阅读说明：本技术 小占用面积高性能无源rfid标签 (Passive RFID label with small occupied area and high performance ) 是由 小乔治·戴奇 于 2019-06-17 设计创作，主要内容包括：本发明属于超高频(“UHF”)射频识别(“RFID”)标签的领域。更具体地,本发明总体上涉及用于提供具有小占用面积的无源UHF RFID标签的系统和方法,其被优化以用于新兴的RFID技术市场中的高性能应用。(The present invention is in the field of ultra high frequency ("UHF") radio frequency identification ("RFID") tags. More particularly, the present invention relates generally to systems and methods for providing passive UHF RFID tags with a small footprint, optimized for high performance applications in the emerging RFID technology market.)

1. A passive radio frequency identification ("RFID") tag comprising:

an antenna; and

an integrated circuit having a first total resistance and a second total resistance, the second total resistance being greater than the first total resistance, and configured to selectably switch between the first total resistance and the second total resistance.

2. The passive radio frequency identification tag of claim 1, further comprising a first resistor and a second resistor.

3. The passive radio frequency identification tag of claim 2, wherein the first total resistance is a function of the resistance of the first resistor and the second total resistance is a function of the resistance of the second resistor.

4. The passive radio frequency identification tag of claim 2, wherein the first total resistance is a function of a total resistance of the first and second resistors when connected in parallel, and the second total resistance is a function of a resistance of the first or second resistor.

5. The passive radio frequency identification tag of claim 2, wherein the second total resistance is a function of a total resistance of the first and second resistors when connected in series, and the first total resistance is a function of a resistance of the first or second resistor.

6. The passive radio frequency identification tag of claim 1, further comprising a plurality of resistors, wherein the first total resistance is a function of a total resistance of two or more of the plurality of resistors when connected in parallel.

7. The passive radio frequency identification tag of claim 6, wherein the second total resistance is a function of a resistance of one of the plurality of resistors.

8. The passive radio frequency identification tag of claim 6, wherein the second total resistance is a function of a total resistance of two or more of the plurality of resistors when connected in series.

9. The passive radio frequency identification tag of claim 1, further comprising a plurality of resistors, wherein the second total resistance is a function of a total resistance of two or more of the plurality of resistors when connected in series.

10. The passive radio frequency identification tag of claim 9, wherein the first total resistance is a function of a resistance of one of the plurality of resistors.

11. The passive radio frequency identification tag of claim 9, wherein the first total resistance is a function of a total resistance of two or more of the plurality of resistors when connected in parallel.

12. The passive radio frequency identification tag of claim 1, wherein the integrated circuit has a third total resistance and is configured to selectably switch between the first total resistance, the second total resistance, and the third total resistance.

13. The passive radio frequency identification tag of claim 12, wherein the third total resistance is greater than one or both of the first total resistance and the second total resistance.

14. The passive radio frequency identification tag of claim 12, wherein the third total resistance is less than one or both of the first total resistance and the second total resistance.

15. The passive radio frequency identification tag of claim 12, wherein the third total resistance is greater than the first total resistance and less than the second total resistance.

16. The passive radio frequency identification tag of claim 1, further comprising a radio frequency ("RF") enhancement module.

17. The passive radio frequency identification tag of claim 16, wherein the radio frequency enhancement module comprises one or more capacitors.

18. The passive radio frequency identification tag of claim 16, wherein the radio frequency enhancement module comprises two or more capacitors connected in parallel.

19. A passive radio frequency identification tag comprising:

an antenna; and

an integrated circuit, the integrated circuit comprising:

a radio frequency enhancement module comprising one or more capacitors, an

Two or more resistors configured to selectably switch between a first total resistance and a second total resistance.

20. The passive radio frequency identification tag of claim 19, wherein the radio frequency enhancement module comprises two or more capacitors connected in parallel.

Technical Field

The present invention is in the field of ultra high frequency ("UHF") radio frequency identification ("RFID") tags. More particularly, the present invention relates generally to systems and methods for providing passive UHF RFID tags with a small footprint, optimized for high performance applications in the emerging RFID technology market.

Background

RFID uses magnetic, electric or electromagnetic fields transmitted by the reader system to identify itself and, in some cases, provide additional stored data. RFID tags typically include a semiconductor device, commonly referred to as a "chip" or "integrated circuit," on which memory and operating circuitry are formed. As is known in the art, the integrated circuit is connected to the tag antenna directly or through a device such as an interposer or RFID strap device. Typically, RFID tags are used as transponders to provide information stored in an integrated circuit memory in response to a radio frequency ("RF") interrogation signal received from an RFID reader, also referred to as an interrogator. In the case of an active RFID device, the device has a power source, such as a battery. On the other hand, for passive RFID devices, the energy of the interrogation signal also provides the energy required to operate the RFID device. Thus, while passive RFID devices may have a shorter read range than active RFID devices, they are much cheaper and do not have a limited lifetime (e.g., due to battery life limitations) than active RFID devices. Further, passive RFID devices are typically smaller than active RFID devices because they do not have an onboard power source.

Throughout the world, RFID systems operate in the low frequency ("LF"), high frequency ("HF"), or ultra high frequency ("UHF") bands. Each of these frequency bands has advantages and disadvantages because the behavior of radio waves in each of these frequency bands is different. Systems operating in the higher frequency range typically have faster data transfer rates and longer read ranges and are therefore ideal for many applications.

While LF RFID systems typically run at 125KHz or 134KHz, LF systems cover frequencies from 30KHz to 300 KHz. Although the operating frequency of most HF RFID systems is 13.56MHz, HF systems cover a frequency range of 3MHz to 30 MHz. Finally, although UHF RFID systems typically operate between 860MHz and 960MHz, UHF systems cover a frequency range of 300MHz to 3 GHz. Although there is no consensus on the standardized range of the UHF spectrum, different countries around the world have allocated different parts of the radio frequency spectrum for RFID purposes and have generally adopted standardized uses in LF and HF systems. Thus, UHF systems in europe typically operate between 865MHz to 868MHz, UHF RFID systems in north america typically operate between 902MHz to 928MHz, and UHF systems in china have been approved to operate between 840.25MHz to 844.75MHz and 920.25MHz to 924.75 MHz. Although different tags are required for RFID use in each of the three major RF bands (LF, HF, UHF), the different bands used in UHF RFID systems also require somewhat different tag designs throughout the world, usually by modifying the tag antenna to function in each region.

The main components of a passive UHF RFID tag include a radiating power source from a UHF RFID reader, a conductive antenna, a matching loop, and a UHF RFID integrated circuit or chip, such as a UHF RFID Gen2 integrated circuit. Passive UHF RFID tags collect the power radiated from the RFID reader and transfer the collected power to the integrated circuit through a matching loop to turn the integrated circuit on. Once the integrated circuit is powered up, it may execute the required protocol commands, such as Gen2 protocol commands required by Gen2 integrated circuits.

The chip manufacturer provides standard impedance values at the front end of the integrated circuit. In addition, the new integrated circuit also integrates a self-tuning circuit to provide a limited range of capacitance to find the optimum impedance within a limited range to absorb as much radiated power as possible within a given capacitance range. While helping to account for small variations in impedance due to tag application, the primary benefit is that the sensitivity of the tag can be improved. For example, the tag sensitivity may be increased by about 1dB to about 2 dB. Such self-adjusting circuitry may also assist in the forward linking of the tag, turning on the power to the tag. In addition, this small and limited capacitance range may help expand the response of a small, narrow band RFID tag.

The antenna design also includes a matching loop to provide the required inductance value to match the integrated circuit. The loop circuit is essentially a single loop antenna element, and thus the size of the loop is driven in part by the impedance of the presented integrated circuit and the desired tuning of the application established by the antenna designer. In particular, the antenna design is built to fit a label of a specified size. The label size is typically driven by the size of the product package and the available space on the product package to place the label containing the RFID tag without covering or obscuring the printed content on the product package. Thus, antenna designers typically begin by establishing a loop matching loop that occupies a percentage of the available tag space. The antenna is tuned and matched to the product to be connected to compensate for any potential impact that packaging materials may have on the antenna and to balance the power transfer to the integrated circuit to achieve the read range required by the application.

Passive UHF RFID continues to be deployed worldwide for many applications. In particular, the garment market has been driving significant growth for more than a decade. As technology becomes more popular, new applications continue to emerge. Reader manufacturers will continue to develop their hardware devices to enable new reading points throughout the supply chain and to improve the readability of RFID tags. Chip manufacturers are continually increasing the sensitivity of their chips in each new iteration, thereby increasing the read range of the RFID tags. Antenna designers, such as the Avery Dennison retail information services, inc, of Mentor, ohio, continue to create new antenna designs to match the performance of tags to the application environment.

Although the form factor of the apparel market has not changed fundamentally over the past decade, each new incremental performance increase by chip manufacturers and reader manufacturers has led to an incremental increase in performance of RFID application systems. This incremental increase in system performance results in increased system margins, advantageously making deployed systems more robust, but not necessarily enabling emerging applications.

However, the market for RFID technology, including passive UHF RFID, is entering areas outside of apparel, such as, but not limited to, convenience stores, food applications, aviation, pharmaceuticals, and the like. However, these emerging applications pose significant challenges for current RFID systems because they require fairly small tags that must be read in a high density environment and the effects of product materials vary widely. Furthermore, such tags must not be limited to use only in a specific geographic location, but must be used on a global scale.

Accordingly, there is a need for an RFID tag that is small, can be used on or in conjunction with a variety of materials, has a relatively long read range, and is not limited to use in a particular geographic area.

Disclosure of Invention

The present disclosure relates to UHF RFID tag architectures, which generally include antennas, loops, chips, and constructions. UHF RFID tags advantageously can address emerging applications with unique requirements that were difficult to implement in the past. For example, an emerging market that may be served by the UHF RFID tags of the present disclosure may require a tag with a small size, strong read range that must operate over a wide range of material properties and adapt to its environment globally.

According to some embodiments of the present disclosure, a passive radio frequency identification ("RFID") tag includes: an antenna; and an integrated circuit having a first total resistance and a second total resistance, the second total resistance being greater than the first total resistance, and configured to selectably switch between the first total resistance and the second total resistance.

In some embodiments, the passive RFID tag includes a first resistor and a second resistor. The first resistor and the second resistor may be components of an integrated circuit. In some embodiments, the first total resistance is a function of the resistance of the first resistor and the second total resistance is a function of the resistance of the second resistor. In some embodiments, the first total resistance is a function of a total resistance of the first resistor and the second resistor when connected in parallel, and the second total resistance is a function of a resistance of the first resistor or a resistance of the second resistor. In other embodiments, the second total resistance is a function of a total resistance of the first resistor and the second resistor when connected in series, and the first total resistance is a function of a resistance of the first resistor or a resistance of the second resistor.

According to other embodiments, the passive RFID tag comprises a plurality of resistors, wherein the first total resistance is a function of a total resistance of two or more of the plurality of resistors when connected in parallel. In some embodiments, the second total resistance is a function of the resistance of one of the plurality of resistors. In other embodiments, the second total resistance is a function of a total resistance of two or more of the plurality of resistors when connected in series.

In other embodiments of the present disclosure, the passive RFID tag includes a plurality of resistors, wherein the second total resistance is a function of a total resistance of two or more of the plurality of resistors when connected in series. In some embodiments, the first total resistance is a function of a resistance of one of the plurality of resistors. In other embodiments, the first total resistance is a function of a total resistance of two or more of the plurality of resistors when connected in parallel.

According to some embodiments, the integrated circuit of the passive RFID tag has a third total resistance, and the integrated circuit is configured to selectably switch between the first total resistance, the second total resistance, and the third total resistance. In some embodiments, the third total resistance is greater than one or both of the first total resistance and the second total resistance. In some embodiments, the third total resistance is less than one or both of the first total resistance and the second total resistance. In some embodiments, the third total resistance is greater than the first total resistance and less than the second total resistance.

According to some embodiments, the passive RFID tag includes a radio frequency ("RF") enhancement module. In some embodiments, the RF enhancement module includes one or more capacitors. In some embodiments, the RF enhancement module includes two or more capacitors connected in parallel.

In accordance with other aspects of the present disclosure, a passive RFID tag includes an antenna and an integrated circuit. The integrated circuit may have an RF enhancement module including one or more capacitors and two or more resistors configured to selectably switch between a first total resistance and a second total resistance. In some embodiments, the RF enhancement module includes two or more capacitors connected in parallel.

Drawings

These and other objects and advantages of this invention will be more completely understood and appreciated by referring to the following more detailed description of the presently preferred exemplary embodiments of the invention taken in conjunction with the accompanying drawings, in which:

FIG. 1A depicts a passive RFID tag known in the prior art;

FIG. 1B depicts the major components of a passive RFID tag (such as the tag shown in FIG. 1A);

FIG. 2 depicts components of an RFID system according to certain aspects of the present invention;

FIG. 3 depicts components of an RFID system in accordance with certain aspects of the present invention;

FIG. 4 depicts components of an RFID system in accordance with certain aspects of the present invention;

FIG. 5 depicts an integrated circuit according to some aspects of the present invention;

fig. 6A and 6B depict alternative frequency bands occupied by frequencies;

FIGS. 7A and 7B depict the operation of an RFID tag having broadband matching capabilities in accordance with certain aspects of the present invention;

FIGS. 8A and 8B depict the operation of an RFID tag with narrowband matching capability according to certain aspects of the present invention; and is

Fig. 9 depicts an integrated circuit in accordance with certain aspects of the present invention.

Detailed Description

The apparatus and methods disclosed herein are described in detail by way of example and with reference to the accompanying drawings. Unless otherwise indicated, like numbers in the figures indicate references to the same, similar or corresponding elements throughout the figures. It is to be understood that the disclosed and described examples, arrangements, configurations, components, elements, devices, methods, materials, etc., may be modified and may be desirable for particular applications. In this disclosure, any identification of particular shapes, materials, techniques, arrangements, etc. is in relation to the particular examples presented or is merely a general description of such shapes, materials, techniques, arrangements, etc. The identification of specific details of examples is not intended to, and should not be construed as, mandatory or limiting unless explicitly specified otherwise. Selected examples of apparatus and methods are disclosed and described in detail below with reference to the accompanying drawings.

Thus, it can be seen that in accordance with the present invention, a highly advantageous UHF RFID tag and system has been provided. While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, and that various modifications and equivalent arrangements may be devised within the scope of the present invention which is to be accorded the broadest interpretation of the appended claims to encompass all equivalent structures and products.

As described above, passive RFID tags receive power from a radiating RFID reader. Specifically, the RFID tag antenna collects power from the RFID reader and transmits the power to the integrated circuit through a matching loop (i.e., matching loop). Also as described above, the integrated circuit includes a self-regulating capacitor within a limited range to power the chip.

Referring to fig. 1A and 1B, an exemplary passive RFID tag 100 known in the art is shown. In particular, FIG. 1B illustrates a block diagram showing the major components used with the system 110 for reading RFID tags 100. For example, the system 110 includes an RF power source 112, which is typically provided by an RFID reader (not shown). The RF power source 112 is used to power the RFID tag 100. the RFID tag 100 generally includes a tag antenna 114, such as a dipole antenna including a radiating portion or dipole arm 120, as shown, a matching loop antenna 116 (also referred to herein simply as a "matching loop") and an integrated circuit or RFID chip 118. As shown in FIG. 1A, RFID tag 100 may also include an interposer, such as RFID strap 122, for connecting integrated circuit 118 to matching loop 116. In other embodiments, the integrated circuit 118 may be directly connected to the matching loop 116.

As described above, the matching loop 116 is connected directly or indirectly to the integrated circuit 118 through an interposer, such as an RFID strap 122, to provide the inductance needed to couple the integrated circuit 118 to the tag antenna 114. In particular, the matching loop 116 is used to provide impedance matching between the tag antenna 114 and the integrated circuit 118. Those of ordinary skill in the art will appreciate that the input impedance of the tag antenna 114 may be adjusted by changing the size of the matching loop 116. Thus, when designing the tag antenna 114, the designer must consider the impedance of the selected integrated circuit 118 for a given application to ensure that the matching loop 116 is sized to provide a matched load antenna impedance. As shown in fig. 1A, a portion of the matching loop 116 may overlap the tag antenna 114 to provide greater coupling. While such a configuration may reduce the overall footprint of the RFID tag 110 and increase the efficiency of power transfer, it may result in a narrow band tag. Alternatively, the matching loop 116 may be spaced apart from the tag antenna 114 (not shown).

As mentioned above, new market applications of RFID technology have resulted in market demands for increasingly challenging features and characteristics, such as: smaller RFID tag sizes; an RFID tag with a stronger/longer read range, usable with existing RFID hardware; RFID tags capable of coping with various material influences of products, such as for metal or liquid-containing products; and RFID tags configured to be used globally. Because prior art RFID tags may not be able to meet one or more of these requirements, new passive RFID tag architectures must be used to overcome these challenges.

Many emerging applications require tags of increasingly smaller dimensions. As one example, products sold at convenience stores often require small labels. Such products may include, but are not limited to, healthcare and pharmaceutical products, personal care products, beauty products, skin care products, and other items commonly sold in small packages that may have a large amount of product labeling, where a large RFID tag may not cover the large amount of product labeling. For example, RFID tags for cosmetic products must be small enough to be placed on items with minimal surface area, such as small tubes of lipstick, lip gloss, lipstick, mascara, and the like, as well as pencils or pencil-like items such as eyeliners, eyebrow pencils, lip pencils, and the like.

As the length and/or width of the RFID tag becomes smaller, the surface area of such a tag decreases. As a result, the size of the matching loop that is capable of matching the impedance of the integrated circuit to the load antenna impedance in order to inductively couple the integrated circuit to the tag antenna will occupy a relatively high percentage of the available surface area of the tag. As market applications require smaller and smaller tags, the matching loop size required in a given application may prevent antenna designers from adding more dipole lengths to the tag antenna to optimize other characteristics of the RFID tag. For example, a reduction in antenna size may mean less potential gain and bandwidth.

To overcome any adverse effects of reducing the size of the tag, in some embodiments, the inductance value of the matching loop may be moved into the front-end impedance of the integrated circuit. As a result, the size of the matching loop required to match the integrated circuit impedance to the tag antenna impedance may be reduced. In some embodiments, moving the inductance value to the front-end impedance of the integrated circuit eliminates the need to include a matching loop. Thus, by reducing the size of the matching loop or eliminating the matching loop, a greater surface area is provided over which the tag antenna may be designed.

Referring to fig. 2, the major components of an RFID system 210 are shown, the RFID system 210 being configured to read RFID tags 200, the RFID tags 200 being optimized for a given tag size to increase the size of the tag antenna 214. System 210 may include an RF power supply 212, an antenna 214, a matching loop 216, and an integrated circuit 218. As described above, the inductance value has moved from the tag antenna 214 to the integrated circuit 218. Thus, the integrated circuit 218 may have a reduced size matching loop 216 attached, while the impedance value of the integrated circuit 218 may still match the impedance value of the tag antenna 214.

Another challenge associated with reducing the size of an RFID tag is that it may also reduce the aperture of the tag antenna. However, one of ordinary skill in the art will appreciate that if the tag antenna is less efficient at receiving power, the amount of energy reflected by the tag antenna on the return link will also be reduced. As the reflected energy decreases, the effective read range of the RFID tag also decreases. Thus, successful reading using RFID reader hardware will depend on the hardware's ability to detect weak signals from RFID tags. Therefore, it is generally necessary to provide RFID readers with higher sensitivity at higher cost.

To address this issue, the proposed architecture according to some embodiments of the present disclosure adds capacitance enhancement within the integrated circuit itself. The capacitance enhancement may provide an added charge pump to the integrated circuit, which in turn may enhance the return signal back to the RFID reader hardware. Advantageously, this may provide increased signals to the RFID reader to provide a greater read range, increase system margins in applications, and facilitate readability of the population of RFID tags without requiring an RFID reader with higher sensitivity.

For example, as shown in fig. 3, by providing an integrated circuit 318 for an RF enhancement module 320, an improved energy harvesting integrated circuit 318 may be created. As described above, the RF enhancement module 320 may include one or more capacitors (not shown). In some embodiments, the RF enhancement module 320 includes two or more capacitors connected in parallel. One or more capacitors may be connected to the integrated circuit 318 to store energy harvested from, for example, the RF power source 312, and configured to provide energy to the integrated circuit 318 to enhance the return signal back to the RFID reader (not shown). As shown in fig. 3A, matching loop 316 is provided with tag antenna 314, and RF power source 312 is a component of an RFID reader.

As described above, one disadvantage associated with reducing the size of an RFID tag is that it may reduce the aperture of the tag antenna. However, as the tag antenna aperture decreases, the tag antenna will receive less energy from the RF power radiated by the RFID reader. Thus, as described above, some embodiments of the present invention address this problem by moving the inductance value of the matching loop into the front-end impedance of the integrated circuit to maintain the available surface area of the tag antenna and by increasing the energy harvesting capability within the integrated circuit itself by utilizing capacitance enhancement as described above. Thus, the integrated circuit may provide higher sensitivity and be capable of switching on at lower incident power for a given radiated RF power from the RFID reader.

Referring to fig. 4, one embodiment of the present disclosure illustrates an RFID system 410 for use with an RFID tag 400 having a combination of features disclosed herein to provide increased read range and sensitivity. As shown, by moving the inductance value from the tag antenna 414 to the integrated circuit 218, the smaller matching loop 416 may provide the impedance needed to match the impedance of the tag antenna 414. As a result, the size of the tag antenna 414 may be increased to provide increased RF range. Additionally, while power for the integrated circuit 418 is provided by the RF power supply 412, an RF boost module 420 is provided with the integrated circuit 418. As described above, the RF enhancement module 420 may include one or more capacitors (not shown), for example, one or more capacitors connected in parallel. One or more capacitors may be connected to the integrated circuit 418 to store energy harvested from, for example, the RF power source 412, and configured to provide energy to the integrated circuit 418 to enhance the return signal back to the RFID reader (not shown).

In addition to the above disadvantages, the smaller tag antenna aperture will inherently become narrowband. Accordingly, RFID tags incorporating such tag antennas may be limited to a particular geographic area or range. Thus, RFID tags operating in the united states, uk, china and/or japan may all require unique antenna designs to operate within a specified geographic area. There may not be a problem if RFID tags are deployed in only one specific area, but for international applications this will result in an increase in Stock Keeping Units (SKUs) that the RFID converters and their customers must manage in their supply chain. For example, brands and retailers that sell products internationally will require different RFID tags for a given product sold in the united states and the same product sold in europe. This requirement reduces the efficiency of the supply chain and increases the cost that may ultimately be passed on to the consumer.

To address this issue, some embodiments of the present disclosure have switchable or variable impedances within the integrated circuit. By providing switchable impedances, a step change from one geographical band to another geographical band may be created. According to some embodiments, the step change is operated using an RF command from the RFID reader. For example, when an RFID tag is to be deployed in a particular geographic area, a printer or other method of applying the RFID tag to a product may be set to the particular geographic area by RF command at an initial location in the supply chain. As the product circulates throughout the supply chain, if it is to be shipped to an area in the supply chain where the next operation is to an RFID reader with a different operating frequency, the RFID tags may be inventoried and the "geo-location selection" command may switch the tags to the appropriate impedance to provide the operating frequency of the area where the RFID tagged product is to be deployed. Thus, the "geo-select" command may improve the performance of the RFID tag by optimizing for the new geographic area.

According to some embodiments, the RFID chip or integrated circuit may have the capability to change the impedance matching strategy according to preset conditions or adaptive conditions. Generally, two impedance matching strategies may be used between the integrated circuit and the tag antenna. For example, with an integrated circuit resistor R_pAnd an integrated circuit capacitor C_pThe relatively wide frequency band power matching may allow the tag to operate over the entire operating frequency range of the RFID reader. As discussed further below, such tags may operate over a continuous frequency range or two different frequency bands. Generally, as described above, the operating range of an RFID reader is associated with a particular geographic area as well as other factors (e.g., co-location with an interference source). Alternatively, a relatively narrow band matching may be provided, in which the reactive component of the antenna impedance is designed to resonate with the integrated circuit input capacitance. Thus, the high integrated circuit resistance R_pWill have a high Q value and the maximum possible voltage on the integrated circuit.

RFID chips typically contain structures designed to multiply the input alternating current ("AC") voltage from an RF power source before converting the input AC voltage to a direct current ("DC") voltage to power the integrated circuit. These voltage multipliers may contain switches, such as diodes or transistors, and may have a minimum operating voltage. Thus, a higher input voltage may be advantageous to give a lower operating threshold. The input impedance of the integrated circuit may be a function of the energy lost in the item, such as an electrostatic discharge diode, and the power required by the integrated circuit to charge the internal capacitor to allow the RFID tag to operate.

Generally, a high integrated circuit resistance R resulting in a higher input impedance_pAssociated with narrow bandwidth and resonant matching and limited charging rate of the internal capacitors. Because of, for example, a high R_pThe tag of (a) may not generally be able to accept power on multiple frequencies in the frequency band associated with frequency hopping, so it may only be able to operate at one frequency or a very narrow range of frequencies. Thus, the tag must wait for the RF reader system to transmit at the correct frequency before the tag can begin rectifying the power received from the RF power source. Moreover, since it has a high R_pSuch tags may require multiple charging events, which in turn reduces the response speed of the tag, resulting in slower charging of the internal capacitor. However, the high input impedance allows the amplifier circuit to provide good amplification of the input signal. Conversely, a lower R resulting in a lower input impedance_pTypically associated with a wider frequency band conjugate impedance power match, enabling such tags to be used with RFID reader systems that are capable of periodically changing frequency (frequency hopping) and faster charging of internal capacitors. Such a feature may advantageously provide a faster response speed for the integrated circuit and thus for the RFID tag.

Referring to FIG. 5, an integrated circuit 500 for an RFID tag may have a constant capacitance C_pAnd a switchable resistance R_pThereby providing a switchable input impedance. For example, the integrated circuit 500 may switch between a first input impedance and a second input impedance, where the second input impedance is greater than the first input impedance. By providing an integrated circuit that can be switched between a relatively low first input impedance and a relatively high second input impedance, advantages associated with a low input impedance and a high input impedance may be obtained by some embodiments of the present disclosure. In particular, the relatively low first input impedance may allow the integrated circuit to match a wider frequency range from the RFID reader and provideThe faster internal capacitor charging rate, while the relatively higher second input impedance may provide improved input signal amplification for the integrated circuit.

With continued reference to fig. 5, in some embodiments, the first total resistance R may be provided by providing the integrated circuit 500 with_p(1)To provide a first input resistance and may be provided by providing a second total resistance R to the integrated circuit 500_p(2)To provide a second input impedance. To ensure that the second input impedance is greater than the first input impedance, a second total resistance R_p(2)May be greater than the first total resistance R_p(1). One of ordinary skill in the art will appreciate that the variable total resistance may be implemented in a variety of ways. For example, R_p(1)May be of a single second resistor R_p(2)A single first resistor of low resistance. Alternatively, R_p(1)May be provided by two or more resistors connected in parallel to provide a first total resistance less than a second total resistance, wherein the second total resistance R_p(2)May be provided by any one of two or more resistors, either alone or in combination to provide the ratio R_p(1)A subset thereof connected by means of a second, larger total resistance. In some embodiments, R_p(2)May be provided by two or more resistors connected in series to provide a second total resistance greater than the first total resistance, where the first total resistance R_p(1)May be provided by any one of two or more resistors, either individually or in a subset thereof connected in a manner to provide a lower first total resistance.

In some embodiments, the integrated circuit 500 may be configured to provide an additional total resistance, such as a third total resistance, etc., to enable the integrated circuit 500 to switch to, for example, a third input impedance. In some embodiments, the third total resistance may be greater than the first total resistance and/or greater than the second total resistance. In other embodiments, the third total resistance may be less than the first total resistance and/or less than the second total resistance. In further embodiments, the third total resistance may be greater than the first total resistance, but less than the second total resistance.

In some embodiments, an integrated circuit 500 with switchable input impedance created, for example, by providing a switchable total resistance, may be used in an RFID tag that requires power harvesting as discussed elsewhere herein. For example, the integrated circuit 500 with switchable input impedance may be used as the RF enhancement module 320, 420 or in conjunction with the RF enhancement module 320, 420, as discussed further elsewhere herein.

Referring to fig. 6A and 6B, two types of band occupation are shown. For example, fig. 6A shows continuous frequency bands F1-F2, while fig. 6B shows two discrete frequency bands F1-F2 and F3-F4. The RFID reader is configured to operate on a continuous frequency band, such as the frequency band shown in fig. 6A, which is capable of hopping between different frequencies of the frequency band. RFID readers configured to operate in different sub-bands, such as those shown in fig. 6B, are capable of hopping between different frequencies in the two bands F1-F2 and F3-F4, and may also change periodically between sub-bands.

Fig. 7A and 7B illustrate how an RFID tag with a low input impedance and therefore broadband matching capability works. For example, as shown by the lines labeled 700A and 700B, a tag with low input impedance may operate in its range from F1 to F2 or from F1 to F2 and from F3 to F4. Advantageously, an RFID tag with a low input impedance may therefore give a faster response to an RFID reader system. Moreover, such tags may provide matching at frequencies other than F1 to F2 or F1 to F4 to allow for product related shifts.

In contrast, fig. 8A and 8B illustrate how an RFID tag with a high input impedance provides narrow band matching, as indicated by the lines labeled 800A and 800B. Thus, as shown in fig. 8A, the tag bandwidth is less than the entire range of F1 through F2. Similarly, as shown in fig. 8B, the tag bandwidth operates only in the F3-F4 sub-band, which is less than its full range, and therefore, will not work when the reader is in the F1-F2 band.

The optimal setting selection for the RFID tag may vary depending on various input parameters or values stored in memory. For example, the RFID tag may be pre-programmed to initially operate in a resonant mode. In one example, the spacing and pattern of one or more antennas in the RFID printer system may affect the selected pattern. For printers that stop printing and programming RFID tags, a resonance match condition may be used. In some embodiments, the selected first frequency may be the expected operating frequency of the RFID tag in order to provide optimal communication between the RFID printer system and the RFID tag. The RFID reader of the RFID printer system may then hop to other frequencies over a period of time. While this may interrupt communication, at this point the RFID tag may have moved out of view of the RFID printer system. If adjacent tags are also in a resonant matching condition, simple detuned materials can significantly degrade the performance of adjacent tags because their performance can degrade rapidly with loading under narrow band conditions.

In another example, the resonant mode may be used as part of an in-line test system. In such systems, the system may operate under suppressed radiation conditions and thus may not need to comply with local radio frequency regulations. As a result, the RFID reader may be set to the peak response frequency of the RFID tag at the test location. Adjacent tags may be detuned by dielectric or metallic materials and, being in a resonant mode, their sensitivity may be greatly reduced, preventing them from being read simultaneously with the RFID tag under test. After programming or testing, the tag may be programmed to turn the resonant mode on or off, depending on the type of tag (e.g., a broadband tag for items such as hybrid apparel, or a narrowband tag for merchandise such as cosmetics).

The operating mode may also be commanded as part of a reader command, where testing of a particular bit during a select operation may alter the operating state. This may allow the RFID reader to have control. In some applications, the wideband mode (low R) may be used first_p) Inventory is performed and tags read under this condition may be locked into that state either programmatically or by linking to a flag indicating that the tag has successfully been inventoried. Next, the inventory may be switched to a resonant mode to make the response speed slower, but the Q condition higher (high R)_p). In some cases, this may allow for higher performance and capture of residual tags. Thus, can be obtained in the shortest timeResulting in a more successful overall inventory. In particular, most tags can be captured in a wideband, fast mode, while the remaining tags can be captured in a narrowband, slow mode. According to some embodiments, this operation may be achieved by utilizing a tag with an integrated circuit having a switchable input impedance, as described above.

As shown in FIG. 9, the integrated circuit may be capable of determining resonance (high R)_p) Matched or broadband (low R)_p) The matching is relevant and/or desirable. In some embodiments, integrated circuit 900 has a sub-threshold detector circuit capable of operating below the power level required to activate integrated circuit 900. For example, the sub-threshold detector circuit may have low complexity and operate at a relatively low speed. When an RFID reader hops across a frequency band, the sub-threshold detector circuit may emit a series of pulses to be broadband (low R)_p) Mode and resonance (high R)_p) The input is switched between modes and the result is checked. If the amplitude of all pulses at a given time is similar to the amplitude in the resonant mode, the integrated circuit may select the broadband mode and the integrated circuit may remain in that state for a period of time, for example, between 1 second and 10 seconds. According to other embodiments, the integrated circuit may be held in the broadband mode for more than 10 seconds or less than 10 seconds. Advantageously, keeping the integrated circuit in the broadband mode may provide the same performance as the resonant mode, but at a faster communication speed. In some embodiments, if the peak in the resonant mode is much higher than the peak in the broadband mode, integrated circuit 900 may select the resonant mode and remain in that state for a period of time, as described above. For example, the integrated circuit 900 may remain in the resonant mode for less than 1 second, 1 second to 10 seconds, or more than 10 seconds. By selecting the resonant mode, the communication speed of the integrated circuit may be slowed, but the inventory is more likely, as the total power level rises above the tag operating threshold.

Thus, according to some embodiments, having a low R_pWide band state and high R_pNarrow band selectable state integrated circuits having the same, improved two state or adaptive mechanism, in which the capacitance is alsoThe optimization performance (often referred to as auto-tuning or auto-tuning) can be varied and the integrated circuit can be used to optimize the performance of tags of different sizes and applications within RFID printers and in-line testers and inventory and other reading conditions.