阅读说明：本技术 组合近场和远场天线 (Combined near-field and far-field antenna ) 是由 安东尼·凯斯拉斯 于 2020-03-26 设计创作，主要内容包括：一个例子公开了一种被配置成耦合到导电主表面的组合近场和远场天线,所述组合近场和远场天线包括：被配置成耦合到远场收发器的第一馈电点；被配置成耦合到近场收发器的第二馈电点；第一导电天线表面；第一滤波器,所述第一滤波器具有耦合到所述第一馈电点和所述第一导电天线表面的第一接口,并且具有耦合到所述第二馈电点的第二接口；其中所述第一滤波器被配置成衰减在所述第一导电天线表面和所述远场收发器之间传递的远场信号,以免被所述近场收发器接收；并且其中所述第一滤波器被配置成在所述近场收发器和所述第一导电天线表面之间传递近场信号。(One example discloses a combined near-field and far-field antenna configured to be coupled to a conductive major surface, the combined near-field and far-field antenna comprising: a first feed point configured to be coupled to a far-field transceiver; a second feed point configured to be coupled to a near field transceiver; a first conductive antenna surface; a first filter having a first interface coupled to the first feed point and the first conductive antenna surface, and having a second interface coupled to the second feed point; wherein the first filter is configured to attenuate far-field signals passing between the first conductive antenna surface and the far-field transceiver from being received by the near-field transceiver; and wherein the first filter is configured to pass near field signals between the near field transceiver and the first conductive antenna surface.)

1. A combined near-field and far-field antenna configured to be coupled to a conductive major surface, comprising:

a first feed point configured to be coupled to a far-field transceiver;

a second feed point configured to be coupled to a near field transceiver;

a first conductive antenna surface;

a first filter having a first interface coupled to the first feed point and the first conductive antenna surface, and having a second interface coupled to the second feed point;

wherein the first filter is configured to attenuate far-field signals passing between the first conductive antenna surface and the far-field transceiver from being received by the near-field transceiver; and

wherein the first filter is configured to pass near field signals between the near field transceiver and the first conductive antenna surface.

2. The apparatus of claim 1:

wherein the first conductive antenna surface is a planar plate.

3. The apparatus of claim 1:

wherein the first conductive antenna surface is a planar spiral coil or a non-planar spiral coil.

4. The apparatus of claim 1:

wherein the first conductive antenna surface is a planar spiral structure or a non-planar spiral structure, the first conductive antenna surface having a first end coupled to a set of electronic circuits and a second end that is uncoupled and terminates in free space.

5. The apparatus of claim 4:

wherein the first conductive antenna surface is a monopole far field antenna.

6. The apparatus of claim 5:

wherein the monopole far-field antenna has a length greater than or equal to 1/4 wavelengths of the far-field signal carrier frequency.

7. The apparatus of claim 1:

wherein the first conductive antenna surface is oriented such that far field signal currents are substantially perpendicular to the conductive major surface.

8. The apparatus of claim 1:

characterized by further comprising a coil antenna portion coupled to the near field transceiver and configured as a near field magnetic antenna.

9. The apparatus of claim 1:

wherein the near field signal is about 50MHz or less; and

wherein the far field signal is about 1GHz or higher.

10. The apparatus of claim 1:

wherein the first filter is an RF choke coil.

Technical Field

The present specification relates to systems, methods, apparatus, devices, articles of manufacture, and instructions for an antenna.

Background

Discussed herein are near field electromagnetic induction (NFEMI) based in vivo and in vitro communications and other wireless network devices in which transmitters and receivers couple through magnetic (H) and electrical (E) fields and/or communicate far field using RF plane waves propagating through free space.

Disclosure of Invention

According to an exemplary embodiment, a combined near-field and far-field antenna configured to be coupled to a conductive major surface, the combined near-field and far-field antenna comprising: a first feed point configured to be coupled to a far-field transceiver; a second feed point configured to be coupled to a near field transceiver; a first conductive antenna surface; a first filter having a first interface coupled to the first feed point and the first conductive antenna surface, and having a second interface coupled to the second feed point; wherein the first filter is configured to attenuate far-field signals passing between the first conductive antenna surface and the far-field transceiver from being received by the near-field transceiver; and wherein the first filter is configured to pass near field signals between the near field transceiver and the first conductive antenna surface.

In another exemplary embodiment, the first conductive antenna surface is a planar plate.

In another exemplary embodiment, the first conductive antenna surface is a planar spiral coil or a non-planar spiral coil.

In another exemplary embodiment, the first conductive antenna surface is a planar spiral structure or a non-planar spiral structure having a first end coupled to a set of electronic circuits and a second end uncoupled and terminating in free space.

In another exemplary embodiment, the first conductive antenna surface is a monopole far field antenna.

In another exemplary embodiment, the monopole far-field antenna has a length greater than or equal to 1/4 wavelengths of the far-field signal carrier frequency.

In another exemplary embodiment, the first conductive antenna surface is oriented such that far-field signal currents are substantially perpendicular to the conductive major surface.

In another exemplary embodiment, a coil antenna portion coupled to the near field transceiver and configured as a near field magnetic antenna is also included.

In another exemplary embodiment, the near field signal is about 50MHz or less; the far field signal is about 1GHz or higher.

In another exemplary embodiment, the first filter is an RF choke coil.

In another exemplary embodiment, the first filter is at least one of a ferrite bead, a coil with ferrite material around it, or a parallel circuit tuned to the RF frequency.

In another exemplary embodiment, the first filter has a low pass filter topology or a notch filter topology.

In another exemplary embodiment, the first filter (L) has an inductance of about 12 nH.

In another exemplary embodiment, the transceiver is configured to time-division multiplex the near-field signal with the far-field signal.

In another exemplary embodiment, the transceiver is configured to alternately turn on and off to time-division multiplex the near-field signal with the far-field signal.

In another exemplary embodiment, further comprising a second filter coupled between the first conductive antenna surface and the far field transceiver; wherein the second filter is configured to attenuate near-field signals passing between the first conductive antenna surface and the near-field transceiver from being received by the far-field transceiver; wherein the second filter is configured to pass far-field signals between the far-field transceiver and the first conductive antenna surface.

In another exemplary embodiment, a reference plane is also included; wherein the reference plane is coupled to the far-field transceiver; wherein the reference plane is configured to be located closer to the conductive major surface than the first conductive antenna surface.

In another exemplary embodiment, the electrically conductive major surface is at least one of a human body, an ear, a wrist, or an orifice.

In another exemplary embodiment, the combination antenna is embedded in the earplug and the first conductive antenna surface forms an outer surface of the earplug.

In another exemplary embodiment, further comprising a second conductive antenna surface coupled to the near field transceiver; and wherein the first conductive antenna surface is further from the conductive main structure than the second conductive antenna surface.

The above discussion is not intended to represent each exemplary embodiment or every implementation falling within the present or future scope of the claimed subject matter. The figures and the detailed description that follow also illustrate various exemplary embodiments.

Various exemplary embodiments may be more completely understood in consideration of the following detailed description in connection with the accompanying drawings.

Drawings

FIG. 1 shows a schematic view of aIs an example of a near field electromagnetic induction (NFEMI) antenna.

FIG. 2Is an example of a combined near field and far field antenna.

FIGS. 3A, 3B, 3C and 3DTwo exemplary wireless devices including exemplary combined antennas are shown.

FIG. 4Is an exemplary schematic diagram of an exemplary combined near-field and far-field antenna as either a first wireless device or a second wireless device positioned in a user's ear.

While the disclosure is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. However, it is to be understood that other embodiments are possible in addition to the specific embodiments described. The intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the appended claims.

Detailed Description

NFEMI communication in vivo utilizes non-propagating quasi-static H and E fields. Such in-vivo NFEMI devices include H-field antennas (i.e., magnetic antennas) that are primarily sensitive to magnetic fields and/or primarily activate magnetic fields when driven by electric current. Any E-field component from the H-field antenna is greatly reduced (e.g., -20 to-60 dB, a reduction factor of 0.1 to 0.0008 (10% to 0.08%) depending on the antenna design).

The small loop antenna is an exemplary H-field antenna and includes a loop antenna having a size much smaller than its wavelength of use. The small loop antenna does not resonate at the NFEMI carrier frequency, but is tuned to resonance by an external reactance. In some exemplary embodiments, the current in the small loop antenna has the same value in each position of the loop.

Such in-vivo NFEMI devices also include E-field antennas (i.e., electrical antennas) that are primarily sensitive to electric fields and/or primarily initiate electric fields when driven by voltages. Any H-field component from the E-field antenna is greatly reduced (e.g., -20 to-60 dB, a reduction factor of 0.1 to 0.0008 (10% to 0.08%) depending on the antenna design).

The short-loaded dipole antenna is an exemplary E-field antenna and includes a short dipole sized much smaller than the NFEMI carrier frequency and, in some exemplary embodiments, has additional capacitive structures at both ends.

These near-field quasi-static characteristics are a result of the NFEMI antenna size in combination with its carrier frequency. Most of the near-field energy is stored in the form of magnetic and electric fields, while a small amount of RF energy inevitably propagates in free space.

Near Field Magnetic Induction (NFMI) or Near Field Electrical Induction (NFEI) communication may also be used for such body communication. The magnetic field in NFMI devices does not couple to the body, so such devices can be farther away from the body than NFEMI or NFEI devices, and still ensure communication. However, due to the small size of the magnetic antenna in such NFMI devices, the range of the NFMI device is much shorter than the range of the entire NFEI device. Small antenna geometries are effective for NFMI and NFEMI antennas because they minimize radiated waves in free space.

FIG. 1 shows a schematic view of aIs an example of a near field electromagnetic induction (NFEMI) antenna 100 for use in a wireless device. In this example, antenna 100 is an electromagnetic induction (NFEMI) antenna. In some exemplary embodiments, the antenna 100 includes a coil antenna 105 (i.e., for magnetic fields) and a short loaded dipole 120 (i.e., for electric fields). The coil antenna 105 includes a ferrite core 110 wound with a wire 115. The short dipole 120 includes a first conductive antenna surface 125 and a second conductive antenna surface 130. The antenna 100 feed points 135, 140 are coupled to various transceiver circuitry, such as downstream radio transmitter and receiver integrated circuits (RF-ICs) (not shown here). The bandwidth and resonant frequency of the antenna 100 may use reactive components (e.g., capacitors and inductors) integrated into the radio ICResistor bank).

The short loaded dipole section 120 is responsive to an electrical (E) field. The coil antenna portion 105 is responsive to a magnetic (H) field.

When the NFEMI antenna 100 is in close proximity to a body (e.g., a person, an object, etc.), the magnetic and electric fields will be substantially confined to the body and will not radiate significantly in free space. This enhances the security and privacy of such internet of things communications.

In various exemplary embodiments, antenna 100 operates below 50Mhz or 50Mhz to ensure that the field follows the contours of the body and that far field radiation is greatly reduced.

Some body-wearable devices, such as smartwatches, include far-field communication modules to communicate extracorporeally with other wireless devices, such as smartphones.

The body-wearable device may also include a near-field communication module as part of a body area network, which may include earplugs and various sensors configured to be placed proximate to a user's body. Such sensors can collect physical parameters that are transmitted to the smart watch by the near field, even when the user is listening to music that flows from the smart phone to the smart watch and then to the earplugs.

However, in some body area network applications, the user may not be equipped with a smart watch or smart wristband. In such a case, another body-wearable device would need to include a far-field communication module to wirelessly communicate with the smartphone and/or other extracorporeal device. Including a far field communication module in an ear plug may be problematic because the form factor of the ear plug is preferably very small.

Discussed now are exemplary embodiments of a body wearable device that combines near-field and far-field antennas. Such a combined antenna reuses part of the near field antenna for far field communication, so that no or minimal additional volume is needed, so that both antennas fit the form factor of a small earplug.

Exemplary embodiments of such a combined/dual mode antenna may include a first mode for near field audio and data communications and a second mode (e.g., bluetooth, BLE, etc.) for far field communications. Such a combined antenna allows for in vivo and in vitro wireless communication of audio, video and data.

FIG. 2Is an example 200 of a combined near field and far field antenna. The combination antenna 200 includes the elements of the NFEMI antenna 100 (i.e., the ferrite core 110 wound by the conductive wire 115 to form a near-field magnetic antenna, and the first and second electrically conductive antenna surfaces 125, 130 forming a near-field electrical antenna).

The feed points 135, 140 are coupled to a near field transceiver 202, which in various exemplary embodiments, the near field transceiver 202 includes a radio transmitter and receiver integrated circuit (RF-IC) and various reactive components (e.g., capacitance and resistance sets) for adjusting the NFEMI antenna 100 bandwidth and resonant frequency.

Example 200 the combined near-field and far-field antenna further includes a far-field transceiver 204, a first filter (L)206 (e.g., an RF choke coil or a combination of a coil and a capacitor), a second filter 208, a reference plane 210, and feed points 212, 214, 216.

The first conductive antenna surface 125 serves as both near-field E-field coupling and far-field coupling for RF plane waves propagating through free space. In various exemplary embodiments, the first conductive antenna surface 125 may be a planar plate, a planar coil, a spiral coil, or a helical coil.

In some exemplary embodiments, the dual-use first conductive antenna surface 125 is as far away as possible from the first conductive structure (e.g., the user's skin) to improve near-field electrical (E-field) performance while reducing absorption of far-field RF signals by the user's body. In some examples, the first conductive antenna surface 125 may also be oriented such that the far-field antenna current is substantially perpendicular to the conductive major surface (e.g., the user's head).

A first interface of the first filter 206 is coupled to the first conductive antenna surface 125 and the feed point 212 from the far-field transceiver 204, while a second interface of the first filter (L)206 is coupled to the feed point 135.

In the near field mode at lower frequencies (e.g., 10MHz), the first filter (L)206 is low impedance, and the near field transceiver 202 electrically "sees" only the coil antenna portion 105 (small loop antenna, H-field) and the short-loaded dipole portion 120 (i.e., electrical (E) field), as described in fig. 1. The second filter 208 is configured to attenuate near-field transceiver 202 signals from the far-field transceiver 204.

In the far-field mode at higher frequencies (e.g., 2.4GHz), the first filter (L)206 is high impedance and the far-field transceiver 204 only electrically "sees" the first conductive antenna surface 125 and prevents far-field signals from leaking into the near-field transceiver 202.

In some exemplary embodiments, the first filter (L)206 has an inductance of about 12nH for a dual mode system, with 10.6MHz for near field communication frequencies and 2.5GHz (e.g., BT or BLE) for far field communication frequencies.

The first filter (L)206 may be a normal induction coil, a ferrite bead, a coil with ferrite material around it, a "parallel circuit" tuned to the RF frequency. The first filter (L)206 may have a low pass filter or notch filter configuration.

A second filter 208 (e.g., comprising RF matching and near-field filtering circuitry) is coupled between the feed point 212 and the far-field transceiver 204 through a feed point 214. The second filter 208 also isolates the far-field transceiver 204 from the near-field transceiver 202 near-field signals. The second filter 208 may have a high pass filter or a notch filter configuration.

In an exemplary embodiment where the far-field transceiver 204 has balanced input/output, a balancing unit (BALUN) is inserted between the far-field transceiver 204 and the second filter 208.

In some example embodiments, the second filter 208 may be deleted if the near-field and far-field communications are time-multiplexed (i.e., do not occur at the same time). Various shielding may alternatively be added to suppress any signal harmonic interference between the two transceivers 202, 204. The transceivers 202, 204 may be alternately turned on and off to prevent interference.

Far-field transceiver 204 is coupled to reference plane 210 (e.g., of a printed circuit board) by a feed point 216. In some exemplary embodiments, the reference plane 210 is in a position to shield far-field interference (e.g., for an ear bud device, the reference plane 210 may be located distal to the inner ear canal).

In some examples, the reference plane 210 is placed at a maximum distance from the first conductive antenna surface 125 to minimize any capacitance between the reference plane 210 and the first conductive antenna surface 125. A dielectric material (e.g., PCB, plastic with a low dielectric constant, air cavity, etc.) may also be placed between the first surface 125 and the reference plane 210.

FIGS. 3A, 3B, 3C and 3DTwo exemplary wireless devices 300, 326 are shown including exemplary combined antennas. In an exemplary embodiment, the wireless device 300, 326 is an ear plug that may be partially or fully covered in use, for example when placed in an ear plug in the ear canal of a user.

FIG. 3AIs an exemplary side view 302 of a first wireless device 300 having a continuous first conductive antenna surface 316,FIG. 3BIs an exemplary axial view 304 of the first wireless device 300 (i.e., facing the side opposite the ear canal) with a continuous first conductive antenna surface 316.

The device 300 includes a non-planar outer surface 305 having a core region 306 and an extension region 308, a speaker 309, a user interface 310, a coil antenna 312 (i.e., a magnetic H-field antenna), a second conductive antenna surface 314 (i.e., an electric E-field antenna), a first conductive antenna surface 316 (i.e., an electric E-field antenna), a battery 318, and electronic circuitry 320 including a carrier (e.g., a printed circuit board).

The core region 306 in the illustrated example accommodatesFIGS. 2 and 3AVarious functional components are shown. The extension 308 defines a portion of the non-planar outer surface 305 of the wireless device 300 and is contoured to the non-planar surface of the primary conductive surface (e.g., the user's ear to provide stable positioning of the earbud embodiment of the wireless device 300).

In some exemplary embodiments, the speaker 309 is configured to be inserted into the ear canal of a user. The user interface 310 enables control of the wireless device 300 (e.g., controlling different functions of the ear buds), and may include switches, proximity, and/or light-electricity responsive to touch and/or gestures from a user.

Some exemplary embodiments of the coil antenna 312 include a core and wire windings, wherein the core is a ferrite material having dimensions of 2mm diameter and 6mm length, and there are at least 20 wire windings.

In some exemplary embodiments, the second conductive antenna surface 314 includes a lower portion 322 inside the wireless device 300 near the battery and an upper portion 324 closer to the outer surface of the wireless device 300. In some examples, the first conductive antenna surface 316 surrounds the user interface 310, while in other examples, the first conductive antenna surface 316 may have a planar portion that is continuous behind or in front of the user interface 310.

In some exemplary embodiments, the first and second conductive antenna surfaces 314, 316 are flexible metal foils, and in other exemplary embodiments, the first and second conductive antenna surfaces 314, 316 are conductive paint.

The battery 318 provides power to the electronic circuitry 320 and may be recharged or replaced. In various exemplary embodiments, the electronic circuit 320 includes a transceiver circuit, a receiver integrated circuit (RF-IC), and reactive components (e.g., capacitors and resistor banks). The reactive components (e.g., capacitance and resistance sets) adjust the bandwidth and resonant frequency of the device 300. The electronic circuit 320 may be coupled to a substrate/carrier. The carrier may be a printed circuit board or any flexible material suitable for holding the electronic circuit 320 and any mechanical component capable of performing the function of the ear bud.

FIG. 3CIs an exemplary side view 328 of the second wireless device 326 having a spiral/helical first conductive antenna surface 316, andFIG. 3DIs an exemplary axial view 330 (i.e., facing the side opposite the ear canal) of the second wireless device 326 having a spiral/helical first conductive antenna surface 316.

In the exemplary second wireless device 326, the first conductive antenna surface 316 is a planar spiral structure or a non-planar spiral structure having a first end 332 coupled to the electronic circuitry 320 (or coil antenna 312) and a second end 334 that is uncoupled and terminates in free space by forming a monopole RF antenna. A spiral/helical shape can be achieved within the plastic shell of the earplug. In some exemplary embodiments, the distance between the first end 332 and the second end 334 is selected to have a length sufficient to resonate far field communication frequencies between 1 and 6 GHz.

Other particular shapes of the first conductive antenna surface 316 are possible. In a spiral embodiment, the first conductive antenna surface 316 may begin to spiral out from near the user's head in various directions. The helical wire may be very thin to create a very long far field monopole antenna for more robust far field communication. More than one such helical wire may also be used in a nested configuration or in different geometric planes.

In the near field mode, the voltage transmitted and/or received by the NFEMI antenna of the wireless device 300 is a combination of voltages caused by the magnetic H field and the electric E field.

By geometrically conforming the second conductive antenna surface 314 to a major surface (e.g., the ear canal of a user), the antenna capacitance (Ca) increases. Therefore, by conforming to the shape of the extension region 308 of the user's outer ear and the shape of the portion of the magnetic core region 306 next to the speaker 309 conforming to the user's inner ear, the capacitance (Ca) of the NFEMI antenna is increased and a larger electric field is generated.

Thus, the larger capacitance (Ca) enables the dominant electrical surface (e.g., the body of the user) to indirectly transmit the electric field of the second conductive antenna surface 314 even though the direct electric E-field generated by the second conductive antenna surface 314 is blocked by the inner ear.

Also, in the near field mode, by maximizing the distance (d) between the second conductive antenna surface 314 and the first conductive antenna surface 316, a larger electric field is generated and the received voltage (Vrx) is further increased.

Using these two techniques, robustness of near field mode NFEMI communication is achieved.

In the far field mode, the three-dimensional spiral winding or planar spiral winding of the first conductive antenna surface 316 produces a long (e.g., equal to or greater than 1/4 wavelengths) RF antenna for enhanced far field radiation.

The electrical vector produced by winding 316 has the same orientation as the orientation of the current flowing through winding 316. When the first conductive antenna surface 316 is positioned perpendicular to the skin of the head (for an earbud), the current has an orientation perpendicular to the skin. The currents parallel to the skin cancel each other out because the current in front of the coil is 180 degrees different from the current behind the coil.

In some exemplary embodiments, the gain of the antenna is between-15 and-5 dBi at 2.5 GHz. This is due to the low radiation resistance (1 to 5ohms) and the low absorption of the conductive main surface of e.g. human tissue. However, for a 0dBm transmitter output, if you have a sensitive receiver (e.g., -92dBm), this is sufficient for a communication range of 10 to 15 meters.

FIG. 4Is an exemplary schematic diagram 400 of an exemplary combined near-field and far-field antenna 200 in a first wireless device 300 or a second wireless device 326 positioned proximate a first conductive major surface 402 (e.g., a user's head), a second conductive major surface 404 (e.g., a user's outer ear), and/or a third conductive major surface 406 (e.g., a user's inner ear).

In an exemplary embodiment, the speaker 309 is inserted into the inner ear canal 406 of the user 402 and the first conductive structure 314 is mounted proximate to the inner ear canal 406 and the outer ear canal 404 while the second conductive structure 316 is positioned apart from the inner ear. This configuration of the conductive structures 314, 316 provides a combination of close skin contact with the host and maximum separation between the two conductive structures 314, 316.

The conductive major surfaces 402, 404, 406 can generally be any E-field responsive conductive major surface. In various other exemplary embodiments, such conductive major surfaces 402, 404, 406 may be another portion of a human body, a body surface, an aperture, a nose, a mouth, or any type of conductive structure.

Near field signals from the combined antenna 200 are confined near the conductive major surfaces 402, 404, 406 in the transmit mode and are confined by the conductive major surfaces 402, 404, 406 in the receive mode.

In an exemplary embodiment of the near field mode, the near field frequency is kept below 50MHz to ensure that the near field signals follow the contour of the conductive major surfaces 402, 404, 406 and that the first conductive antenna surface 316 radiates only a little far field radiation. However, in far field mode, the first conductive antenna surface 316 is configured to radiate significant far field radiation.

The various instructions and/or operational steps discussed in the above figures may be executed in any order, unless a specific order is explicitly stated. Moreover, those skilled in the art will recognize that while some example sets of instructions/steps have been discussed, the materials in this specification can be combined in a number of ways to produce other examples, and should be understood in the context provided by this detailed description.

In some exemplary embodiments, the instructions/steps are implemented as functions and software instructions. In other embodiments, instructions may be implemented using logic gates, special purpose chips, firmware, and other hardware forms.

When the instructions are implemented as a set of executable instructions in a non-transitory computer-readable or computer-usable medium, the medium is implemented on a computer or machine programmed with and controlled by the executable instructions. The instructions are loaded for execution on a processor (e.g., CPU or CPUs). The processor includes a microprocessor, a microcontroller, a processor module or subsystem (including one or more microprocessors or microcontrollers), or other control or computing devices. A processor may refer to a single component or to multiple components. The computer-readable or computer-usable storage medium may be considered to be part of an article (or article of manufacture). An article or article of manufacture may refer to any manufactured component or components. Non-transitory machine or computer usable media or media as defined herein do not include signals, but such media or media may be capable of receiving and processing information from signals and/or other transitory media.

It will be readily understood that the components of the embodiments, as generally described herein, and illustrated in the accompanying drawings, may be arranged and designed in a wide variety of different configurations. Thus, the detailed description of the various embodiments, as represented in the figures, is not intended to limit the scope of the disclosure, but is merely representative of the various embodiments. While various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized with the present invention should be or are in any single embodiment of the invention. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, discussion of the features and advantages, and similar language, throughout this specification may, but do not necessarily, refer to the same embodiment.

Furthermore, the described features, advantages, and characteristics of the invention may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize, in light of the description herein, that the invention may be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the invention.

Reference throughout this specification to "one embodiment," "an embodiment," or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the phrases "in one embodiment," "in an embodiment," and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.