a first end of the standoff isolator;

a threaded portion at a second end of the standoff isolator opposite the first end, the threaded portion inserted through a hole in the first repositionable electrode; and

a threaded cap that is threaded onto the threaded portion to secure the standoff separator to the first repositionable electrode.

7. The heat augmentation system of claim 6, wherein the cylindrical portion of the standoff isolator comprises a through-hole, and the first repositionable shelf comprises a rod extending through the through-hole attaching the standoff isolator to the first repositionable shelf.

8. The thermal augmentation system of claim 1, wherein the radio frequency signal source is further configured to provide a first balanced radio frequency signal to the first repositionable electrode via the first bus bar, and a second balanced radio frequency signal to the second repositionable electrode via the second bus bar.

9. A system, comprising:

a containment structure forming a cavity;

a first busbar disposed in the cavity, the first busbar including a first plurality of ports at different heights from a bottom of the cavity;

a first repositionable electrode disposed in the cavity at a first selectable height, one of the first plurality of ports receiving a first connector portion of the first repositionable electrode to electrically connect the first repositionable electrode to a first port of the first plurality of ports of the first busbar;

a second repositionable electrode disposed in the cavity at a second selectable height different from the first selectable height such that the first repositionable electrode and the second repositionable electrode are parallel to each other; and

a radio frequency signal source that supplies radio frequency energy to one or both of the first or second repositionable electrodes.

10. A heat augmentation system, comprising:

a containment structure forming a cavity;

a support structure disposed on an inner wall of the cavity;

a first repositionable shelf supportable by a first set of the support structure;

an upper electrode attached to the first repositionable shelf;

a second repositionable shelf supportable by a second leg of the support structure;

a lower electrode attached to the second repositionable shelf; and

a radio frequency signal source electrically connected to one or both of the upper electrode and the lower electrode, the radio frequency signal source configured to provide radio frequency energy to one or both of the upper electrode and the lower electrode.

Technical Field

Embodiments of the subject matter described herein relate generally to apparatus and methods for defrosting a load using Radio Frequency (RF) energy.

Background

Conventional capacitive food defrosting (or thawing) systems include large planar electrodes housed within a heated compartment. After placing the food load between the electrodes and contacting the electrodes with the food load, low power electromagnetic energy is supplied to the electrodes to provide a controlled warming of the food load. When the food load thaws during defrost, the impedance of the food load changes. Thus, during defrost operations, the power delivered to the food load also changes. The duration of the defrost operation may be determined, for example, based on the weight of the food load, and a timer may be used to control the cessation of operation.

While good defrost results can be obtained using such a system, variations in the size of the food load can result in inefficient defrosting of the food load. What is needed is an apparatus and method for defrosting a food load (or other type of load) that can defrost the entire load efficiently and evenly.

Disclosure of Invention

According to a first aspect of the present invention there is provided a heat augmentation system having a cavity for receiving a load, the heat augmentation system comprising:

a first repositionable electrode disposed in the cavity;

a first busbar disposed in the cavity, the first repositionable electrode being physically and electrically connectable to the first busbar;

a second repositionable electrode disposed in the cavity;

a second busbar disposed in the cavity, the second repositionable electrode being physically and electrically connectable to the second busbar;

a plurality of shelf support structures disposed within the cavity, wherein the plurality of shelf support structures are configured to support the first and second repositionable electrodes at a plurality of heights within the cavity; and

a radio frequency signal source electrically connected to one or both of the first and second repositionable electrodes via the first and second bus bars, respectively, the radio frequency signal source configured to provide radio frequency energy to one or both of the first and second repositionable electrodes.

In one or more embodiments, the first busbar comprises a first plurality of ports, the second busbar comprises a second plurality of ports, the first repositionable electrode is inserted into one of the first plurality of ports and the second repositionable electrode is inserted into one of the second plurality of ports.

In one or more embodiments, the heat addition system further comprises:

a variable impedance matching network coupled between the source of radio frequency signals and one or both of the first and second repositionable electrodes and having a variable impedance, wherein the variable impedance matching network is configured to adjust the variable impedance based on one or more parameters of radio frequency energy selected from the group consisting of reflected power, both forward and reflected power, and S11 parameters.

In one or more embodiments, the heat addition system further comprises:

a first repositionable shelf attached to the first repositionable electrode; and

a second repositionable shelf attached to the second repositionable electrode, wherein the first and second repositionable shelves are supported by the plurality of shelf support structures.

In one or more embodiments, the heat addition system further comprises:

a first plurality of standoff isolators attaching the first repositionable shelf to the first repositionable electrode and providing separation between the first repositionable shelf and the first repositionable electrode to electrically isolate the first repositionable shelf from the first repositionable electrode; and

a second plurality of standoff isolators attaching the second repositionable shelf to the second repositionable electrode and providing separation between the second repositionable shelf and the second repositionable electrode to electrically isolate the second repositionable shelf from the second repositionable electrode.

In one or more embodiments, a standoff isolator of the first plurality of standoff isolators comprises:

a cylindrical portion at a first end of the standoff isolator;

a threaded portion at a second end of the standoff isolator opposite the first end, the threaded portion inserted through a hole in the first repositionable electrode; and

a threaded cap that is threaded onto the threaded portion to secure the standoff separator to the first repositionable electrode.

In one or more embodiments, the cylindrical portion of the standoff isolator includes a through-hole, and the first repositionable shelf includes a rod extending through the through-hole attaching the standoff isolator to the first repositionable shelf.

In one or more embodiments, the rf signal source is further configured to provide a first balanced rf signal to the first repositionable electrode via the first bus bar and a second balanced rf signal to the second repositionable electrode via the second bus bar.

In one or more embodiments, the second repositionable electrode is electrically connectable to a ground terminal through the second bus bar.

According to a second aspect of the invention, there is provided a system comprising:

a containment structure forming a cavity;

a first busbar disposed in the cavity, the first busbar including a first plurality of ports at different heights from a bottom of the cavity;

a first repositionable electrode disposed in the cavity at a first selectable height, one of the first plurality of ports receiving a first connector portion of the first repositionable electrode to electrically connect the first repositionable electrode to a first port of the first plurality of ports of the first busbar;

a second repositionable electrode disposed in the cavity at a second selectable height different from the first selectable height such that the first repositionable electrode and the second repositionable electrode are parallel to each other; and

a radio frequency signal source that supplies radio frequency energy to one or both of the first or second repositionable electrodes.

In one or more embodiments, the system further comprises:

a second busbar disposed in the cavity, the second busbar including a second plurality of ports, one of the second plurality of ports receiving a second connector portion of the second repositionable electrode to electrically connect the second repositionable electrode to a second port of the second plurality of ports of the second busbar.

In one or more embodiments, the second repositionable electrode is electrically connectable to ground through the second bus bar.

In one or more embodiments, the system further comprises:

a plurality of support structures disposed at different heights on an inner wall of the cavity;

a first repositionable shelf supportable by a first set of the plurality of support structures;

a second repositionable shelf supportable by a second leg of the plurality of support structures;

a first plurality of dielectric standoff isolators attaching the first repositionable shelf to the first repositionable electrode and providing separation between the first repositionable shelf and the first repositionable electrode; and

a second plurality of dielectric standoff isolators attaching the second repositionable shelf to the second repositionable electrode and providing separation between the second repositionable shelf and the second repositionable electrode.

In one or more embodiments, a dielectric support isolator of the first plurality of dielectric support isolators comprises:

a cylindrical portion at a first end of the dielectric standoff isolator;

a threaded portion at a second end of the dielectric standoff isolator opposite the first end, the threaded portion inserted through a hole in the first repositionable electrode; and

a threaded cap screwed onto the threaded portion to secure the dielectric standoff separator to the first repositionable electrode.

In one or more embodiments, the rf signal source is electrically connected to the second busbar and supplies rf energy to the second repositionable electrode through the second busbar.

In one or more embodiments, the system further comprises:

a variable impedance matching network coupled between the radio frequency signal source and one or both of the first and second repositionable electrodes and having a variable impedance, wherein the variable impedance matching network is configured to adjust the variable impedance based on one or more parameters of the radio frequency signal selected from the group consisting of reflected power, both forward and reflected power, and S11 parameters.

According to a third aspect of the present invention, there is provided a heat adding system comprising:

a containment structure forming a cavity;

a support structure disposed on an inner wall of the cavity;

a first repositionable shelf supportable by a first set of the support structure;

an upper electrode attached to the first repositionable shelf;

a second repositionable shelf supportable by a second leg of the support structure;

a lower electrode attached to the second repositionable shelf; and

a radio frequency signal source electrically connected to one or both of the upper electrode and the lower electrode, the radio frequency signal source configured to provide radio frequency energy to one or both of the upper electrode and the lower electrode.

In one or more embodiments, the heat addition system further comprises:

a first plurality of standoff spacers attaching the first repositionable shelf to the upper electrode and separating the first repositionable shelf from the upper electrode; and

a second plurality of standoff spacers attaching the second repositionable shelf to the lower electrode and separating the second repositionable shelf from the second electrode.

In one or more embodiments, the first plurality of standoff isolators comprises a dielectric material and electrically insulates the first repositionable shelf from the upper electrode.

In one or more embodiments, the heat addition system further comprises:

a first busbar disposed on a wall of the containment structure, the first busbar including a first plurality of ports, one of the ports receiving a first connector portion of the upper electrode to electrically connect the upper electrode to the first busbar; and

a second busbar disposed on the wall of the containment structure, the second busbar including a second plurality of ports, one of the second plurality of ports receiving a second connector portion of the lower electrode to electrically connect the lower electrode to the second busbar.

These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.

Drawings

A more complete understanding of the present subject matter may be derived by referring to the detailed description and claims when considered in conjunction with the following figures, wherein like reference numbers refer to similar elements throughout the figures.

Fig. 1 is a perspective view of a defrosting appliance according to an example embodiment.

Fig. 2 is a perspective view of a refrigerator/freezer appliance including other example embodiments of the defrost system.

Fig. 3 is a simplified block diagram of an unbalanced defrost device according to an example embodiment.

Fig. 4 is a simplified block diagram of a balanced defrost device according to another example embodiment.

FIG. 5 is a perspective view of a defrost system having a repositionable electrode according to an example embodiment.

FIG. 6 is a perspective view of a modified version of the defrost system of FIG. 5 in which standoff separators are coupled to each of two repositionable electrodes, according to an example embodiment.

FIG. 7 is a close-up perspective view of one of the standoff separators of the defrost system of FIG. 6 according to an example embodiment.

FIG. 8 is an isolated view of an illustrative standoff isolator in accordance with an example embodiment.

Fig. 9 is a top down view of the defrost system of fig. 6 in a single ended configuration according to an example embodiment.

Fig. 10 is a top down view of the defrost system of fig. 6 in a double ended configuration according to another example embodiment.

FIG. 11 is a flow chart of a method of operating a defrost system in which the defrost system includes a source of self-oscillating signals, according to an example embodiment.

Detailed Description

The following detailed description is merely illustrative in nature and is not intended to limit the embodiments of the subject matter or the application and uses of such embodiments. As used herein, "exemplary" and "example" mean "serving as an example, instance, or illustration. Any embodiment described herein as illustrative or exemplary is not necessarily to be construed as preferred or advantageous over other embodiments. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, or the following detailed description.

Embodiments of the subject matter described herein relate to a solid state defrost device that may be incorporated into a stand-alone appliance or other system. As described in more detail below, embodiments of the solid state defrost device include both "unbalanced" defrost devices and "balanced" devices. For example, an exemplary "unbalanced" defrost system is implemented using a first electrode disposed in a cavity. In contrast, an exemplary "balanced" defrost system is implemented using first and second electrodes disposed in a cavity.

Generally, the term "defrost" means to increase the temperature of a frozen load (e.g., a food load or other type of load) to a temperature at which the load is no longer frozen (e.g., a temperature at or near 0 degrees celsius). As used herein, the term "defrost" refers more broadly to a process in which the thermal energy or temperature of a load (e.g., a food load or other type of load) is increased by providing RF power to the load. Thus, in various embodiments, a "defrost operation" may be performed on a load at any initial temperature (e.g., any initial temperature above or below 0 degrees celsius), and the defrost operation may be stopped at any final temperature above the initial temperature (e.g., including a final temperature above or below 0 degrees celsius). That is, the "defrost operation" and "defrost system" described herein may alternatively be referred to as a "heat increment operation" and a "heat increment system". The term "defrost" should not be construed to limit the application of the present invention to methods or systems that can only raise the temperature of a frozen load to a temperature at or near 0 degrees celsius.

Conventional heating systems (e.g., microwave ovens, conventional ovens, etc.) are generally not suitable for integrating RF defrost systems to achieve a quick defrost function of frozen food products or other suitable loads. This is because the load-holding cavity of such conventional systems typically has a relatively large internal height between the floor and ceiling of the cavity (e.g., 20-30cm for microwave ovens and 50-80cm for conventional ovens). If the electric field generated during the RF defrost operation needs to extend across such a distance, then the defrost efficiency, which may be defined as the amount of energy input to the defrost chamber compared to the amount of energy absorbed by the load, will typically be low or in some cases impossible. Thus, to concentrate an electric field according to various embodiments, a pair of conductive (e.g., metallic or partially metallic) plates may be inserted into the cavity. The presence of these conductive plates, sometimes referred to herein as "repositionable electrodes," can concentrate the electric field generated by the application of RF energy to one of the electrodes in the space between the two electrodes. Additionally, one or both of the electrodes may be connected to one or more busbars located on one or more walls of the cavity when inserted into the cavity. For example, one of the electrodes may be electrically connected to a first output of the RF subsystem (e.g., to receive an unbalanced RF signal or to receive a first balanced RF signal) by a first busbar. In embodiments with two electrodes, the other electrode may be connected to a second output of the RF subsystem (e.g., to receive a second balanced RF signal) or to a common or ground voltage through a second busbar. In the above example, both electrodes may be repositionable. However, in other embodiments, one electrode may be in a fixed position while the other electrode may be repositionable. By providing one or more repositionable electrodes, the defrost system can be adapted to accommodate loads of different sizes, allowing increased flexibility and/or placement of loads in different areas of the system without reducing RF defrost efficiency due to reduced electric field.

Fig. 1 is a perspective view of a defrost system 100 according to an example embodiment. The defrost system 100 includes a defrost chamber 110 (e.g., chamber 360 of fig. 3, chamber 460 of fig. 4, chamber 560 of fig. 5), a control panel 120, one or more Radio Frequency (RF) signal sources (e.g., RF signal source 320 of fig. 3, RF signal source 420 of fig. 4), a power source (e.g., power source 326 of fig. 3, power source 426 of fig. 4), a first repositionable electrode 170 (e.g., first repositionable electrode 340 of fig. 3, first repositionable electrode 440 of fig. 4, first repositionable electrode 540 of fig. 5), a repositionable shelf 123 including a first repositionable electrode 170, a second repositionable electrode 172 (e.g., second repositionable electrode 472 of fig. 4, second repositionable electrode 550 of fig. 5), a repositionable shelf 124 including a second repositionable electrode 172, a system controller (e.g., system controller 312, of fig. 3, System controller 412 of fig. 4), and support structure 122. In some embodiments, the first repositionable electrode 170 and the second repositionable electrode 172 can be conductive (e.g., metallic) materials embedded in the repositionable shelves 123 and 124, respectively. In other embodiments, the repositionable shelves 123 and 124 can each be completely electrically conductive, such that the entire repositionable shelf 123 constitutes the first repositionable electrode 170 and the entire repositionable shelf 124 constitutes the second repositionable electrode 172. In some embodiments, the repositionable shelves 123 and 124 can be wire frames that support the repositionable electrodes 170 and 172, respectively, and are electrically isolated from the repositionable electrodes 170 and 172, respectively, by standoff isolators (e.g., standoff isolators 530 of fig. 6, 7).

The defrost chamber 110 is defined by the inner surfaces of the top chamber wall 111, the bottom chamber wall 112, the side chamber walls 113, 114, and the rear chamber wall 115, and the inner surface of the door 116. With the door 116 closed, the defrost chamber 110 defines an enclosed air chamber. As used herein, the term "air chamber" may mean an enclosed area or volume that contains air or other gas (e.g., defrost chamber 110). The repositionable shelves 123 and 124 may be supported by pairs of opposing support structures 122. For example, the support structure 122 may be a rail attached to the walls 113 and 114 or may be a recessed portion of the walls 113 and 114.

According to an "unbalanced" embodiment, the first repositionable electrode 170 is electrically coupled to an RF signal source from which an RF signal is received via a bus bar 128 (e.g., bus bar 502 of fig. 5) disposed on the rear cavity wall 115, while the second repositionable electrode 172 is electrically coupled to ground via a bus bar 126 (e.g., bus bar 504 of fig. 5) disposed on the rear cavity wall 115. In an alternative embodiment, the second repositionable electrode 172 may be electrically coupled to ground via contact with the support structure 122. In this configuration, the system can be simply modeled as a capacitor, with the first repositionable electrode 170 serving as one conductive plate (or electrode), the second repositionable electrode 172 serving as a second conductive plate (or electrode), and the air cavity between the electrodes 170 and 172 (including any load contained therein) serving as the dielectric between the first and second conductive plates. Although not shown in fig. 1, a non-conductive barrier (e.g., barrier 362 of fig. 3, barrier 462 of fig. 4) may also be included in the system 100, and the non-conductive barrier may function to electrically and physically isolate (e.g., separate) the load from the second repositionable electrode 172. In another alternative embodiment, the second repositionable electrode may be omitted, and some or all of the cavity walls 111, 112, 113, 114, 115 may be grounded, with the top wall 111 or the bottom wall 112 acting as a second grounded electrode.

According to a "balanced" embodiment, the first repositionable electrode 170 is electrically coupled to a source of RF signals from which a first RF signal is received via the busbar 128 (e.g., busbar 502 of fig. 5), while the second repositionable electrode 172 is electrically coupled to a source of RF signals from which a second RF signal is received via the busbar 126 (e.g., busbar 504 of fig. 5), where the first and second RF signals are balanced RF signals. In this configuration, the system can also be simply modeled as a capacitor, with the first repositionable electrode 170 serving as one conductive plate (or electrode), the second repositionable electrode 172 serving as a second conductive plate (or electrode), and the air cavity between the electrode 170 and the electrode 172 (including any load contained therein) serving as a dielectric between the first and second conductive plates. Although not shown in fig. 1, a non-conductive barrier (e.g., barrier 462 of fig. 4) may also be included in the system 100, and the non-conductive barrier may function to electrically and physically isolate (e.g., separate) the load from the second repositionable electrode 172.

According to an embodiment, during operation of the defrost system 100, a user (not shown) may place the repositionable shelf 124 in a first selected position within the defrost chamber 110 and may place the repositionable shelf 123 in a second selected position within the defrost chamber 110 (e.g., above the repositionable shelf 124) such that the repositionable shelves 123 and 124 are supported by respective different pairs of support structures 122. For example, when a user intends to heat a small load (e.g., a load having a relatively small height), the repositionable shelves 123 and 124 may be positioned closer together than when a user intends to heat a larger load (e.g., a load having a relatively large height). Generally, the user can selectively place the repositionable shelves 123 and 124 in a position within the defrost chamber 110 that provides a minimum distance between the repositionable shelf 124 and the repositionable shelf 123 while still providing sufficient space to accommodate a load that the user intends to place on the repositionable shelf 124. Once the repositionable shelves 123 and 124 are secured in the cavity 110, a user can place one or more loads (e.g., food and/or liquid) into the defrost cavity 110 (e.g., between the repositionable shelf 124 and the repositionable shelf 123) and optionally can provide input via the control panel 120 specifying characteristics of the one or more loads. For example, the specified characteristic may include an approximate weight of the load. Further, the specified load characteristic may be indicative of one or more materials (e.g., meat, bread, liquid) forming the load. In alternative embodiments, the load characteristics may be obtained in some other manner, such as by scanning a bar code on the load package or receiving a Radio Frequency Identification (RFID) signal from an RFID tag on or embedded within the load. Either way, as will be described in more detail below, information regarding such load characteristics may enable the system controller to control the RF heating process.

To initiate the defrost operation, the user may provide input via the control panel 120. In response, the system controller causes one or more RF signal sources (e.g., RF signal source 320 of fig. 3, RF signal source 420 of fig. 4) to supply an RF signal to either the first repositionable electrode 170 or the second repositionable electrode 172 in an unbalanced embodiment, or to both the first repositionable electrode 170 and the second repositionable electrode 172 in a balanced embodiment, and the one or more electrodes responsively radiate electromagnetic energy into the defrost chamber 110. The electromagnetic energy increases the thermal energy of the load (i.e., the electromagnetic energy warms the load).

During defrost operations, the impedance of the load (and thus the total input impedance of the chamber 110 plus the load) changes as the thermal energy of the load increases. The impedance change changes the RF energy absorbed into the load and thus changes the magnitude of the reflected power. According to an embodiment, power detection circuitry (e.g., RF detection circuitry, not shown) continuously or periodically measures reflected power (e.g., magnitude and optionally phase of reflected power) in a transmission path (e.g., transmission path 328 of fig. 3, transmission path 428/430 of fig. 4) between an RF signal source (e.g., RF signal source 320 of fig. 3, RF signal source 420 of fig. 4) and one or more electrodes 170, 172, and in some embodiments also measures forward power (e.g., magnitude and optionally phase of forward power). Based on these measurements, a system controller (e.g., system controller 312 of fig. 3, system controller 412 of fig. 4) may detect completion of the defrost operation. According to another embodiment, a variable impedance matching network (e.g., network 370 of fig. 3, network 470 of fig. 4) is disposed along the transmission path of the RF signal and based on the reflected power measurement (or both the forward power measurement and the reflected power measurement), the system controller may change the state of the impedance matching network during the defrost operation to increase absorption of the RF power by the load (e.g., to decrease the reflected power).

The defrost system 100 of fig. 1 is implemented as a reverse-top appliance. Alternatively, the components of the defrost system may be incorporated into other types of systems or appliances. For example, fig. 2 is a perspective view of a refrigerator/freezer appliance 200 that includes other example embodiments of defrost systems 210, 220. More specifically, the defrost system 210 is shown incorporated into the freezer compartment 212 of the system 200, and the defrost system 220 is shown incorporated into the refrigerator compartment 222 of the system. An actual refrigerator/freezer appliance would likely include only one of the defrost systems 210, 220, but both are shown in fig. 2 to convey both embodiments in brevity.

Similar to defrost system 100, each of defrost systems 210, 220 includes a defrost chamber, control panels 214 and 224, one or more RF signal sources (e.g., RF signal source 320 of fig. 3, RF signal source 420 of fig. 4), a power source (e.g., power source 326 of fig. 3, power source 426 of fig. 4), a first repositionable electrode (e.g., electrode 170 of fig. 1, electrode 340 of fig. 3, electrode 440 of fig. 4, electrode 540 of fig. 5), a plurality of support structures (e.g., support structure 122 of fig. 1, support structure 322 of fig. 3, support structure 422 of fig. 4, support structures 516, 518 of fig. 5) disposed on opposing interior walls of the defrost chamber, a first repositionable shelf (e.g., repositionable shelf 123 of fig. 1) supported by one pair of the support structures and including the first repositionable electrode, a second repositionable shelf (e.g., the repositionable shelf 124 of fig. 1), and a system controller (e.g., the system controller 312 of fig. 3, the system controller 412 of fig. 4). For example, where the support structure rests on a side wall of the containment structure, the defrost cavity can be defined by the inner surfaces of the bottom, side, front, and rear walls of the containment structure (e.g., containment structure 366 of fig. 3, containment structure 466 of fig. 4, containment structure 566 of fig. 5). The front wall of the containment structure may be a door or other structure that can be opened and closed, which when closed, creates an enclosed air chamber. In various embodiments, the components and functions of the defrost systems 210, 220 may be substantially the same as the components and functions of the defrost system 100.

Further, according to embodiments, each of the defrost systems 210, 220 may be in sufficient thermal communication with a freezer compartment 212 or a refrigerator compartment 222, respectively, with the system 210 disposed in the freezer compartment 212 and the system 220 disposed in the refrigerator compartment 222. In such an embodiment, after the defrost operation is complete, the load may be maintained at a safe temperature (i.e., a temperature that prevents food spoilage) until the load is removed from the system 210, 220. More specifically, upon completion of a defrost operation by the freezer-based defrost system 210, the cavity containing the defrost load may be in thermal communication with the freezer appliance 212, and the load may be refreezed if it is not removed from the cavity in time. Similarly, upon completion of the defrost operation by the refrigerator-based defrost system 220, the cavity containing the defrost load may be in thermal communication with the refrigerator compartment 222, and if the load is not removed from the cavity in time, the load may be maintained in a defrost state at the temperature within the refrigerator compartment 222.

Based on the description herein, one of ordinary skill in the art will appreciate that embodiments of the defrost system may also be incorporated into systems or appliances having other configurations. Thus, the above-described embodiments of the defrost systems in the stand-alone appliances, the freezer and the refrigerator are not meant to limit the use of the embodiments to only those types of systems.

Although the defrost systems 100, 200 are shown with their components in a relative orientation, particularly with respect to each other, it should be understood that the various components may be oriented differently. Further, the physical configuration of the various components may differ. For example, the control panels 120, 214, 224 may have more, fewer, or different user interface elements, and/or the user interface elements may be arranged differently. Further, while a substantially cuboidal defrost chamber 110 is shown in fig. 1, it should be understood that in other embodiments, the defrost chamber may have a different shape (e.g., cylindrical, etc.). Additionally, the defrost system 100, 210, 220 may include additional components (e.g., fans, fixed or rotating plates, trays, cords, etc.) not specifically depicted in fig. 1, 2.

Fig. 3 is a simplified block diagram of an unbalanced defrost system 300 (e.g., defrost system 100 of fig. 1, defrost systems 210, 220 of fig. 2) according to an example embodiment. In one embodiment, the defrost system 300 includes an RF subsystem 310, a defrost chamber 360, a user interface 380, a system controller 312, an RF signal source 320, power and bias circuitry 326, a first repositionable electrode 340 (e.g., repositionable electrode 170 of fig. 1), a support structure 322 (e.g., support structure 122 of fig. 1, support structures 516, 518 of fig. 5), a repositionable shelf 323 (e.g., repositionable shelf 123 of fig. 1) supported by one pair of support structures 322 and including the first repositionable electrode 340, a second repositionable electrode 372 (e.g., repositionable electrode 172 of fig. 1), a repositionable shelf 324 (e.g., repositionable shelf 124 of fig. 1) supported by another pair of support structures 322 and including the second electrode 372, a non-conductive barrier 362, or the like disposed over the repositionable shelf 324, And a receiving structure 366. In some embodiments, the first repositionable electrode 340 and the second repositionable electrode 372 may be (e.g., in or on) a conductive material embedded or disposed on the repositionable shelves 323 and 324, respectively. In other embodiments, the repositionable shelves 323 and 324 can be a fully conductive material, such that all of the repositionable shelves 323 function as the first repositionable electrode 340 and all of the repositionable shelves 324 function as the second repositionable electrode 372. In some embodiments, the repositionable shelves 323 and 324 may be wire frames that support the repositionable electrodes 340 and 372, respectively, and are electrically isolated from the repositionable electrodes 340 and 372, respectively, by standoff isolators (e.g., standoff isolators 530 of fig. 6, 7). It should be understood that fig. 3 is a simplified representation of the defrost system 300 for purposes of explanation and ease of description, and that practical embodiments may include other devices and components to provide additional functionality and features, and/or that the defrost system 300 may be part of a larger electrical system.

The user interface 380 may correspond to a control panel (e.g., the control panel 120 of fig. 1, the control panels 214, 224 of fig. 2), for example, that enables a user to provide input to the defrost system 300 regarding parameters of the defrost operation (e.g., characteristics of the load to be defrosted, etc.), the activate and deactivate buttons, mechanical controls (e.g., door/drawer unlatch), and so forth. Further, the user interface may be configured to provide user perceptible outputs (e.g., a countdown timer, a visual indicia indicating the progress or completion of the defrost operation, and/or an audible tone indicating the completion of the defrost operation) and other information indicating the status of the defrost operation.

Some embodiments of the defrost system 300 may include one or more temperature sensors, one or more Infrared (IR) sensors, and/or one or more weight sensors 390, although some or all of these sensor components may not be included. One or more temperature sensors and/or one or more IR sensors may be positioned at locations that enable the temperature of load 364 to be sensed during defrost operations. When provided to the system controller 312, the temperature information may enable the system controller 312 to vary the power of the RF signal supplied by the RF signal source 320 (e.g., by controlling the bias and/or supply voltage provided by the power and bias circuitry 326) and/or determine when the defrost operation should be terminated. One or more weight sensors may be positioned under load 364 and configured to provide an estimate of the weight of load 364 to system controller 312. The system controller 312 may use this information, for example, to determine a desired power level of the RF signal supplied by the RF signal source 320 and/or to determine an approximate duration of the defrost operation.

In one embodiment, RF subsystem 310 includes a system controller 312, an RF signal source 320, a variable impedance matching network 370, and power and bias circuitry 326. The system controller 312 may include one or more general-purpose or special-purpose processors (e.g., microprocessors, microcontrollers, Application Specific Integrated Circuits (ASICs), etc.), volatile and/or non-volatile memory (e.g., Random Access Memory (RAM), Read Only Memory (ROM), flash memory, various registers, etc.), one or more communication buses or other components. According to an embodiment, the system controller 312 is coupled to the user interface 380, the RF signal source 320, and the sensor 390 (if included). The system controller 312 may provide control signals to the power and bias circuitry 326 and the RF signal source 320. In addition, the system controller 312 provides control signals to the variable impedance matching network 370 that cause the network 370 to change its state or configuration.

The defrost chamber 360 includes a capacitive defrost arrangement having a first parallel plate electrode and a second parallel plate electrode separated by an air chamber within which a load 364 to be defrosted can be placed. For example, the first repositionable electrode 340 may be positioned over an air cavity, and the second repositionable electrode 372 may be positioned under the air cavity. More specifically, the receiving structure 366 may include a bottom wall, a top wall, and side walls that define a cavity 360 (e.g., the cavity 110 of fig. 1) and an inner surface of a door or hatch for receiving the structure 366. The support structures 322 can be disposed on the sidewalls of the receiving structure 366, and the repositionable shelf 323 including the first electrode 340 and the repositionable shelf 324 including the second electrode 372 can be selectively placed (e.g., by a user) on different pairs of support structures 322, which allows the size of the air cavity between the first electrode 340 and the second electrode 372 to be varied (e.g., to accommodate different sized loads). According to an embodiment, the cavity 360 may be sealed (e.g., with the door 116 of fig. 1) to accommodate electromagnetic energy introduced into the cavity 360 during defrost operations. The system 300 may include one or more interlock mechanisms that ensure that the seal is intact during the defrost operation. The system controller 312 may stop the defrost operation if one or more of the interlock mechanisms indicate that the seal is broken. According to an embodiment, the receiving structure 366 is at least partially formed of an electrically conductive material, and one or more electrically conductive portions of the receiving structure 366 may be grounded. Additionally, in some embodiments, the second repositionable electrode 372 may be electrically coupled to the grounded receiving structure 366 via a busbar (e.g., busbar 126 of fig. 1, busbar 504 of fig. 5) located on a wall (e.g., rear wall 115 or side walls 113, 114 of fig. 1) of the receiving structure 366. Alternatively, the second repositionable electrode 372 may be electrically coupled to the grounded receiving structure 366 through the support structure 322. In an alternative embodiment, the second repositionable electrode 372 may be electrically coupled to a separate ground via a bus bar, and the support structure 322 may be non-conductive and may insulate the electrode 372 from the receiving structure 366. To avoid direct contact between the load 364 and the top surface of the second repositionable electrode 372, a non-conductive barrier 362 may be positioned over the second repositionable electrode 372.

Basically, the defrost chamber 360 includes a capacitive defrost arrangement having a first parallel plate electrode 340 and a second parallel plate electrode 372 separated by an air chamber within which a load 364 to be defrosted can be placed. In one embodiment, the second repositionable electrode 372 is positioned within the receiving structure 366 to define a distance 352 between opposing surfaces of the first repositionable electrode 340 and the second electrode 372, wherein the distance 352 is at least equal to the minimum distance required to receive the load 364.

In various embodiments, distance 352 is in the range of about 0.10 meters to about 1.0 meter, although distances may be smaller or larger. The distance 352 may change (e.g., to accommodate loads of different magnitudes) as the repositionable shelves 323 and 324 are moved to rest on different pairs of support structures 322.

First repositionable electrode 340 and second repositionable electrode 372 can be capacitively coupled when an RF signal is applied to electrode 340 by RF signal source 320. More specifically, the first repositionable electrode 340 can be analogized to a first plate of a capacitor, the second repositionable electrode 372 can be analogized to a second plate of a capacitor and the load 364, barrier 362, and air within the cavity 360 between the electrode 340 and the electrode 372 can be analogized to a capacitor dielectric.

Essentially, the voltage across the first repositionable electrode 340 and the second repositionable electrode 372 heats the load 364 within the chamber 360. According to various embodiments, the RF subsystem 310 is configured to generate RF signals to produce a voltage between the first and second repositionable electrodes 340, 372 that is in the range of about 90 volts to about 3,000 volts in one embodiment, or in the range of about 3000 volts to about 10,000 volts in another embodiment, although the system may also be configured to produce lower or higher voltages between the first and second repositionable electrodes 340, 372.

The first repositionable electrode 340 is electrically coupled to the RF signal source 320 via the variable impedance matching network 370 and the conductive transmission path 328, which may include a plurality of conductors, the conductive transmission path 328. According to an embodiment, the conductive transmission path 328 is an "unbalanced" path configured to carry an unbalanced RF signal (i.e., a single RF signal referenced with respect to ground). In some embodiments, one or more connectors (not shown, but each having a male connector portion and a female connector portion) may be electrically coupled along transmission path 328, and a portion of transmission path 328 between the connectors may include a coaxial cable or other suitable connector.

In one embodiment, the variable impedance matching network 370 may include an arrangement of variable passive components and (optionally) non-variable passive components, such as resistors, capacitors, and/or inductors. The variable impedance matching network 370 may be configured to perform an impedance transformation of the output impedance (e.g., about 10 ohms) from the RF signal source 320 to "match" the input impedance (e.g., about hundreds or thousands of ohms, such as about 1000 ohms to about 4000 ohms or more) of the defrost chamber 360 as modified by the load 364. As the temperature of the load 364 increases during defrost operations, the impedance of the defrost chamber 360 plus the load 364 will change. The system controller 312 may thus adjust the impedance of the variable impedance matching network 370 during defrost operations to account for changes in the impedance of the defrost chamber 360. In some embodiments, the system controller 312 may perform this adjustment of the variable impedance matching network 370 in response to detecting that the S11 parameter of the system has exceeded a predetermined threshold (e.g., using power detection circuitry, not shown, disposed along path 328).

The RF signal source 320 is configured to generate an oscillating electrical signal in response to a control signal provided by the system controller 312 over connection 314. In various embodiments, the RF signal source 320 may be controlled to generate oscillating signals at different power levels and/or different frequencies. For example, the RF signal source 320 may generate a signal that oscillates in a range of about 10.0 megahertz (MHz) to about 100MHz and/or about 100MHz to about 3.0 gigahertz (GHz).

In the embodiment of fig. 3, RF signal source 320 may include a plurality of amplifier stages, such as a driver amplifier stage and a final amplifier stage, to produce an amplified output signal. For example, the power level of the output signal of the RF signal source 320 may be in the range of about 100 watts to about 400 watts or more.

The gain applied by the power amplifier may be controlled using the gate bias voltage and/or the drain supply voltage provided to the one or more amplifier stages by the supply and bias circuitry 326. More specifically, the power supply and bias circuitry 326 provides a bias voltage and a supply voltage to each RF amplifier stage according to control signals received from the system controller 312.

In one embodiment, RF signal source 320 includes laterally diffused metal oxide semiconductor fet (ldmosfet) transistors configured to amplify an input RF signal to provide the RF signal to variable impedance matching network 370. However, it should be noted that the transistors are not intended to be limited to any particular semiconductor technology, and in other embodiments, each transistor may be implemented as a gallium nitride (GaN) transistor, another type of MOSFET transistor, a Bipolar Junction Transistor (BJT), or a transistor utilizing another semiconductor technology.

The defrost chamber 360 and any load 364 (e.g., food, liquid, etc.) positioned within the defrost chamber 360 present a cumulative load to the electromagnetic energy (or RF power) radiated into the chamber 360 by the first electrode 340. More specifically, the cavity 360 and the load 364 present an impedance to the system, which is referred to herein as the "cavity input impedance". During defrost operations, the chamber input impedance changes as the temperature of load 364 increases.

Power is supplied to the RF signal source 320 through power supply and bias circuitry 326. The power and bias circuitry 326 typically outputs a Direct Current (DC) voltage to the RF signal source 320, where the DC voltage may be in the range of 0 volts to 65 volts. The magnitude of the DC voltage output by the power supply and bias circuitry 326 may be set or determined by the system controller 312. For example, based on inputs received from the user interface 380 and the sensor 390, the system controller 312 may select an appropriate output voltage for the power supply and bias circuitry 326. For example, the output voltage of a heavier load 364 may be greater than a lighter load. Based on these various inputs, the system controller 312 may utilize a look-up table to determine an appropriate output voltage for the power supply and bias circuitry 326. In some embodiments, the system controller 312 may cause the output voltage of the power and bias circuitry 326 to vary throughout the defrost process for a particular load 364.

To implement the different output DC voltages of the power and bias circuitry 326, the power and bias circuitry 326 may be configured as a variable power supply capable of generating and outputting these different output voltages. However, in other embodiments, the power supply and bias circuitry 326 may be configured to generate a fixed output voltage. In this case, the defrost system 300 may incorporate a pulse width modulation circuit configured to modulate the fixed output voltage into a variable output voltage (e.g., a voltage ranging from 0 volts to 65 volts) that may be used to operate the RF signal source 320 and implement the functions of the defrost system 300.

Fig. 3 and the related discussion describe an "unbalanced" defrost apparatus in which an RF signal is applied to one repositionable electrode (e.g., the first repositionable electrode 340 of fig. 3) while the other repositionable electrode (e.g., the second repositionable electrode 372 of fig. 3) is grounded. In other embodiments, the RF signal and ground may be applied to opposite electrodes (e.g., the RF signal is applied to the second repositionable electrode 372 and the first repositionable electrode 340 is grounded). As mentioned above, alternative embodiments of the defrost device include a "balanced" defrost device. In such an apparatus, RF signals are provided to the two repositionable electrodes.

For example, fig. 4 is a simplified block diagram of an equilibrium defrost system 400 (e.g., the defrost system 100 of fig. 1, the defrost systems 210, 220 of fig. 2) according to another example embodiment. In one embodiment, the defrost system 400 includes an RF subsystem 410, a defrost chamber 460, a user interface 480, a system controller 412, an RF signal source 420, a power supply and bias circuitry 426, a first repositionable electrode 440 and a second repositionable electrode 472, a support structure 422 disposed on a wall of a containment structure 466, a repositionable shelf 423 that includes the first repositionable electrode 440 and is supported by one pair of support structures 422, and a repositionable shelf 424 that includes the second repositionable electrode 472 and is supported by another pair of support structures 422. In some embodiments, the first and second repositionable electrodes 440 and 472 can include conductive material embedded or disposed on (e.g., in or on) the repositionable shelves 423 and 424, respectively. In other embodiments, the repositionable shelves 423 and 424 may be fully electrically conductive, such that all of the repositionable shelves 423 function as the first repositionable electrode 440 and all of the repositionable shelves 424 function as the second repositionable electrode 472. In still other embodiments, the repositionable shelves 423 and 424 can be wire frames attached to the first and second repositionable electrodes 440 and 472, respectively, and electrically insulated therefrom by standoff isolators (e.g., standoff isolators 530 of fig. 6, 7). Moreover, in other embodiments, the defrost system 400 may include one or more temperature sensors, one or more IR sensors, and/or one or more weight sensors 490, although some or all of these sensor components may not be included. It should be understood that fig. 4 is a simplified representation of the defrost system 400 for purposes of explanation and ease of description, and that practical embodiments may include other devices and components to provide additional functions and features, and/or that the defrost system 400 may be part of a larger electrical system.

The user interface 480 may correspond to a control panel (e.g., the control panel 120 of fig. 1, the control panels 214, 224 of fig. 2), for example, that enables a user to provide input to the system regarding parameters of the defrost operation (e.g., characteristics of the load to be defrosted, etc.), the activate and deactivate buttons, mechanical controls (e.g., door/drawer unlatch), and so forth. Further, the user interface may be configured to provide user perceptible outputs (e.g., a countdown timer, a visual indicia indicating the progress or completion of the defrost operation, and/or an audible tone indicating the completion of the defrost operation) and other information indicating the status of the defrost operation.

In one embodiment, the RF subsystem 410 includes a system controller 412, an RF signal source 420, and power and bias circuitry 426. The system controller 412 may include one or more general-purpose or special-purpose processors (e.g., microprocessors, microcontrollers, ASICs, etc.), volatile and/or non-volatile memory (e.g., RAM, ROM, flash memory, various registers, etc.), one or more communication buses, and other components. According to an embodiment, the system controller 412 is operatively and communicatively coupled to a user interface 480, an RF signal source 420, and power and bias circuitry 426. The system controller 412 is configured to receive signals indicative of user inputs received via the user interface 480 and the one or more sensors 490. In response to the received signals, the system controller 412 provides control signals to the power supply and bias circuitry 426 and/or the RF signal source 420. In addition, the system controller 412 provides control signals to the variable impedance matching network 470 that cause the network 470 to change its state or configuration.

The defrost chamber 460 includes a capacitive defrost arrangement having a first parallel plate electrode 440 and a second parallel plate electrode 472 separated by an air chamber within which a load 464 to be defrosted can be placed. Within the receiving structure 466, the first and second electrodes 440, 472 (e.g., electrodes 170, 172 of fig. 1) are positioned opposite one another on either side of the inner defrost chamber 460 (e.g., the interior chamber 110 of fig. 1).

The first electrode 440 and the second electrode 472 are separated by a distance 452 across the cavity 460. In various embodiments, distance 452 is in a range of about 0.10 meters to about 1.0 meter, although distances may be smaller or larger. The distance 452 may change (e.g., to accommodate loads of different sizes) as the repositionable shelves 423 and 424 are moved to rest on different pairs of support structures 422. When a balanced RF signal is applied by RF signal source 420 to first electrode 440 and second electrode 472, electrodes 440, 472 may capacitively couple. More specifically, the first electrode 440 may be analogized to a first plate of a capacitor, the second electrode 472 may be analogized to a second plate of a capacitor and the load 464, barrier 462, and air within the cavity 460 between the electrodes 440, 472 may be analogized to a capacitor dielectric.

Basically, the load 464 of the voltage heating chamber 460 across the first electrode 440 and the second electrode 472. According to various embodiments, the RF subsystem 410 is configured to generate RF signals to produce a voltage across the electrodes 440, 472 in a range of about 90 volts to about 3000 volts in one embodiment, or about 3000 volts to about 10,000 volts in another embodiment, although the system may also be configured to produce lower or higher voltages across the electrodes 440, 472.

The output of RF subsystem 410, and more specifically the output of variable impedance matching network 470, is electrically coupled to electrodes 440, 472, respectively, via electrically conductive paths 430, 428. For example, RF subsystem 410 may output two balanced RF signals, one signal provided along path 430 to electrode 440 and the other signal provided along path 428 to electrode 472. These balanced RF signals may be generated, for example, as the output of a balun, a push-pull amplifier, or a balanced amplifier that has received an unbalanced RF signal from RF signal source 420.

In one embodiment, the variable impedance matching network 470 may include an arrangement of variable passive components and (optionally) non-variable passive components, such as resistors, capacitors, and/or inductors. The variable impedance matching network 470 may be configured to perform an impedance transformation of the output impedance (e.g., about 10 ohms) from the RF signal source 420 to "match" the input impedance (e.g., about hundreds or thousands of ohms, such as about 1000 ohms to about 4000 ohms or more) of the defrost cavity 460 as modified by the load 464.

The defrost chamber 460 and any loads 464 (e.g., food, liquid, etc.) positioned in the defrost chamber 460 present a cumulative load on the electromagnetic energy (or RF power) radiated into the chamber 460 by the electrodes 440, 472. More specifically, the cavity 460 and the load 464 present an impedance to the system, which is referred to as the cavity input impedance. During defrost operations, the chamber input impedance changes as the temperature of the load 464 increases. The system controller 412 can thus adjust the impedance of the variable impedance matching network 470 during defrost operations to account for the change in impedance of the defrost chamber 460 plus the load 464. In some embodiments, the system controller 412 may perform this adjustment of the variable impedance matching network 470 in response to detecting that the S11 parameter of the system has exceeded a predetermined threshold (e.g., using power detection circuitry, not shown, disposed along paths 428 and/or 430).

The RF signal source 420 is configured to generate an oscillating electrical signal in response to a control signal provided by the system controller 412 over connection 414. In various embodiments, the RF signal source 420 may be controlled to generate oscillating signals at different power levels and/or different frequencies. For example, the RF signal source 420 may generate a signal that oscillates in a range of about 10.0MHz to about 100MHz and/or about 100MHz to about 3.0 GHz.

In the embodiment of fig. 4, the RF signal source 420 may include a plurality of amplifier stages, such as a driver amplifier stage and a final amplifier stage, to generate an amplified output signal. For example, the power level of the output signal of the RF signal source 420 may be in the range of about 100 watts to about 400 watts or more.

The gain applied by the power amplifier may be controlled using the gate bias voltage and/or the drain supply voltage provided to each amplifier stage by the supply and bias circuitry 426. More specifically, the power supply and bias circuitry 426 provides a bias voltage and a supply voltage to each RF amplifier stage according to control signals received from the system controller 412.

In one embodiment, the RF signal source 420 may include transistors having different designs that are not limited to any particular semiconductor technology. Such transistors may include LDMOS transistors, GaN transistors, other types of MOSFETs, BJTs or transistors utilizing another semiconductor technology.

Power is supplied to the RF signal source 420 through power supply and bias circuitry 426. The power and bias circuitry 426 typically outputs a DC voltage to the RF signal source 420, where the DC voltage may be in the range of 0 volts to 65 volts. The magnitude of the DC voltage output by the power supply and bias circuitry 426 may be set or determined by the system controller 412. For example, based on inputs received from the user interface 480 and the sensor 490, the system controller 412 may select an appropriate output voltage for the power supply and bias circuitry 426. For example, the output voltage of the heavier load 464 may be greater than the heavier load. Based on these various inputs, the system controller 412 may utilize a look-up table to determine an appropriate output voltage for the power supply and bias circuitry 426. In some embodiments, the system controller 412 may cause the output voltage of the power and bias circuitry 426 to vary throughout the defrost process for a particular load 464.

To implement the different output DC voltages of the power and bias circuitry 426, the power and bias circuitry 426 may be configured as a variable power supply capable of generating and outputting these different output voltages. However, in other embodiments, the power supply and bias circuitry 426 may be configured to generate a fixed output voltage. In this case, the defrost system 400 may incorporate a pulse width modulation circuit configured to modulate the fixed output voltage into a variable output voltage (e.g., a voltage ranging from 0 volts to 65 volts) that may be used to operate the RF signal source 420 and implement the functions of the defrost system 400.

Fig. 5 shows an illustrative defrost system 500 (e.g., defrost system 300 of fig. 3, defrost system 400 of fig. 4), sometimes referred to herein as a "thermal augmentation system," which illustrative defrost system 500 may be operated to defrost or otherwise augment a temperature of a load placed between an upper repositionable electrode 540 (e.g., electrode 170 of fig. 1, electrode 340 of fig. 3, electrode 440 of fig. 4, sometimes referred to as a first repositionable electrode) and a lower repositionable electrode 550 (e.g., electrode 172 of fig. 1, electrode 372 of fig. 3, electrode 472 of fig. 4, sometimes referred to as a second repositionable electrode) within a cavity 560 (e.g., cavity 110 of fig. 1, cavity 360 of fig. 3, cavity 460 of fig. 4) defined by a containment structure 566 (e.g., containment structure 366 of fig. 3, containment structure 466 of fig. 4). As shown, the lower surface of the upper repositionable electrode 540 may face the upper surface of the lower repositionable electrode 550, such that the electrodes are arranged in parallel plates. It should be noted that in embodiments where the system 500 is an unbalanced defrost system, the lower repositionable electrode 550 may be removed and the bottom wall (e.g., floor) of the containment structure 566 may be electrically grounded and may serve as the lower electrode. Alternatively, the upper repositionable electrode 540 may be removed and a top wall (e.g., top plate) of the receiving structure 566 may be electrically grounded and may serve as the upper electrode.

As shown, the busbars 502 and 504, repositionable shelves 522 and 524 (e.g., the repositionable shelves 522 and 524 may be solid or wire racks), and support structures 516 and 518 (e.g., the support structures 516 and 518 may be conductive or insulating rails attached to, integrally formed with, or otherwise disposed on the sidewalls of the cavity 560) may also be located in the cavity 560. Busbar 502 may be mounted or otherwise disposed on rear inner wall 510 (or another wall) of containment structure 566 and may include a plurality of ports 506 disposed along the length of busbar 502. Similarly, the busbar 504 may be mounted or otherwise disposed on the rear inner wall 510 (or another wall) of the containment structure 566 and may include a plurality of ports 508 disposed along the length of the busbar 504. In some embodiments, the busbars 502 and 504 may instead be positioned outside of the cavity 560. For example, the bus bars 502 and 504 may be disposed on or at an outer surface of the rear inner wall 510 (i.e., outside of the cavity 560), and the ports 506 of the bus bars 502 and the ports 508 of the bus bars 504 may be aligned with corresponding holes in the rear inner wall 510, such that the bus bars 502 and 504 may be connected to the electrodes 540 and 550.

The electrodes 540 and 550 are repositionable in that the electrodes 540 and 550 can be placed at various selectable positions (e.g., heights) within the containment structure 566 by engaging the electrodes 540, 550 with different sets of corresponding ports 506, 508, which allows for flexibility in selecting the location in the containment structure 566 where the defrost operation will be performed and in adjusting the distance between the electrodes 540 and 550 to accommodate loads of different sizes. The selectable positions may be discrete (e.g., defined by the positions of support structures 516 and 518 and ports 506 or 508). For example, the upper and lower repositionable electrodes 540, 550 may be individually removed and reinserted into different locations within the cavity 560, such that different sized loads may be accommodated between the electrodes 540, 550, and such that a user may minimize the distance between the electrodes 540, 550 (or the distance between the upper surface of the load and the upper electrode 540) when accommodating a given load. Selectively positioning electrodes 540 and 550 in this manner may result in better defrost efficiency for system 500. As used herein, "minimizing" the distance between electrode 540 and electrode 550 refers to disposing electrodes 540 and 550 in cavity 560 so as to reduce the distance between electrode 540 and electrode 550 to a reasonably small distance, wherein electrode 540 may be repositioned proximate to a load, ideally without requiring physical contact with the load.

While the repositionable nature of electrodes 540 and 550 allows for improved defrosting efficiency of system 500 via minimizing the distance between electrode 540 and electrode 550, it should be noted that such minimization is typically at the discretion of the user. Thus, some users may unknowingly reduce the defrosting efficiency of the system 500 when attempting to increase the temperature of the load at a relatively small height, for example, by placing the electrodes 540 and 550 in the cavity 560 such that the distance between the upper repositionable electrode 540 and the lower repositionable electrode 550 is significantly greater than the height of the load (e.g., exceeds a predetermined threshold). In this scenario, cavity 560 may appear empty to system 500. For example, the system may identify the cavity 560 as empty or having an incorrectly positioned electrode when the cavity impedance, as observed by the system 500, corresponds to a predetermined impedance (or impedance range) associated with the cavity (e.g., a cavity impedance threshold or range stored in a memory of the system 500). When the system 500 detects that the impedance of the chamber 560 plus the load corresponds to the impedance of the cavity, the system 500 may provide a warning to the user that the chamber is empty or that the electrodes 540 and 550 should be repositioned (e.g., placed closer).

The electrodes 540, 550 and the bus bars 502, 504 have corresponding connector portions configured to engage with each other to hold the electrodes 540, 550 in a fixed position relative to the bus bars 502, 504. For example, the corresponding connector portions may include plugs that couple to the electrodes 540, 550 and the aforementioned ports 506, 508 within the busbar 502, 504. To position the upper repositionable electrode 540 in a selected position within the cavity 560, the electrode 540 may be aligned with one of the ports 506 such that a plug (e.g., a banana plug) of the upper repositionable electrode 540 may be inserted into the port. Similarly, one of the ports 508 of the busbar 504 may receive a plug of the lower repositionable electrode 550 when the lower repositionable electrode 550 is positioned in a corresponding location within the cavity. The busbars 502 and 504 may be formed at least in part from a conductive material (e.g., copper, aluminum). As will be described, the electrodes 540 and 550 may be electrically coupled to an RF signal source, a voltage source, a ground terminal, or a combination thereof, depending on the embodiment, by inserting a first connector portion (e.g., a plug) of the electrodes 540 and 550 into a corresponding second connector portion (e.g., ports 506 and 508, respectively) of the busbar 502, 504. The connection between electrodes 540 and 550 and busbars 502 and 504 may additionally serve to partially or fully physically support electrodes 540 and 550.

The repositionable shelves 522 and 524 may provide additional support for the electrodes 540 and 550, respectively. The repositionable shelf 522 can be attached to the upper repositionable electrode 540 via support bars that extend across the upper repositionable electrode 540 and can be supported at opposite ends by a corresponding first pair of support structures 516 and 518 (e.g., the support structures 322 of fig. 3, the support structures 422 of fig. 4), wherein the corresponding first pair of support structures 516, 518 includes at least one first support structure 516 coupled to the first wall 512 of the chamber 560 and at least one second support structure 518 coupled to the second wall 514 of the chamber 560 at the same height as the one or more first support structures 516. The repositionable shelf 524 may be attached to the lower repositionable electrode 550 via support bars that extend across the lower repositionable electrode 550 and may be supported at opposite ends by a corresponding second pair of support structures 516 and 518, wherein the corresponding second pair of support structures 516, 518 includes at least one third support structure 516 coupled to the first wall 512 of the chamber 560 and at least one fourth support structure 518 coupled to the second wall 514 of the chamber 560 at the same elevation as the one or more third support structures 516. For embodiments in which the repositionable shelves 522 and 524 are wire frames, in some embodiments the support rods of the repositionable shelves 522 and 524 may be formed of an electrically conductive material (e.g., brass, copper, aluminum, or steel), while in other embodiments the support rods may be formed of an electrically insulating dielectric material (e.g., a heat resistant plastic material (e.g., a thermosetting polymer), a ceramic material (e.g., alumina), a fiberglass material (e.g., fiberglass with aluminum-borosilicate glass), and/or mica). The support structure 516 may be attached to or integrally formed with the inner surface of the wall 512 of the receiving structure 566. Support structure 518 may be attached to or integrally formed with another interior surface of wall 514 of receiving structure 566, where wall 512 is opposite wall 514.

In some embodiments, circuitry such as a system controller (e.g., system controller 312 of fig. 3, system controller 412 of fig. 4), power and bias circuitry (e.g., power and bias circuitry 326 of fig. 3, power and bias circuitry 426 of fig. 4), an RF signal source (e.g., RF signal source 320 of fig. 3, RF signal source 420 of fig. 4), and variable and non-variable impedance matching networks (e.g., variable impedance matching network 370 of fig. 3, variable impedance matching network 470 of fig. 4) may be housed in infrastructure 526 disposed below housing structure 566. In some embodiments, a top surface of foundation structure 526 may form a bottom wall of containment structure 566, while in other embodiments, containment structure 566 may have a separate bottom wall that rests on a top surface of foundation structure 526. Bus bars 502 and 504 may extend into infrastructure 526 and may be connected there to a source of RF signals, a voltage source for power and bias circuitry, or ground. In some embodiments, the receiving structure 566 may be electrically grounded, and either of the bus bars 502 and 504 may be electrically connected to ground via a connection to the receiving structure 566. In an alternative embodiment, the circuitry described above may instead be housed in a cavity (not shown) located near the back wall 510, with connections between the circuitry and the cavity being made through openings in the back wall 510. In another alternative embodiment, the circuitry described above may instead be housed in a cavity (not shown) located above the receiving structure 566 and resting on the receiving structure 566, with the connection between the circuitry and the cavity being made through an opening in a top plate (e.g., top wall) of the receiving structure 566.

In some embodiments, one or both of the busbars 502 and 504 may be electrically insulated from the containment structure 566. In such embodiments, a dielectric material (e.g., a heat resistant plastic material such as a thermoset polymer, a ceramic material such as alumina, a glass fiber material such as glass fibers containing an alumino-borosilicate glass, and/or mica) may be interposed between the containment structure 566 and one or both of the bus bars 502 and 504. Additionally or alternatively, the electrically conductive material of the bus bars 502 and 504 may be anodized or otherwise encapsulated in an electrically insulating material to prevent electrical contact between the bus bars 502 and 504 and the rear wall 510 of the containment structure 566. The inner surfaces of the ports 506 and 508 may remain free of anodization or encapsulation so that electrical connection between the ports 506 and 508 and the plugs of the electrodes 540 and 550 may still be made.

In some embodiments (e.g., those in which the rods 542 of the repositionable shelves 522 and 524 are electrically conductive), it may be desirable to prevent physical contact between the repositionable shelves 522 and 524 and the electrodes 540 and 550. Fig. 6 and 7 show perspective views of a system 600 in which electrodes 540 and 550 are attached to repositionable shelves 522 and 524 using standoff spacers 530. The first standoff isolator 530 provides separation between the lower repositionable electrode 550 and the repositionable shelf 524, and the second standoff isolator 530 provides separation between the upper repositionable electrode 540 and the repositionable shelf 522. The standoff separators 530 may be formed in whole or in part from a dielectric material, such as a heat resistant plastic material (e.g., a thermoset polymer), a ceramic material (e.g., alumina), a glass fiber material (e.g., glass fibers comprising an aluminum-borosilicate glass), and/or mica.

As shown in fig. 7 and 8, each standoff isolator 530 can include a cylindrical portion 534 at one end and a threaded portion 538 at an opposite end. The threaded portion 538 may have a diameter smaller than the diameter of the cylindrical portion 534. The cylindrical portion 534 may include a through-hole 544 that extends completely through the cylindrical portion 534. When assembled, one of the rods 542 may be inserted through the through-hole 544 and the threaded portion 538 may be inserted into a hole of the upper repositionable electrode 540 or the lower repositionable electrode 550. The threaded cap 536 may be threaded onto the threaded portion 538 to hold the standoff separator 530 in contact with the upper repositionable electrode 540 or the lower repositionable electrode 550 to secure the standoff separator 530 to the upper repositionable electrode 540 or the lower repositionable electrode 550.

By attaching the electrodes 540 and 550 to the repositionable shelves 522 and 524 with the standoff isolators 530, not only can electrical isolation be achieved between the electrodes 540 and 550 and the repositionable shelves 522 and 524, but capacitive coupling between the electrodes 540 and 550 and the repositionable shelves 522 and 524 can also be reduced by the separation provided by the standoff isolators 530.

Electrodes 540 and 550 may be electrically connected to a source of RF signals, other voltage sources, or electrical ground, depending on whether system 500, 600 provides balanced or unbalanced RF signals to electrodes 540, 550. For example, fig. 9 shows a top-down view of an embodiment in which system 900 provides an unbalanced RF signal to an electrode. The upper repositionable electrode 540 includes a protrusion 546 extending between the main body of the upper repositionable electrode 540 toward the busbar 502. The plug (or other type of first connector portion) of the upper repositionable electrode 540 can be located at one end of the tab 546 and can be electrically connected to the electrode 540. Bus bar 502, and more particularly a port or other connector portion of bus bar 502, may be electrically coupled to electrical ground 547, thereby providing an electrical path to ground for upper repositionable electrode 540 when electrode 540 and the corresponding connector portion of bus bar 502 are physically and electrically coupled together. Alternatively, the busbar 502 may be coupled to a voltage source, which may for example supply a common voltage. In an alternative embodiment, the upper repositionable electrode 540 may be electrically grounded through a direct electrical connection to the wall of the receiving structure 566 rather than through the busbar 502.

The lower repositionable electrode 550 includes a protrusion 545 extending between the main body of the lower repositionable electrode 550 toward the busbar 504. A plug (or other type of first connector portion) of the lower repositionable electrode 550 can be located at one end of the protrusion 545 and can be electrically connected to the electrode 550. The busbar 504, and more particularly a port or other connector portion of the busbar 504, may be electrically coupled to an RF signal source 920 (e.g., the RF signal source 320 of fig. 3) through a variable impedance matching network 970 (e.g., the variable impedance matching network 370 of fig. 3). In this manner, the RF signal generated by RF signal source 920 may be received by lower repositionable electrode 550 through busbar 504 (i.e., through electrode 550 and the corresponding connector portion of busbar 504).

Fig. 10 shows a top-down view of an embodiment in which system 1000 provides balanced RF signals to electrodes 540, 550. The protrusions 546 extend between the bodies of the upper repositionable electrodes 540 toward the busbar 502. The protrusions 545 extend between the main bodies of the lower repositionable electrodes 550 toward the bus bars 504. Each busbar 502 and 504 may be electrically coupled to an RF signal source 1020 (e.g., RF signal source 420 of fig. 4) via a respective path through a variable impedance matching network 1070 (e.g., variable impedance matching network 470 of fig. 4). In this manner, the lower repositionable electrode 550 may receive a first balanced RF signal from the RF signal source 1020 through the busbar 504 when physically and electrically coupled to the busbar 504, and the upper repositionable electrode 540 may receive a second balanced RF signal from the RF signal source 1020 through the busbar 502 when physically and electrically coupled to the busbar 502.

Having described embodiments of the electrical and physical aspects of the defrost system, various embodiments of a method for operating such a defrost system will now be described with reference to fig. 11. More specifically, fig. 11 is a flow chart of a method of operating a defrost system (e.g., the system 100 of fig. 1, the systems 210, 220 of fig. 2, the system 300 of fig. 3, the system 400 of fig. 4, the system 500 of fig. 5, the system 600 of fig. 6, the system 900 of fig. 9, the system 1000 of fig. 10) utilizing dynamic load matching, according to an example embodiment.

In block 1101, when one or more repositionable shelves (e.g., the repositionable shelves 123, 124 of fig. 1, the repositionable shelves 323, 324 of fig. 3, the repositionable shelves 423, 424 of fig. 4, the repositionable shelves 5-6, 9, 10, 522, 524 of fig. 1) are inserted into the defrost cavity (e.g., the cavity 110 of fig. 1, the cavity 360 of fig. 3, the cavity 460 of fig. 4, the cavities 5-6, 9, 560 of fig. 10) of the system at one or more selected locations to interact with the support structures (e.g., the support structure 122 of fig. 1, the support structure 322 of fig. 3, the support structure 422 of fig. 4, 5-6, 9, 10, 516 of fig. 10) disposed on the sidewalls of the containment structures (e.g., the containment structure 366 of fig. 3, the containment structure 466 of fig. 4, 5-6, 9, 566 of fig. 10) of the system, 518) Upon engagement, the method may begin. For example, each repositionable shelf may be poked onto the support structure such that a first connector portion (e.g., a plug) coupled to an electrode of the repositionable shelf (e.g., electrodes 170, 172 of fig. 1, electrodes 340, 372 of fig. 3, electrodes 440, 472 of fig. 4, electrodes 540, 550 of fig. 5-6, 9, 10) is aligned with and inserted into a second connector portion (e.g., ports 506, 508) of a corresponding busbar (e.g., busbar 126, 128 of fig. 1, busbar 502, 504 of fig. 5, 6, 9, 10) disposed on a wall of the receiving structure. The bus bars may be at least partially conductive, and the electrodes may be electrically connected to a ground or RF signal source (e.g., RF signal source 320 of fig. 3, RF signal source 420 of fig. 4, RF signal source 920 of fig. 9, RF signal source 1020 of fig. 10) through the bus bars when inserted into the ports of the bus bars. For example, in an embodiment having two repositionable shelves, a user may insert each repositionable shelf into the receiving structure at a respective selected position such that the amount of empty space between the repositionable shelves is minimized while still leaving enough space for a given size of load to rest on both repositionable shelves with a minimum distance between the top of the load and the upper portions of both repositionable shelves.

At block 1102, a system controller (e.g., the system controller 312 of fig. 3, the system controller 412 of fig. 4) receives an indication that a defrost operation should be initiated. Such an indication may be received, for example, after a user has placed a load (e.g., load 364 of fig. 3, load 464 of fig. 4, load 564 of fig. 5) in a defrost chamber (e.g., chamber 360 of fig. 3, chamber 460 of fig. 4, chamber 560 of fig. 5-6) of the system, sealed the chamber (e.g., by closing a door or drawer), and pressed a start button (e.g., user interface 380 of fig. 3, user interface 480 of fig. 4). In one embodiment, the sealing of the chamber may engage one or more safety interlock mechanisms that, when engaged, indicate that the RF power supplied to the chamber does not substantially leak into the environment outside the chamber. As will be described later, disengagement of the safety interlock mechanism may cause the system controller to immediately pause or terminate the defrost operation.

According to various embodiments, the system controller optionally may receive additional inputs indicative of the load type (e.g., meat, liquid, or other material), the initial load temperature, and/or the load weight. For example, information about the load type may be received from a user through interaction with a user interface (e.g., selection by the user from a list of identified load types). Alternatively, the system may be configured to scan a bar code visible outside the load or receive an electronic signal from an RFID device on or embedded within the load. Information regarding the initial load temperature may be received, for example, from one or more temperature sensors and/or IR sensors (e.g., sensor 390 of fig. 3, sensor 490 of fig. 4) of the system. Information regarding the weight of the load may be received from a user or from a weight sensor of the system (e.g., one of the sensors 390 of fig. 3, 490 of fig. 4) through interaction with a user interface. As indicated above, receipt of inputs indicative of load type, initial load temperature, and/or load weight is optional, and the system may alternatively not receive some or all of these inputs.

In block 1104, the system controller provides control signals to a variable matching network (e.g., network 370 of fig. 3, network 470 of fig. 4, network 970 of fig. 9, network 1070 of fig. 10) to establish an initial configuration or state of the variable matching network. The control signal affects the value of various component values (e.g., inductance, resistance, and/or capacitance) within the variable matching network. For example, the control signal may affect the state of the bypass switch in response to a control signal from the system controller.

Once the initial variable matching network configuration is established, the system controller may perform a process at block 1106 to adjust the configuration of the variable impedance matching network as necessary to find an acceptable or best match based on actual measurements indicative of the quality of the match. According to an embodiment, this process includes having an RF signal source supply a relatively lower power RF signal through a variable impedance matching network to one or more electrodes (e.g., electrodes 340, 372 of fig. 3, electrodes 440, 472 of fig. 4, or electrodes 540, 550 of fig. 5-6). The system controller may control the RF signal power level to the power supply and bias circuitry (e.g., circuitry 326 of fig. 3, circuitry 426 of fig. 4) by control signals that cause the power supply and bias circuitry to provide a supply voltage and a bias voltage to the input of the RF signal source that is consistent with the desired signal power level. For example, a relatively lower power RF signal may be a signal having a power level in the range of about 10W to about 20W, but alternatively, a different power level may be used. It is desirable to match the relatively low power level signal during the tuning process to reduce the risk of damaging the cavity or load (e.g., if the initial match causes high reflected power) and to reduce the risk of damaging the switching components of the variable inductance network (e.g., due to arcing across the switch contacts).

The power detection circuitry of the defrost system then measures the reflected power and, in some embodiments, the forward power along the transmission path (e.g., path 328 of fig. 3, paths 428, 430 of fig. 4) between the RF signal source and the one or more electrodes and provides these measurements to the system controller. The system controller may then determine a ratio of the reflected signal power to the forward signal power and may determine an S11 parameter for the system based on the ratio. In one embodiment, the system controller may store the received power measurements (e.g., the received reflected power measurements, the received forward power measurements, or both) and/or the calculated ratio and/or the S11 parameter for future evaluation or comparison.

The system controller may periodically determine whether the match provided by the variable impedance matching network is acceptable based on the reflected power measurement and/or the reflected to forward signal power ratio and/or the S11 parameter (e.g., the reflected power is below a threshold or the ratio is 10% or less or the measurement or value is advantageously compared to some other criteria). Alternatively, the system controller may be configured to determine whether the match is a "best" match. The "best" match may be determined, for example, by iteratively measuring the reflected RF power (and, in some embodiments, the forward reflected RF power) of all possible impedance matching network configurations (or at least a defined subset of the impedance matching network configurations) and determining whether the configuration yields the lowest reflected RF power and/or the lowest reflected to forward power ratio.

When the system controller determines that the match is not acceptable or not the best match, the system controller may adjust the match by reconfiguring the variable impedance matching network. This may be accomplished, for example, by sending control signals to the variable impedance matching network that cause the network to increase and/or decrease variable component values (e.g., variable capacitances, resistances, and/or inductances) within the network. This reconfiguration of the variable impedance matching network may be repeated until a "best" match is determined.

Once an acceptable or best match is determined, defrost operations may begin via the supply of an RF signal by an RF signal source. For example, the initiation of the defrost operation may include increasing the power of the RF signal supplied by the RF signal source to a relatively higher power RF signal. The system controller may control the RF signal power level to the power supply and bias circuitry by control signals that cause the power supply and bias circuitry to provide a supply voltage and a bias voltage consistent with a desired signal power level to the input of the RF signal source. For example, the relatively high power RF signal may be a signal having a power level in the range of about 50W to about 500W, but alternatively, a different power level may be used.

The power detection circuitry may then periodically measure the reflected power and, in some embodiments, the forward power along the transmission path (e.g., path 328 of fig. 3, path 428, 430 of fig. 4) between the RF signal source and the one or more electrodes and may provide these measurements to the system controller. The system controller may again determine the ratio of the reflected signal power to the forward signal power and may determine the S11 parameter of the system based on the ratio. In one embodiment, the system controller may store the received power measurements and/or calculated ratios and/or S11 parameters for future evaluation or comparison. According to embodiments, the periodic measurements of forward and reflected power may be made at a relatively high frequency (e.g., on the order of milliseconds) or at a relatively low frequency (e.g., on the order of seconds). For example, a fairly low frequency for making periodic measurements may be a rate of measurements every 10 to 20 seconds.

The system controller may determine whether the match provided by the variable impedance matching network is acceptable based on one or more reflected signal power measurements, one or more calculated reflected to forward signal power ratios, and/or one or more calculated S11 parameters. For example, the system controller may make this determination using a single reflected signal power measurement, a single calculated reflected to forward signal power ratio, or a single calculated S11 parameter or may make this determination by averaging (or other calculation) a plurality of previously received reflected signal power measurements, previously calculated reflected to forward power ratios, or previously calculated S11 parameters. For example, to determine whether a match is acceptable, the system controller may compare the received reflected signal power, the calculated ratio, and/or the S11 parameter to one or more corresponding thresholds. For example, in one embodiment, the system controller may compare the received reflected signal power to a threshold, such as 5% (or some other value) of the forward signal power. A reflected signal power of less than 5% of the forward signal power may indicate that the match is still acceptable, while a ratio above 5% may indicate that the match is no longer acceptable. In another embodiment, the system controller may compare the calculated reflected to forward signal power ratio to a threshold of 10% (or some other value). Ratios below 10% may indicate that the match is still acceptable, while ratios above 10% may indicate that the match is no longer acceptable. When the measured reflected power or the calculated ratio or the S11 parameter is greater than the corresponding threshold (i.e., the comparison is unfavorable) indicating an unacceptable match, then the system controller may initiate a reconfiguration of the variable impedance matching network.

When the system controller determines that the match provided by the variable impedance matching network is still acceptable (e.g., the reflected power measurement, the calculated ratio, or the S11 parameter are less than a corresponding threshold or the comparison is favorable) based on one or more reflected power measurements, one or more calculated reflected to forward signal power ratios, and/or one or more calculated S11 parameters, the system may evaluate whether an exit condition has occurred in block 1108. In practice, determining whether an exit condition has occurred may be an interrupted drive process that may occur at any point during the defrost process. However, to include this in the flow diagram of FIG. 11, the process is shown as occurring after block 1106.

In any case, several conditions may warrant stopping the defrost operation. For example, when the safety interlock is broken, the system may determine that an exit condition has occurred. Alternatively, the system may determine that an exit condition has occurred upon expiration of a user-set timer (e.g., via user interface 380 of fig. 3, user interface 480 of fig. 4) or a timer established by the system controller based on an estimate of how long the system controller should perform a defrost operation. In yet another alternative embodiment, the system may detect completion of the defrost operation in other ways.

If an exit condition has not occurred, the defrost operation may continue by returning to block 1106. When an exit condition has occurred, then in block 1110 the system controller interrupts the supply of the RF signal by the RF signal source. For example, the system controller may disable the RF signal source (e.g., RF signal source 320 of fig. 3, RF signal source 420 of fig. 4) and/or may cause the power supply and bias circuitry to stop providing the supply current. In addition, the system controller may send a signal to the user interface that causes the user interface to generate a user-perceptible indicia of an exit condition (e.g., by displaying a "door open" or "complete" or providing an audible tone on the display device). The method may then end.

It should be understood that the order of operations associated with the blocks depicted in fig. 11 correspond to example embodiments and should not be construed as limiting the order of operations to only that shown. Rather, some operations may be performed in a different order and/or some operations may be performed in parallel.

The connecting lines shown in the various figures contained herein are intended to represent example functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in an embodiment of the present subject matter. Furthermore, certain terms may also be used herein for reference purposes only and are therefore not intended to be limiting, and the terms "first," "second," and other such numerical terms referring to structures do not imply a sequence or order unless clearly indicated by the context.

As used herein, "node" means any internal or external reference point, connection point, node, signal line, conductive element, etc., where a given signal, logic level, voltage, data pattern, current, or quantity exists. Furthermore, two or more nodes may be implemented by one physical element (and two or more signals may be multiplexed, modulated, or otherwise distinguished even if received or output at a common node).

The foregoing description refers to elements or nodes or features being "connected" or "coupled" together. As used herein, unless expressly stated otherwise, "connected" means that one element is directly connected to (or directly communicates with) another element, but not necessarily mechanically. Likewise, unless expressly stated otherwise, "coupled" means that one element is directly or indirectly connected to (or directly or indirectly communicates with) another element, but not necessarily mechanically. Thus, while the schematic diagrams shown in the figures depict one exemplary arrangement of elements, additional intervening elements, devices, features, or components may be present in an embodiment of the depicted subject matter.

In an example embodiment, a heat augmentation system having a cavity for receiving a load may include: a first repositionable electrode disposed in the cavity; a first busbar disposed in the cavity, the first repositionable electrode being physically and electrically connectable to the first busbar; a second repositionable electrode disposed in the cavity; a second busbar disposed in the cavity and physically and electrically connectable to the second busbar; a plurality of shelf support structures disposed within the cavity, the plurality of shelf support structures configured to support the first and second repositionable electrodes at a plurality of heights within the cavity; and a radio frequency signal source electrically connected to one or both of the first and second repositionable electrodes via the first and second bus bars, respectively, the radio frequency signal source configured to provide radio frequency energy to one or both of the first and second repositionable electrodes. The first busbar may comprise a first plurality of ports and the second busbar comprises a second plurality of ports, the first repositionable electrode being inserted into one of the first plurality of ports and the second repositionable electrode being inserted into one of the second plurality of ports.

In one embodiment, the heat augmentation system may include a variable impedance matching network coupled between the radio frequency signal source and one or both of the first and second repositionable electrodes and having a variable impedance. The variable impedance matching network is configured to adjust the variable impedance based on one or more parameters of the radio frequency energy selected from reflected power, both forward and reflected power, and/or S11 parameters.

In one embodiment, the heat addition system may include: a first repositionable shelf attached to the first repositionable electrode; and a second repositionable shelf attached to the second repositionable electrode. The first and second repositionable shelves may be supported by the plurality of shelf support structures. The heat adding system may include: a first plurality of standoff isolators attaching the first repositionable shelf to the first repositionable electrode and providing separation between the first repositionable shelf and the first repositionable electrode to electrically isolate the first repositionable shelf from the first repositionable electrode; and a second plurality of standoff isolators attaching the second repositionable shelf to the second repositionable electrode and providing separation between the second repositionable shelf and the second repositionable electrode to electrically isolate the second repositionable shelf from the second repositionable electrode. A standoff isolator of the first plurality of standoff isolators can comprise: a cylindrical portion at a first end of the standoff isolator; a threaded portion at a second end of the standoff isolator opposite the first end, the threaded portion inserted through a hole in the first repositionable electrode; and a threaded cap screwed onto the threaded portion to secure the standoff separator to the first repositionable electrode. The cylindrical portion of the standoff isolator may include a through-hole, and the first repositionable shelf may include a rod extending through the through-hole attaching the standoff isolator to the first repositionable shelf.

In one embodiment, the rf signal source may provide a first balanced rf signal to the first repositionable electrode via the first bus bar and a second balanced rf signal to the second repositionable electrode via the second bus bar.

In one embodiment, the second repositionable electrode may be electrically connected to a ground terminal through the second bus bar.

While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments described herein are not intended to limit the scope, applicability, or configuration of the claimed subject matter in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the described embodiment or embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope defined by the claims, which includes known equivalents and foreseeable equivalents at the time of filing this patent application.