Active backscatter integrated circuit for 3GPP / WIFI / BLE ambient IoT application

Abstract

Methods, systems, and devices related to an active backscatter circuit architecture are described. One example embodiment relates to an active backscatter tag that includes at least one radiofrequency (RF) amplifier, a frequency translator, an active re-modulator; a final-stage RF amplifier coupled to the frequency translator, and an output. The disclosed embodiments include techniques to provide modulated signals with reduced energy consumption and improved transmission range.

Description

PCT Application Attorney Docket No. 009062.8544.WOOO ACTIVE BACKSCATTER INTEGRATED CIRCUIT FOR3GPP / WIFI / BLE AMBIENT IOT APPLICATIONCROSS-REFERENCE TO RELATED APPLICATION

[0001] This patent document claims priority to and benefits of U.S. Provisional Application 63 / 754,454, entitled “ACTIVE BACKSCATTER INTEGRATED CIRCUIT FOR FUTURE 3GPP / WIFI / BLE AMBIENT IOT APPLICATION.” and filed on February 5, 2025. The entire content of the above noted patent application is incorporated by reference as part of the disclosure of this patent document.TECHNICAL FIELD

[0002] The present patent document relates to systems, methods, and devices for providing modulated signals with reduced energy consumption and improved transmission range.BRIEF DESCRIPTION OF THE DRAWINGS

[0003] FIG. 1 shows a block diagram of an example active backscattering tag according to an embodiment of the disclosed technology.

[0004] FIG. 2 shows a block diagram of an example modulator according to an embodiment of the disclosed technology.

[0005] FIG. 3 shows a schematic diagram of an example amplifier according to an embodiment of the disclosed technology.

[0006] FIG. 4 shows a schematic of an example multi-stage system based on the disclosed technology.

[0007] FIG. 5 shows a schematic diagram of an example poly-phase filter (PPF) and singlesideband (SSB) mixer according to an embodiment of the disclosed technology.

[0008] FIG. 6 shows an example gain profile of an amplifier according to an embodiment of the disclosed technology.

[0009] FIG. 7 shows an example PCB layout and chip micrograph according to an embodiment of the disclosed technology.-1- 009062.8544.WO00\l 84836539.1PCT Application Attorney Docket No. 009062.8544.WOOO

[0010] FIG. 8 shows a schematic of an example system based on an active backscatter tag according to an embodiment of the disclosed technology.

[0011] FIG. 9 shows a schematic of an example system based on an active backscatter tag according to an embodiment of the disclosed technology.

[0012] FIG. 10 shows a block diagram of an example system according to an embodiment of the disclosed technology.

[0013] FIG. 11 shows a block diagram of an example system according to an embodiment of the disclosed technology.

[0014] FIG. 12 shows a block diagram of an example system that may be incorporated as part of a multi-stage system based on the disclosed technology.

[0015] FIG. 13 shows a block diagram of an example system that may be incorporated as part of a multi-stage system based on the disclosed technology.

[0016] FIG. 14 shows a block diagram of an example system that may be incorporated as part of a multi-stage system based on the disclosed technology.

[0017] FIG. 15 shows an image of an example chip structured to support a multi-stage system based on the disclosed technology.

[0018] FIG. 16 shows a flow chart of an example method according to an embodiment of the disclosed technology.DETAILED DESCRIPTION

[0019] In the framework of ambient Internet of Things (loT) within the 3GPP standards community, there are two types of devices defined in the standards, where Device I may have the lowest achievable power consumption as below 1 micro-watt (pW), while Device II has the energy storage and power consumption in the range of a few hundred pW. In Device I, the downlink operation may be implemented by the energy-efficient passive envelope-detector-based receiver with 1-bit ADC and digital baseband, and the uplink may be implemented with backscatter circuits that use time-varying impedance loads to create proper modulation and reflection. Although Device II consumes more power than Device I, Device II has a greater uplink communication range than Device I by, for example, utilizing traditional transmitters that consume a great amount of power. Existing-2- 009062.8544.WO00\l 84836539.1PCT Application Attorney Docket No. 009062.8544.WOOO technologies use active devices in the backscatter tags to present a negative resistance to the ambient excitation signal, thereby enhancing the read range. For example, the use of a tunnel diode to terminate the tag antenna and operate the tunnel diode in the negative resistance region has been previously reported. The negative resistance increases the tag reflection coefficient to much higher than 1 and reflects an amplified version of the incident signal thus extending the tag range. However, there are some drawbacks of tunnel diode, for example, (i) the tunnel diode works only over a narrow range of frequencies, (ii) it is difficult to obtain the tunnel diode, and (iii) the impedance of the tunnel diode is a function of frequency, biasing, temperature and input signal power, which makes the operation unstable. Some have reported utilizing a reflection amplifier instead of a tunnel diode, which also presents a negative resistance at the amplifier’s output port. For example, some have reported use of bidirectional amplifiers made of couplers and reflection amplifiers to design a retroreflective backscatter tag. However, such reflection amplifiers can quickly go into oscillations if the amplifier bias is not properly adjusted and can no longer amplify the backscattered signals.

[0020] The disclosed embodiments include an active backscatter circuit architecture for Device II that can provide a reduced power consumption and an improved communication range. Some disclosed embodiments may be used under 802.11ax / be standard that uses Orthogonal Frequency-Division Multiplexing (OFDM). Like other WiFi standards, 802.11ax / be uses 20 MHz channels. However, unlike 802.11b, each channel in 802.1 lax / be contains nine 2 MHz RUs, each with 26 subcarriers. In some embodiments, a single RU for backscatter is used to optimize the gain performance. The fundamental challenge with backscattering an OFDM-based system is that transmitted data is embedded in sub-carriers, making it difficult to individually access and modify them on a low-power backscattering tag. Some disclosed embodiments of the active-backscatter circuit may directly modulate all sub-carrier symbol simultaneously, instead of modulating individual OFDM subcarriers.

[0021] Some example applications of the disclosed embodiments may include translating the WiFi Channel 1 (or 11) incident signal to channel 11 (or 1) as a backscatter signal, with the IF of 50 MHz. Instead of suffering from the loss due to the passive manner, some disclosed embodiments include a series of gain blocks in the active backscatter chain to combat the limited link budget. By choosing the lowest guard interval time of 0.8 ps, the effective symbol time in 802.1 lax / be is 12.8ps + 0.8ps = 13.6ps. This translates to a data rate of 73.5 kbps using BPSK backscatter. With QPSK, the data rate doubles to 146 kbps, resulting in a spectral efficiency of 73.5 kbps / MHz. Some disclosed-3- 009062.8544.WO00\l 84836539.1PCT Application Attorney Docket No. 009062.8544.WOOO embodiments modulate either BPSK or QPSK data onto a single 2 MHz RU while simultaneously translating the incident signals to another channel with active gain. To mitigate the self-interference caused by retransmitting signal leakage, some disclosed embodiments include a Q-boosting amplifier with a sharp filter response in the backscatter chain.

[0022] In one aspect, an active backscatter tag for providing modulated signals with reduced energy consumption and improved transmission range is disclosed. In another aspect, a method for providing the modulated signals with reduced energy consumption and improved transmission range is disclosed. In some embodiments, the active backscatter tag modulates Quadrature Phase Shift Keying (QPSK) or Binary Phase-shift Keying (BPSK) data onto a single 2 MHz WiFi-6 Resource Unit (RU) at 2.4GHz band while simultaneously translating the incident signals to another channel with active gain. To mitigate interference caused by retransmitting signal leakage, the active backscatter tag includes an amplifier with a sharp filter response. In some embodiments, the active backscatter tag includes an on-chip RC poly-phase filter (PPF)-based architecture to generate I / Q incident signals. For example, one or more radiofrequency (RF) amplifiers convert a single-ended incident signal to differential signals before they enter the PPF. To prevent amplified signals from leaking back to the incident antenna port, the active backscatter tag includes a channel-wise filter. Both upper-sideband and lower-sideband notches are placed in the one or more RF amplifiers, and Q-boosting techniques are utilized to sharpen the filter’s response. Since Q-boosting is applied outside the band of interest for the one or more RF amplifiers, a minimal noise and linearity impact is achieved. The PPF then transforms differential signals into I / Q incident signals. By mixing these VQ incident signals with I / Q intermediate frequency (IF) signals and summing the outputs of two mixers, a single-sideband (SSB) signal is generated. Passive mixers are utilized to minimize power consumption. The SSB signal is further amplified by a final-stage RF amplifier before transmitted by an output antenna. In some embodiments, the final-stage RF amplifier is an in-band Q-boosting amplifier with filtering.

[0023] In one aspect, an active backscatter tag that has reduced power consumption and improved transmission range is disclosed. An example embodiment of the active backscatter tag comprises two antennas (i.e., an input antenna and an output antenna), and an active backscatter chain in the form of integrated circuits which comprises three stages of RF amplifiers, a frequency translator, and an active re-modulator coupled to the frequency translator. The active backscatter-4- 009062.8544.WO00\l 84836539.1PCT Application Attorney Docket No. 009062.8544.WOOO chain may be designed for OFDM WiFi backscatter. The modulator is configured to target symbollevel backscatter for one RU bandwidth. The active backscatter chain may use the frequency translator to translate the incident WiFi signal from a first frequency band to a second frequency band. For example, the first frequency band is WiFi channel 1, and the second frequency band is WiFi channel 11. As another example, the first frequency band is WiFi channel 11, and the second frequency band is WiFi channel 1. The frequency translator comprises a PPF and an SSB mixer, which provide the functionality of translating the incident signal from the first frequency band to the second frequency band. The active backscatter chain may comprise three stages of RF amplifier. The first-stage and the second-stage RF amplifiers together provide narrow-band band-pass filtering with two tunable notches at 50MHz offset frequency using out-of-band Q-boosting techniques. The third-stage RF amplifier leverages in-band Q-boosting to provide high gain band-pass response. This is provided to prevent interference between the incident signal and the output signal. In some embodiments, the active backscatter chain works below 1 milliwatt (mW) and provides 10-20 dB in-band gain and over 45dB of notch rejection at 50MHz offset, where the gain and rejection are tunable.

[0024] In another aspect, an active backscatter tag is disclosed. The active backscatter tag comprises: at least one radiofrequency (RF) amplifier coupled receive an incident signal in a first frequency band and comprising a first frequency- selective component configured to selectively pass or reject specific frequency components of the incident signal; a frequency translator coupled to the at least one RF amplifier and configured to provide a second signal at a second frequency band based on the two amplified differential signals; an active re-modulator coupled to the frequency translator and configured to encode data on the second signal; a final-stage RF amplifier coupled to the frequency translator and comprising a second frequency- selective component configured to selectively pass or reject specific frequency components of the second signal; and an output antenna coupled to the final-stage RF amplifier and configured to transmit the amplified signal. In some implementations, the at least one RF amplifier is configured to provide two amplified differential signals based on the incident signal after interaction of the incident signal with the first frequency-selective component. In some implementations, the final-stage RF amplifier is configured to provide an amplified signal by amplifying the second signal after interaction of the second signal with the second frequency-selective component.-5- 009062.8544.WO00\l 84836539.1PCT Application Attorney Docket No. 009062.8544.WOOO

[0025] Tn another aspect, a method of data communication is disclosed. The method comprising: receiving, by at least one radiofrequency (RF) amplifier, an incident signal in a first frequency band; after interaction of the incident signal with the first frequency- selective component; generating two amplified differential signals based on the incident signal by operating the at least one RF amplifier; generating a second signal at a second frequency band based on the two amplified differential signals by operating a frequency translator coupled to the at least one RF amplifier; encoding data on the second signal by operating an active re-modulator coupled to the frequency translator; generating an amplified signal by operating a final-stage RF amplifier coupled to the frequency translator and comprising a second frequency-selective component configured to selectively pass or reject specific frequency components of the second signal; and transmitting the amplified signal to an output antenna coupled to the final-stage RF amplifier. In some implementations, the at least one RF amplifier comprises a first frequency-selective component configured to selectively pass or reject specific frequency components of the incident signal. In some implementations, the amplified signal is generated by amplifying the second signal after interaction of the second signal with the second frequency- selective component

[0026] The disclosed embodiments may open a new direction for the 3GPP ambient loT Device II that enables long-range backscatter operation and may work well for WiFi-to-WiFi backscatter and tone-to-WiFi backscatter applications. Demonstrations have shown that, with 1 mW power consumption, the disclosed scheme can be implemented with today’s semiconductor technology to provide a reasonable bandwidth of at least few hundred kilobits per second (e.g.. 2 to 100 Kbps) at a transmission distance of up to 40 meters.

[0027] FIG. 1 shows an example block diagram of an active backscatter tag according to an embodiment of the disclosed technology. FIG. 2 shows an example block diagram of a modulator that can be implemented with the active backscattering tag of FIG. 1. FIG. 3 shows an example schematic diagram of an RF amplifier (e.g., third stage amplifier) that can be implemented with the active backscattering tag and modulator of FIGS. 1 and 2.

[0028] As shown in FIG. 1, an incident signal first, after receipt by an input antenna, passes through at least one amplifier with two notches, and then through the PPF to generate I / Q signals. An SSB mixer, controlled by the modulated IF control signal, is used to generate the SSB signal at the output of the mixer. The modulated IF control signal is generated by choosing quadrature IF based-6- 009062.8544.WO00\l 84836539.1PCT Application Attorney Docket No. 009062.8544.WOOO on the baseband data, as shown in FIG. 2. This signal is then amplified by a final stage amplifier (e.g., a third-stage RF amplifier) with a Q-boosted band-pass response to achieve sharp gain, as shown in FIG. 3. Finally, the signal is buffered and transformed into a single-ended 50-ohm condition using an off-chip balun.

[0029] In an example embodiment, the active backscatter tag includes a channel-wise filter to prevent amplified retransmitting signals from leaking back to the incident antenna port. Both uppersideband and lower-sideband notches may be placed in the amplifier (for example, a first stage amplifier includes a lower-side notch, and a second stage amplifier includes a higher-side notch), and Q-boosting techniques are utilized at the notches to sharpen the filter’s response. Since Q-boosting is applied outside the band of interest, a minimal noise and linearity impact is achieved.

[0030] FIG. 4 shows a schematic of an example multi-stage system based on the disclosed technology. FIG. 4 (left) shows a block diagram of an example system that may be incorporated as part of a first stage of the multi-stage system. FIG. 4 (right) shows a block diagram of an example system that may be incorporated as part of a second stage of the multi-stage system.

[0031] As shown in FIG. 4 (left), the first stage amplifier system includes an off-chip stepdown transformer to reduce power consumption. To create a lower-side notch, a capacitively coupled LC resonator is added at the node between the main device and the cascade device, creating a zero slightly below the resonance frequency and shorting the signal to AC ground at the notch frequency. A single-ended Q-boosting circuit is added to sharpen the filter shape, with the sharpness and amount of rejection adjustable via the Q-boosting current mirror.

[0032] As shown in FIG. 4 (right), the second stage amplifier system includes a higher-side notch, and splits the first stage output into two signal paths: one with a flat frequency response and the other with a Q-boosted band-pass response at the notch frequency. By subtracting these two signals, a differential signal is created, generating a higher-side notch simultaneously. The sharpness of the filter can be adjusted by tuning the gain of the band-pass path and the amount of Q-boosting current. Although these notches can be tunable, the rejection performance decreases as the notches are placed closer to the center frequency (for example if 25MHz IF is intended).

[0033] In an example embodiment, a frequency translation between WiFi Ch. 1 and Ch. 11 is achieved based on SSB mixing. FIG. 5 shows a schematic diagram of an example PPF and SSB mixer-7- 009062.8544.WO00\l 84836539.1PCT Application Attorney Docket No. 009062.8544.WOOO according to an embodiment of the disclosed technology. As shown in FIG. 5, an on-chip RC PPF-based architecture is included to generate I / Q incident signals, the single-ended incident signal is converted to differential signals using the second- stage amplifier before it enters the PPF. The PPF then transforms the differential signals into I / Q signals. By mixing these I / Q signals with I / Q IF signals and summing the outputs of two mixers, an SSB signal is generated. Passive mixers are utilized to minimize power consumption. Because the RC PPF is fully on-chip, it avoids the variations associated with off-chip components and interconnection parasitic, which are present in existing passive SSB backscatter designs that use off-chip inductors for quadrature loads. Simulation results demonstrate that the disclosed approach can achieve up to 20 dB better single-sideband rejection compared to existing passive backscatter methods that depend on the precision of off-chip inductors. The active backscatter tag may include a first-order passive PPF, which covers the whole 2.4 GHz band and consumes close to zero power while providing an image rejection ratio (IRR) of over 20 dB, even with a 10% resistor variation.

[0034] FIG. 6 shows an example gain performance of an amplifier based on the disclosed technology. As shown in FIG. 6. results in the 65 nm CMOS process indicate over 45 dB SSB rejection at the retransmitting frequency, and 10 to 20 dB in-band gain. The gain and rejection performance can be adjusted based on power consumption and bandwidth requirements. For example, the notch frequency is tunable. In the example of FIG. 6, the total power consumption is below 1 mW including the output buffer. The power consumption is tunable but may have a trade-off between the gain and rejection performance. The results of FIG. 6 demonstrate that the disclosed embodiments can break the range limitation of passive backscatter while maintaining sub-mW power consumption, significantly lower than conventional WiFi systems, which typically consume tens to hundreds of mW.

[0035] FIG. 7 shows a schematic of an example three-dimensional PCB layout and 1 mm by 1 mm chip micrograph according to an embodiment of the disclosed technology.

[0036] FIG. 8 (center) shows a schematic of an example system based on an active backscatter tag according to an embodiment of the disclosed technology. In comparison to existing technologies such as a WiFi transmitter (TX) (shown FIG. 8, left) and passive backscatter tag (shown FIG. 8, right), some implementations of the disclosed system can provide a longer range with a modest amount of power (e.g., 1 mW). As shown in FIGS. 8 and 9, the active backscatter tag can be configured to-8- 009062.8544.WO00\l 84836539.1PCT Application Attorney Docket No. 009062.8544.WOOO communicate with a transmitter (TX) and / or a receiver (RX) to send and receive data. Tn some embodiments, the tag can be implemented with an TOT sensor and a gain amplifier (FIGS. 8 and 9). In an example implementation of the system, the tag notches out the interference signal, modulates data onto the desired signal, translates the signal to another channel, and amplifies it (e.g., gain = 10-20 dB). In some implementations, the system can be operated at a power level less than 1 mW. In an example implementation, the following parameters may be used: Incident: WiFi llax / be (one RU); Backscatter: WiFi llax / be (one RU); Symbol-level BPSK7QPSK modulation for all OFFM subcarriers: SSB channel translation: Ch. 1 to 11 or vice versa. Among other features and benefits, the system shown in FIG. 8 (center) and FIG. 9 sits in between passive backscatter and active transmission.

[0037] FIG. 10 shows a block diagram of an example system according to an embodiment of the disclosed technology. As shown in FIG. 10. the system can include multiple amplifiers operable according to stages (e.g., first stage amplifier, second stage amplifier, and third stage amplifier) and various components / devices such as a matching network, PPF, SSB mixer, and PLL. In some embodiments, the PLL is coupled to a crystal reference as shown in FIG. 10. In some embodiments, the first stage amplifier, second stage amplifier, third stage amplifier, PPF, SSB mixer, and PLL are structured on a chip (represented by dotted rectangle in FIG. 10), such as that shown in FIG. 7 or FIG.15. In some implementations, some or all of the matching network, one or more antennas, crystal reference, balun, and the output antenna are located off-chip.

[0038] FIG. 11 shows a block diagram of an example system according to an embodiment of the disclosed technology. The top left graph in FIG. 11 shows an example of an input signal that can be received at an input antenna coupled to the system. The top right graph in FIG. 11 shows an example of an output signal that can be transmitted by an output antenna coupled to the system.

[0039] FIG. 12 shows a block diagram of an example amplifier according to an embodiment of the disclosed technology. The amplifier may be a first stage amplifier included as part of a multi-stage system based on the disclosed technology. In some embodiments, some or all of the components inside of the dotted rectangle in FIG. 12 may be structured on a chip, such as that shown in FIG. 7 or FIG. 15. FIG. 12 also shows an example circuit diagram of a C-coupled LC resonator that may be included in the multi-stage system and exemplary reactance versus frequency data that can be achieved in accordance with some implementations of the system.-9- 009062.8544.WO00\l 84836539.1PCT Application Attorney Docket No. 009062.8544.WOOO

[0040] FIG. 13 shows a block diagram of an example amplifier according to an embodiment of the disclosed technology. The amplifier may be a second stage amplifier included as part of a multistage system based on the disclosed technology. In some embodiments, some or all of the components inside of the dotted rectangle in FIG. 13 may be structured on a chip, such as that shown in FIG. 7 or FIG. 15. In some embodiments, the amplifier shown in FIG. 13 and the amplifier shown in FIG. 12 are coupled to form a multi-stage amplification system. FIG. 13 also shows a plot of an example gain performance that can be achieved in accordance with some implementations of the system.

[0041] FIG. 14 shows a block diagram of an example amplifier according to an embodiment of the disclosed technology. The amplifier may be a third stage amplifier included as part of a multistage system based on the disclosed technology. In some embodiments, the third stage amplifier of FIG.14, the second stage amplifier of FIG. 13, and the first stage amplifier of FIG. 12 are coupled to form a multi-stage amplification system. Among other features and benefits, the amplifier in FIG. 13 may provide a resonance tank at output frequency and in-band Q-boosting offering less noise penalty and high gain.

[0042] FIG. 15 shows an image of an example chip structured to support a multi-stage system based on the disclosed technology. As shown in FIG. 15, the chip is structured to support a first stage amplifier, second stage amplifier, third stage amplifier, PPF, mixer, modulator, buffer, and various additional circuit elements. In some embodiments, the chip has dimensions 1 x 1 mm (length x width).

[0043] FIG. 16 shows a flow chart of an example method of data communication according to an embodiment of the disclosed technology. At step 1610, the method 1600 includes receiving, by at least one radiofrequency (RF) amplifier, an incident signal in a first frequency band, wherein the at least one RF amplifier comprises a first frequency- selective component configured to selectively pass or reject specific frequency components of the incident signal. At step 1620, the method 1600 includes after interaction of the incident signal with the first frequency- selective component, generating two amplified differential signals based on the incident signal by operating the at least one RF amplifier. At step 1630, the method 1600 includes generating a second signal at a second frequency band based on the two amplified differential signals by operating a frequency translator coupled to the at least one RF amplifier. At step 1640, the method 1600 includes encoding data on the second signal by operating an active re-modulator coupled to the frequency translator. At step 1650, the method 1600 includes generating an amplified signal by operating a final-stage RF amplifier coupled to the-10- 009062.8544.WO00\l 84836539.1PCT Application Attorney Docket No. 009062.8544.WOOO frequency translator and comprising a second frequency-selective component configured to selectively pass or reject specific frequency components of the second signal, wherein the amplified signal is generated by amplifying the second signal after interaction of the second signal with the second frequency- selective component. At step 1660, the method 1600 includes transmitting the amplified signal to an output antenna coupled to the final- stage RF amplifier.

[0044] In one aspect, a method of data communication with reduced energy consumption and improved transmission range is disclosed. An example implementation of the method is next described. An input antenna receives an incident signal at a first frequency band. At least one RF amplifier provides two amplified differential signals based on the incident signal. A frequency translator provides a second signal at a second frequency band based on the two amplified differential signals. An active re-modulator encodes data on the second signal. A final-stage RF amplifier provides an amplified signal by amplifying the second signal. An output antenna transmits the amplified signal.

[0045] Another example implementation of the method is next described. An incident signal in a first frequency band is received at a first stage. A transmission signal in a second frequency band is generated by operating an active re-modulator on an output of the first stage, where the active remodulator is powered by a power source. The active re-modulator is configured to provide a signal gain from the incident signal to the transmission signal. In some embodiments, the transmission signal is generated by amplifying a modulated signal in the second frequency band that is generated based on the output of the first stage.

[0046] Embodiments of the disclosed technology support inter alia the following technical solutions.

[0047] 1. An active backscatter tag, comprising: at least one radiofrequency (RF) amplifier coupled receive an incident signal in a first frequency band and comprising a first frequency-selective component configured to selectively pass or reject specific frequency components of the incident signal, wherein the at least one RF amplifier is configured to provide two amplified differential signals based on the incident signal after interaction of the incident signal with the first frequency- selective component; a frequency translator coupled to the at least one RF amplifier and configured to provide a second signal at a second frequency band based on the two amplified differential signals; an active re-modulator coupled to the frequency translator and configured to encode data on the second signal;-11- 009062.8544.WO00\l 84836539.1PCT Application Attorney Docket No. 009062.8544.WOOO a final-stage RF amplifier coupled to the frequency translator and comprising a second frequency-selective component configured to selectively pass or reject specific frequency components of the second signal, wherein the final-stage RF amplifier is configured to provide an amplified signal by amplifying the second signal after interaction of the second signal with the second frequency-selective component; and an output antenna coupled to the final- stage RF amplifier and configured to transmit the amplified signal.

[0048] 2. The active backscatter tag of solution 1, wherein the second frequency band does not overlap with the first frequency band.

[0049] 3. The active backscatter tag of solution 2, wherein the first frequency band is WiFi channel 1 and the second frequency band is WiFi channel 11.

[0050] 4. The active backscatter tag of solution 2, wherein the first frequency band is WiFi channel 11, and the second frequency band is WiFi channel 1.

[0051] 5. The active backscatter tag of solution 1, wherein the at least one RF amplifier comprises a first-stage amplifier having a lower-side notch, and a second-stage amplifier having a higher- side notch.

[0052] 6. The active backscatter tag of solution 1, wherein the frequency translator comprises a poly-phase filter (PPF) coupled to the at least one RF amplifier and two single sideband (SSB) mixers coupled to the PPF.

[0053] 7. The active backscatter tag of claim 6, wherein each of the two SSB mixers is a passive mixer configured to generate an SSB signal, wherein the final-stage RF amplifier is configured to amplify an output SSB signal that is a summation of the SSB signal generated by each of the two SSB mixers.

[0054] 8. The active backscatter tag of solution 1, wherein the active re-modulator comprises a phase-locked loop (PLL), and wherein the active re-modulator is configured to modulate the second signal by switching between four phases of intermediate frequency (IF) clocks using an SSB modulator coupled to the frequency translator.-12- 009062.8544.WO00\l 84836539.1PCT Application Attorney Docket No. 009062.8544.WOOO

[0055] 9. The active backscatter tag of solution 8, wherein the active re-modulator is further configured to encode the data on the second signal by performing Binary Phase- Shift Keying (BPSK) or Quadrature Phase-Shift Keying (QPSK) modulation on the second signal.

[0056] 10. The active backscatter tag of solution 1, wherein the active backscatter tag is operable below 1 milliwatt (mW).

[0057] 11. The active backscatter tag of solution 1, wherein the final- stage RF amplifier is an in-band Q-boosting amplifier with filtering.

[0058] 12. The active backscatter tag of solution 1, comprising an input antenna configured to receive the incident signal in the first frequency band and to provide the incident signal to the at least one RF amplifier.

[0059] 13. The active backscatter tag of solution 1, wherein the active backscatter tag is configured to provide a bandwidth between 2 to 100 Kps.

[0060] 14. The active backscatter tag of solution 1, wherein at least one of the first frequency-selective component and the second frequency- selective component comprises an isolator, a circulator, a filter, or a passive device.

[0061] 15. A method of data communication, comprising: receiving, by at least one radiofrequency (RF) amplifier, an incident signal in a first frequency band, wherein the at least one RF amplifier comprises a first frequency-selective component configured to selectively pass or reject specific frequency components of the incident signal: after interaction of the incident signal with the first frequency-selective component, generating two amplified differential signals based on the incident signal by operating the at least one RF amplifier; generating a second signal at a second frequency band based on the two amplified differential signals by operating a frequency translator coupled to the at least one RF amplifier; encoding data on the second signal by operating an active re-modulator coupled to the frequency translator; generating an amplified signal by operating a finalstage RF amplifier coupled to the frequency translator and comprising a second frequency- selective component configured to selectively pass or reject specific frequency components of the second signal, wherein the amplified signal is generated by amplifying the second signal after interaction of the second signal with the second frequency- selective component; and transmitting the amplified signal to an output antenna coupled to the final-stage RF amplifier.-13- 009062.8544.WO00\l 84836539.1PCT Application Attorney Docket No. 009062.8544.WOOO

[0062] 16. The method of solution 15, wherein the second frequency band does not overlap with the first frequency band.

[0063] 17. The method of solution 15, wherein the frequency translator comprises a poly-phase filter (PPF) coupled to the at least one RF amplifier and two single sideband (SSB) mixers coupled to the PPF.

[0064] 18. The method of solution 15, wherein the active re-modulator comprises a phase-locked loop (PLL), and wherein the active re-modulator is configured to modulate the second signal by switching between four phases of intermediate frequency (IF) clocks using an SSB modulator coupled to the frequency translator.

[0065] 19. The method of solution 15, wherein the final-stage RF amplifier is an in-band Q-boosting amplifier with filtering.

[0066] 20. The method of solution 15. wherein at least one of the first frequency- selective component and the second frequency- selective component comprises an isolator, a circulator, a filter, or a passive device.

[0067] 21. An active backscatter tag, comprising: an input antenna configured to receive an incident signal at a first frequency band; at least one radiofrequency (RF) amplifier coupled to the input antenna and configured to provide two amplified differential signals based on the incident signal; a frequency translator coupled to the at least one RF amplifier and configured to provide a second signal at a second frequency band based on the two amplified differential signals; a backscatter modulator coupled to the frequency translator and configured to encode data on the second signal; a final- stage RF amplifier coupled to the frequency translator and configured to provide an amplified signal by amplifying the second signal; and an output antenna coupled to the final-stage RF amplifier and configured to transmit the amplified signal.

[0068] 22. The active backscatter tag of solution 21, wherein the second frequency band does not overlap with the first frequency band.

[0069] 23. The active backscatter tag of solution 22, wherein the first frequency band is WiFi channel 1 and the second frequency band is WiFi channel 11.-14- 009062.8544.WO00\l 84836539.1PCT Application Attorney Docket No. 009062.8544.WOOO

[0070] 24. The active backscatter tag of solution 22, wherein the first frequency band is WiFi channel 11, and the second frequency band is WiFi channel 1.

[0071] 25. The active backscatter tag of solution 21, wherein the at least one RF amplifier comprises a first-stage amplifier having a lower-side notch, and a second-stage amplifier having a higher-side notch.

[0072] 26. The active backscatter tag of solution 21, wherein the frequency translator comprises a poly-phase filter (PPF) coupled to the at least one RF amplifier and two single sideband (SSB) mixers coupled to the PPF.

[0073] 27. The active backscatter tag of solution 21, wherein the backscatter modulator comprises a phase-locked loop (PLL), and wherein the backscatter modulator is configured to modulate the second signal by switching between four phases of intermediate frequency (IF) clocks using an SSB modulator coupled to the frequency translator.

[0074] 28. The active backscatter tag of solution 27, wherein the backscatter modulator is further configured to encode the data at the second signal by performing Binary Phase-Shift Keying (BPSK) or Quadrature Phase-Shift Keying (QPSK) modulation on the second signal.

[0075] 29. The active backscatter tag of solution 21 , wherein the active backscatter tag works below 1 milliwatt (mW).

[0076] 30. The active backscatter tag of solution 21, wherein the final-stage RF amplifier is an in-band Q-boosting amplifier with filtering.

[0077] 31. A method of data communication, comprising: receiving, at a first stage, an incident signal in a first frequency band; and generating a transmission signal in a second frequency band by operating an active backscatter modulator on an output of the first stage, wherein the active backscatter modulator is powered by a power source, and wherein the active backscatter modulator is configured to provide a signal gain from the incident signal to the transmission signal.

[0078] 32. The method of solution 31, wherein the generating the transmission signal in the second frequency band comprises: generating a modulated signal in the second frequency band based on the output of the first stage; and generating the transmission signal by amplifying the modulated signal.-15- 009062.8544.WO00\l 84836539.1PCT Application Attorney Docket No. 009062.8544.WOOO

[0079] Implementations of the subject matter and the functional operations described in this patent document can be implemented in various systems, digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. Implementations of the subject matter described in this specification can be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a tangible and non-transitory computer readable medium for execution by, or to control the operation of, data processing apparatus. The computer readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a composition of matter effecting a machine-readable propagated signal, or a combination of one or more of them. The term “data processing unit” or “data processing apparatus” encompasses all apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, or multiple processors or computers. The apparatus can include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g.. code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them.

[0080] A computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, sub programs, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network.

[0081] The processes and logic flows described in this specification can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be performed by, and apparatus can also be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).-16- 009062.8544.WO00\l 84836539.1PCT Application Attorney Docket No. 009062.8544.WOOO

[0082] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read only memory or a random access memory or both. The essential elements of a computer are a processor for performing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto optical disks, or optical disks. However, a computer need not have such devices. Computer readable media suitable for storing computer program instructions and data include all forms of nonvolatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices. The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry.

[0083] While this patent document contains many specifics, these should not be construed as limitations on the scope of any invention or of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular inventions. Certain features that are described in this patent document in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

[0084] Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Moreover, the separation of various system components in the embodiments described in this patent document should not be understood as requiring such separation in all embodiments.

[0085] Only a few implementations and examples are described and other implementations, enhancements and variations can be made based on what is described and illustrated in this patent document.-17- 009062.8544.WO00\l 84836539.1

Claims

PCT Application Attorney Docket No. 009062.8544.WOOO CLAIMSWhat is claimed:

1. An active backscatter tag, comprising:at least one radiofrequency (RF) amplifier coupled to receive an incident signal in a first frequency band and comprising a first frequency- selective component configured to selectively pass or reject specific frequency components of the incident signal, wherein the at least one RF amplifier is configured to provide two amplified differential signals based on the incident signal after interaction of the incident signal with the first frequency-selective component;a frequency translator coupled to the at least one RF amplifier and configured to provide a second signal at a second frequency band based on the two amplified differential signals;an active re-modulator coupled to the frequency translator and configured to encode data on the second signal;a final-stage RF amplifier coupled to the frequency translator and comprising a second frequency- selective component configured to selectively pass or reject specific frequency components of the second signal, wherein the final-stage RF amplifier is configured to provide an amplified signal by amplifying the second signal after interaction of the second signal with the second frequency- selective component; andan output antenna coupled to the final-stage RF amplifier and configured to transmit the amplified signal.

2. The active backscatter tag of claim 1, wherein the second frequency band does not overlap with the first frequency band.

3. The active backscatter tag of claim 2, wherein the first frequency band is WiFi channel 1 and the second frequency band is WiFi channel 11.

4. The active backscatter tag of claim 2, wherein the first frequency band is WiFi channel 11, and the second frequency band is WiFi channel 1.-18- 009062.8544.WO00\l 84836539.1PCT Application Attorney Docket No. 009062.8544.WOOO 5. The active backscatter tag of claim 1 , wherein the at least one RF amplifier comprises a first-stage amplifier having a lower-side notch, and a second-stage amplifier having a higher-side notch.

6. The active backscatter tag of claim 1, wherein the frequency translator comprises a poly-phase filter (PPF) coupled to the at least one RF amplifier and two single sideband (SSB) mixers coupled to the PPF.

7. The active backscatter tag of claim 6, wherein each of the two SSB mixers is a passive mixer configured to generate an SSB signal, wherein the final-stage RF amplifier is configured to amplify an output SSB signal that is a summation of the SSB signal generated by each of the two SSB mixers.

8. The active backscatter tag of claim 1, wherein the active re-modulator comprises a phase-locked loop (PLL), and wherein the active re-modulator is configured to modulate the second signal by switching between four phases of intermediate frequency (IF) clocks using an SSB modulator coupled to the frequency translator.

9. The active backscatter tag of claim 8, wherein the active re-modulator is further configured to encode the data on the second signal by performing Binary Phase-Shift Keying (BPSK) or Quadrature Phase-Shift Keying (QPSK) modulation on the second signal.

10. The active backscatter tag of claim 1, wherein the active backscatter tag is operable below 1 milliwatt (mW).

11. The active backscatter tag of claim 1, wherein the final-stage RF amplifier is an in-band Q-boosting amplifier with filtering.

12. The active backscatter tag of claim 1, comprising an input antenna configured to receive the incident signal in the first frequency band and to provide the incident signal to the at least one RF amplifier.-19- 009062.8544.WO00\l 84836539.1PCT Application Attorney Docket No. 009062.8544.WOOO 13. The active backscatter tag of claim 1, wherein the active backscatter tag is configured to provide a bandwidth between 2 to 100 Kps.

14. The active backscatter tag of claim 1, wherein at least one of the first frequency-selective component and the second frequency- selective component comprises an isolator, a circulator, a filter, or a passive device.

15. A method of data communication, comprising:receiving, by at least one radiofrequency (RF) amplifier, an incident signal in a first frequency band, wherein the at least one RF amplifier comprises a first frequency-selective component configured to selectively pass or reject specific frequency components of the incident signal;after interaction of the incident signal with the first frequency-selective component, generating two amplified differential signals based on the incident signal by operating the at least one RF amplifier:generating a second signal at a second frequency band based on the two amplified differential signals by operating a frequency translator coupled to the at least one RF amplifier;encoding data on the second signal by operating an active re-modulator coupled to the frequency translator;generating an amplified signal by operating a final-stage RF amplifier coupled to the frequency translator and comprising a second frequency-selective component configured to selectively pass or reject specific frequency components of the second signal, wherein the amplified signal is generated by amplifying the second signal after interaction of the second signal with the second frequency- selective component; andtransmitting the amplified signal to an output antenna coupled to the final- stage RF amplifier.

16. The method of claim 15, wherein the second frequency band does not overlap with the first frequency band.

17. The method of claim 15, wherein the frequency translator comprises a poly-phase filter (PPF) coupled to the at least one RF amplifier and two single sideband (SSB) mixers coupled to the PPF.-20- 009062.8544.WO00\l 84836539.1PCT Application Attorney Docket No. 009062.8544.WOOO 18. The method of claim 15, wherein the active re-modulator comprises a phase-locked loop (PLL), and wherein the active re-modulator is configured to modulate the second signal by switching between four phases of intermediate frequency (IF) clocks using an SSB modulator coupled to the frequency translator.

19. The method of claim 15, wherein the final-stage RF amplifier is an in-band Q-boosting amplifier with filtering.

20. The method of claim 15, wherein at least one of the first frequency- selective component and the second frequency- selective component comprises an isolator, a circulator, a filter, or a passive device.-21- 009062.8544.WO00\l 84836539.1

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