Battery-free wireless general sensor interface platform

Abstract

In some embodiments, there is provided an apparatus comprising a sensor configured to provide a value that varies based on a stimulus at the sensor; at least one radio frequency transceiver circuitry coupled to the sensor, wherein the at least one radio frequency transceiver circuity generates a first radio frequency signal and a second radio frequency signal, wherein the variation in the value modulates a phase and / or an amplitude of the second radio frequency signal generated by the at least one radio frequency transceiver circuitry; and an antenna configured to transmit the modulated second radio frequency signal and the first radio frequency signal. Related systems, methods, and articles of manufacture are also disclosed.

Description

Via Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564 BATTERY-FREE WIRELESS GENERAL SENSOR INTERFACE PLATFORM STATEMENT OF GOVERNMENT SUPPORT

[0001] This invention was made with government support under 1935329 awarded by the National Science Foundation. The government has certain rights in the invention. CROSS-REFERENCE TO RELATED APPLICATION

[0002] This application claims the benefit of U.S. Patent Application 63 / 696,747, titled “BATTERY-FREE wireless GENERAL SENSOR INTERFACE PLATFORM,” which is incorporated herein in its entirety. BACKGROUND

[0003] Sensing technologies may be considered an important part of our digital future and bridge the gap between the real and digital worlds by enabling the digital world to better actuate the real world. For example, sensors may be used to take real-world stimuli (e.g., temperature, moisture, light, and / or other things) and transduce the stimuli into digitized sensor values, which quantifies sensed levels of the stimuli. These digitized sensor values may be communicated to, for example, a central node that can trigger or perform an action. In the case of a heating ventilation air conditioning (HVAC) system for example, the HVAC system may use temperature sensors to better moderate the indoor climate before taking an action. Similarly, farmers may analyze readings reported by soil moisture sensors to optimize irrigation. Sensor technologies may also be used to detect contact forces to record user-interactions, detect or identify contaminants, and / or the like. SUMMARY

[0004] In some example embodiments, there may be provided systems, methods, and articles of manufacture for an RFID-assisted sensing platform. In some embodiments, there is provided an apparatus comprising a sensor configured to provide a value that varies based on a stimulus at the sensor; at least one radio frequency transceiver circuitry coupled to the sensor, wherein the at least one radio frequency transceiver circuity generates a first radio frequencyVia Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564 signal and a second radio frequency signal, wherein the variation in the value modulates a phase and / or an amplitude of the second radio frequency signal generated by the at least one radio frequency transceiver circuitry; and an antenna configured to transmit the modulated second radio frequency signal and the first radio frequency signal.

[0005] One or more of the features disclosed herein or listed below may be included. For example, the at least one radio frequency transceiver circuitry includes a first radio frequency transceiver circuitry and a second radio frequency transceiver circuitry, wherein the second radio frequency transceiver circuitry is coupled to the sensor and generates the modulated second radio frequency signal. The first radio frequency transceiver circuitry is isolated from the second radio frequency transceiver circuitry and the sensor. The at least one radio frequency transceiver circuitry includes a first radio frequency transceiver circuitry coupled to a switch, wherein the switch in a first position provides the first radio frequency signal toward the antenna, and the switch in a second position provides the modulated second radio frequency signal toward the antenna. The at least one radio frequency transceiver circuitry includes radio frequency identification (RFID) circuity. The at least one radio frequency transceiver circuitry comprises passive circuitry. The at least one radio frequency transceiver circuitry includes active circuitry. The apparatus may further include a combiner and / or a switch coupled to the at least one radio frequency transceiver circuitry, wherein the combiner and / or the switch isolates the sensor from the first radio frequency signal. The combiner includes a Wilkinson power combiner, and / or wherein the combiner and / or the switch is further coupled to the antenna. A differential between the modulated second radio frequency signal and the first radio frequency signal may be used to communicate information indicative of the value that varies at the sensor. The modulated second radio frequency signal and the first radio frequency signal are transmitted in response to an electromagnetic signal. The electromagnetic signal is received from a reader, and / or wherein the modulated second radio frequency signal and the first radio frequency signal are transmitted toward the reader. The reader includes a radio frequency identification reader. The sensor is configured with a resonant frequency that is adjusted to a radio frequency within a communication band. The communication band may be a radio frequency identification communication band.

[0006] In some example embodiments, there may be provided an apparatus comprising transceiver circuitry configured to transmit a probe radio frequency signal to a remote apparatusVia Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564 and to receive a responsive radio frequency signal carrying a modulated second radio frequency signal and a first radio frequency signal; and decoding circuitry configured to decode the responsive radio frequency signal based on a difference between the first radio frequency signal and the modulated second radio frequency signal, wherein the difference indicates a value that varies based on a stimulus at a sensor at the remote apparatus.

[0007] One or more of the features disclosed herein or listed below may be included. For example, the remote apparatus includes the apparatus of claim 1. The decoding circuitry is configured to decode using two channels comprising the modulated second radio frequency and the first radio frequency signal. The decoding includes aligning the two channels. The apparatus includes a radio frequency identification reader.

[0008] In some embodiments, there is provided a method including receiving, by at least one radio frequency transceiver circuitry coupled to a sensor, an electromagnetic signal, wherein the sensor is configured to provide a value that varies based on a stimulus at the sensor, wherein the variation in the value modulates a phase and / or an amplitude of a second radio frequency signal generated by the at least one radio frequency transceiver circuitry; and in response an electromagnetic signal, transmitting a first radio frequency signal and the modulated second radio frequency signal, wherein the first radio frequency signal serves as a reference to enable decoding, based on a difference between first radio frequency signal and the modulated second radio frequency signal, information indicative of the value that varies at the sensor.

[0009] In some embodiments, there is provided a method including transmitting a probe radio frequency signal to a remote apparatus; receiving, in response to the probe radio frequency signal, a responsive radio frequency signal carrying a modulated second radio frequency signal and a first radio frequency signal; and decoding the responsive radio frequency signal based on a difference between the first radio frequency signal and the modulated second radio frequency signal, wherein the difference indicates a value that varies based on a stimulus at a sensor at the remote apparatus.

[0010] The details of one or more variations of the subject matter described herein are set forth in the accompanying drawings and the description below. Other features and advantages of the subject matter described herein will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGSVia Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564

[0011] The accompanying drawings, which are incorporated in and constitute a part of this specification, show certain aspects of the subject matter disclosed herein and, together with the description, help explain some of the principles associated with the disclosed implementations. In the drawings,

[0012] FIG. 1 depicts an example plot of the adjusted resonant frequency of a sensor, in accordance with some embodiments;

[0013] FIG. 2A depicts an example of a system including an RFID reader and a passive RFID tag coupled to a sensor having a resonant frequency tuned to the RFID frequency band, in accordance with some embodiments;

[0014] FIG. 2B depicts an example implementation of the passive RFID tag coupled to the sensor, in accordance with some embodiments;

[0015] FIG. 2C depicts example implementation sensor models, in accordance with some embodiments;

[0016] FIG. 2D depicts an example implementation of an RFID reader coupled to the sensor, in accordance with some embodiments;

[0017] FIG. 3A depicts another example system comprising an RFID reader and two passive RFID tags sharing a common antenna, in accordance with some embodiments;

[0018] FIGs. 3B and 3C depict additional examples of the passive RFID tags sharing a common antenna, in accordance with some embodiments;

[0019] FIG. 4 depicts a sensor characterized in a series configuration or a shunt configuration, in accordance with some embodiments;

[0020] FIG. 5 depicts another example of a system, in accordance with some embodiments; and

[0021] FIGs. 6 and 7 depict an example of a process for adjusting the tag data using time warping, in accordance with some embodiments. DETAILED DESCRIPTION

[0022] Although sensor technologies may support multiple diverse stimulus, existing sensor interfaces using communication technologies, such as Bluetooth Low Energy (BLE), Zigbee, LoRa, and / or the like, can require large form factors due to in part the presence of batteries to power the electronics for sensor readout, communications, and / other sensorVia Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564 operations. This form factor including the need for battery power hinders the widespread adoption of some sensor technologies. To illustrate further, the use of battery powered moisture sensors on a farm can have detrimental effects on the farm’s biochemistry (e.g., the battery can represent a contaminant in the soil).

[0023] To reduce the larger form factor and remove battery dependence, so called “passive” RFID tags may be used with a sensor. RFID enables the creation of identity (e.g., carrying stickers that are paper-like, flexible, and can be read wirelessly). The passive RFID tags (which are passive in the sense they do not have a battery) may be adept at communicating their identifier (ID) but may not be adept at communicating digital data that varies in real-time, so it follows that a conventional, passive RFID tag may not be able to communicate data changes measured (e.g., sensed or detected) by a coupled sensor.

[0024] In some embodiments, there is provided an RFID-based sensor system (also referred to as an RFID-assisted sensing platform) comprising at least one RFID tag and at least one sensor. In some embodiments, the RFID tag is passive in the sense that it does not rely on a battery for power. In some embodiments, the sensor is passive as well. As used herein, passive refers to not using an active power source, such as a battery (e.g., the RFID tag harvests energy from the RF signals it receives from an RFID reader).

[0025] In some embodiments, the RFID-based sensor device provides a direct-to-RF interface for the at least one sensor. For example, the sensor may operate using a fundamental operational frequency, such as one or more resonant frequencies. At these resonant frequencies, the sensors are most sensitive to their respective stimuli. This operational frequency may be tuned (e.g., adjusted) to enable communication via a communication channel, such as within the RFID frequency band (e.g., 902-928 MHz used by RFID systems), so it can be read by an RFID reader. For example, passive biasing components (e.g., capacitor, inductors, and / or the like) may be used to adjust the sensor’s resonant frequencies to a desired RF band, such as the RFID frequency band.

[0026] The tuned sensor’s stimuli may become “maximally” coupled to the passive RFID tag circuitry. In this way, this maximal coupling between the sensor stimuli and the RFID tag may be communicated via the RFID communication band. Moreover, by having two passive RFID tags share a common antenna (e.g., with one passive RFID tag maximally coupled (e.g., using a Wilkinson power combiner or a switch) to the sensor and the other passive RFID tagVia Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564 isolated from the sensor and other tag, the sensor’s stimuli may be robustly communicated and readout at the RFID reader (or, e.g., a processor-based device coupled to the RFID reader) even in for example the presence of wireless channel non-idealities, and movement. For example, the RFID reader may read the changes at the sensor by observing channel differences between the two tags interfaced with the same RFID antenna.

[0001] Although some of the examples refer to RFID-based sensors, other types of devices and sensors may be used as well.

[0027] As noted, a sensor may have a fundamental frequency at which the sensor is most sensitive to changes in the stimulus being detected or measured by the sensor. This frequency may be considered or referred to as a resonant frequency, so it may be periodic over a range of frequencies. At these resonant frequencies, the state of the sensor (which indicates the stimulus being measured) may be communicated reliably and passively (e.g., with minimal power consumption that can be met with energy harvesting of wireless signals as in the case with RFID).

[0028] To illustrate further, a sensor 102, such as a capacitive soil moisture sensor, may have an equivalent RF model as shown at FIG. 1. The amplitude over frequency is plotted at 104A-C. There are resonant frequencies at 106A, 106B, 106C, and 106D, for example. In some embodiments, a resonant frequency 106A of the sensor 102 is adjusted or tuned, such that it resonates within the RFID communication band 110. The sensor is tuned by applying a tuning capacitance, such Ctune112. The tuning capacitance (Ctune112) adjusts the resonant point 106A of the sensor 102 to 116A, such that it is within the RFID band 110 or other communication bands as well. The sensor (configured with an impedance adjustment provided by the capacitance (or inductance) 112 is referred to as the impedance adjusted sensor 150. The impedance adjusted sensor 150 amplitude over frequency is plotted at 114A-C.

[0029] FIG. 2A depicts a system 200 including the impedance adjusted sensor 150 coupled to an RFID transceiver 205 (also referred to as a “tag”), in accordance with some embodiments. FIG. 2B depicts an example of the RFID tag 205, in accordance with some embodiments. FIG. 2C depicts example of models 270A-D for the sensor 150, in accordance with some embodiments.Via Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564

[0030] In the example of FIG. 2A, the RFID reader 210 may query 220A the RFID tag 205 by emitting one or more electromagnetic waves within the RFID frequency band towards the RFID tag 205 (which is coupled to the impedance adjusted sensor 150).

[0031] The RFID tag 205 (which is within the electromagnetic wave field) harvests energy from the reader’s electromagnetic waves to power the RFID tag’s circuitry and transmit back towards the reader 210. In the example of FIG. 2A for example, the RFID responds 220B to the query 220A with information about the tag’s digital ID (e.g., carried by S(t) 222A) and the embedded sensor impedance 222B (which carries as shown in FIG. 1 information regarding changes in the sensor’s readings).

[0032] At FIG. 2A, the impedance-modulated reflection coefficient Γ corresponds to: Γ = ^^^^^^^^^^ ^^^^^^^^^^ (1)wherein Zo is the RFID sensor (tag) impedance (Z), and Zsensor corresponds to: Zsensor = ^^^^^^^(^) ^(^^^^^^(^) (2)wherein Vsensor represents the sensor’s voltage frequency response and Isensor(f) represents the sensor’s current frequency response.

[0033] Referring to FIG. 2B, FIG. 2B depicts an example of the RFID tag 205 (see, also, e.g., RFID transceivers 305 / 307). The device includes two antenna terminals labeled Ant / positive 290A and Ant / negative 290B. These terminals are used to interface the RFID transceiver to an antenna. The device also includes a load-modulation switch 291A connected across the antenna terminals. The switch modulates the tag ID (or other data such as the state or measured or detected stimulus of the sensor) onto a continuous wave transmitted by the RFID reader. The switch 291A also controls switching between impedance states of the transceiver. FIG. 2B also depicts read / write lines 291B / C that correspond to the data moving in and / or out of the RFID transceiver through the antenna terminals. The energy harvester 292 collects energy from a continuous carrier signal transmitted by the RFID reader and powers up the entire transceiver. The memory 294 (e.g., EEPROM flash memory or other type of memory) holds the device’sVia Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564 digital ID, for example. The control module 296 governs read / write operations and houses firmware of the transceiver. For example, the control module may include the EPC Gen2 protocol and collision control operations or other protocols required to communicate with the RFID reader. Read / write 297 operations are also provided for the digital ID of the tag from flash memory.

[0034] Referring to FIG. 2C, it shows various models of the sensor 159 that can be readout using the disclosed system. For example, the model 270A represents a sensor that presents itself as a series RC circuit where R represents equivalent series resistance of the sensor measured at RF, and C represents the capacitance of the sensor that responds to the stimulus being measured. The model 270B represents a shunt RC model. Similarly, the model 270C represents a series RL model where L represents the inductive component of the sensor that shows sensitivity to the stimulus. The model 270D represents the shunt RL model. Thus the sensor 150 may be implemented using a variety of models, such as one of the four models 270A- D which is determined by impedance characterization.

[0035] FIG. 2D depicts an example of an RFID reader 210, in accordance with some embodiments. The RFID reader 210 may include at least one RFID transceiver 280B coupled to at least one antenna 280A. Moreover, the RFID reader may include at least one memory 280D and at least one processor 280C configured to perform one or more operations associated with the RFID reader, such as decoding to provide the sensor value(s), dynamic time warping, and / or the like. Alternatively, or additionally, the RFID reader may include a dedicated circuitry, such as a decoder and / or the like to perform the noted decoding and / or time alignment. Moreover, the RFID reader may include input / output circuitry 280E (for example, to enable coupling to other processors, networks, and / or the like).

[0036] Referring to FIG. 2D for example, the RFID reader may include transceiver circuitry, such as RFID transceiver circuitry 280B (although other RF technologies may be used as well). Moreover, the transceiver may be configured to transmit a probe radio frequency signal to a remote apparatus, such as RF tag(s) 305 and / 307, and in response, receive a responsive radio frequency signal carrying the disclosed modulated second radio frequency signal and a first radio frequency signal (which may serve as a reference signal to enable differential sensor (e.g., decoding). The apparatus may also include decoding circuitry. This decoding may be implemented at processor 280C and / or a separate chip or processor. The decoder may decodeVia Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564 the responsive radio frequency signal based on a difference between the first radio frequency signal and the modulated second radio frequency signal, wherein the difference indicates a value that varies based on a stimulus at a sensor at the remote apparatus. Moreover, the decoder may aligning the two channels using for example dynamic time warping or some other time alignment technology.

[0037] The reader 210 may be configured to transmit a probe radio frequency signal. This probe may comprise electromagnetic signals sent toward (e.g., as a query) a remote apparatus, such as RFID tags 305 and / or 307. In response to the probe radio frequency signal, the reader 210 may receive a responsive radio frequency signal carrying a modulated second radio frequency signal and a first radio frequency signal. As such, the reader’s decoder may decode (e.g., processor 280C or other device) the responsive radio frequency signal based on a difference between the first radio frequency signal and the modulated second radio frequency signal, wherein the difference indicates a value that varies based on a stimulus at a sensor at the remote apparatus.

[0038] In some implementations, the system 200 may be subject to interference, multipath, and / or the like. This may make it difficult for the RF reader 210 to properly receive the response 220B (which carries the sensor’s state, such as the indication of the stimulus being measured or detected by the sensor). To address the issue of multipath and / or other issues such as interference, the system 300 may be configured as depicted at FIG. 3A, in accordance with some embodiments.

[0039] The system 300 may include the impedance adjusted sensor 150, which is coupled to a second RFID transceiver 307 which may be the same or similar in some respects to the configuration noted above with respect to the RFID sensor 205 of the system 200 (FIG. 2). However, the system 300 further includes a first RFID transceiver 305, in accordance with some embodiments. This first RFID transceiver 305 is isolated from the second RFID transceiver 307 and the sensor 150. The transceivers may be implemented as noted above with respect to FIG. 2B, for example.

[0040] Referring to FIG. 3A, the outputs 309A-B of each of the first RFID tag 305 (also referred to as RFID circuitry and RFID transceiver) and the second RFID tag 307 are coupled to inputs 311A-B of a combiner 310. The combiner may comprise a Wilkinson combiner (alsoVia Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564 referred to as a Wilkinson power combiner). The output 313 of the Wilkinson combiner 310 is then coupled to an antenna 314.

[0041] In the example of FIG. 3A the second RFID transceiver 307 is connected to a resonance tuned sensor 150 such that impedance changes in sensor 150 can maximally impact the impedance of the transceiver. Furthermore, to improve power transfer from transmission line 311B connected to output terminal of Wilkinson Combiner 310 impedance matching may be used. The impedance of the RFID transceiver may have some impact on the resonant frequency of the sensor 150 which can be tuned by adjusting the value of tuning component in 112. But the first RFID transceiver 305 is isolated from the second RFID tag 307 and the sensor 150. In this way, when the RFID reader 210 queries 320A the RFID tag system 399, the response 320B includes information from the maximally coupled second RFID transceiver 307 (which carries the sensor’s 150 stimulus state information) and information from the isolated, first RFID transceiver 305. At the RFID reader 320, multipath and other interference will be present on both information channels (i.e., from RFID tags 305 and 307) but the sensor stimulus information is only present on the information channel from the second RFID tag 307. As such, the RFID reader 210 may then use differential sensing (e.g., decoding based on a difference between the two channels or path associated with the reference signal and the sensor modulated signal) to eliminate the multipath and interference and thus enhance the received sensor’s 150 stimulus state information.

[0042] In the example of FIG. 3A, the Wilkinson power combiner 310 passively merges the two signals (e.g., from the RFID transceivers 305 and 307) while providing high isolation between the two inputs. In the example of FIG. 3A for example, the two RFID tags 305A and 307 are sufficiently isolated (e.g., more than 25dB, although other isolation values may be used) from each other due to the isolation provided by the Wilkinson power combiner 310. As such, the two RFID tags 305 and 307 do not collide with each other when responding to the reader 210. More importantly, this isolation guarantees that the changes in sensor’s impedance only affects one RFID transceiver 307 while the other RFID transceiver 305 is largely immune from those changes.

[0043] In some embodiments, the Wilkinson power combiner 310 is present to split an incoming signal on for example a port (e.g., Port 1) to two equal halves at its Port 2 and Port 3 or reciprocally combines the two backscattered signals at its Port 1. The signal to the second tagVia Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564 307 may thus undergo modulation by the sensor whereas the signal to the first tag 305 is backscattered as is and recombined at Port 1, connected to an antenna 314 and then radiated back to the reader 210. The signals from the two tags 305 and 307 are separated by the virtue of their unique electronic product code (e.g., a globally unique code identifying an RFID tag) at the reader 210. A mathematical formulation of the same is given at Equation 3 wherein the phase difference ΔФ introduced by the sensor 150 is isolated from the random phase added by for example multipath ^ by virtue of the subtraction of phases of the code-separable signals in Sbx(t). For example, the phase change introduced by the sensor 150 can be recovered as ΔФ 350 given by the differential phase between the two tags 305 and 307 or ∠^^^^^(^). The same concept can be extended to differential amplitude as well. (3) (4)∠^^^(^) is the differential signal obtained by computing the difference of theby RFID transceivers 305 and 307; !"#(^) (320B) is the signal backscattered by the system (signal returned by RFID transceivers 305 / 307) which contains the signals of both 305 and 307 in alternate timeslots; $%(^)&'^ $((^) are the signals returned (backscattered)by transceivers 307, and 305 respectively; $%∗(^)&'^ $(∗(^)are the signals / identities known to the RFID reader 210 which are autocorrelated with the waveform returned by the system !"#(^); ∆Φ is the phase shift 350 introduced by the sensor connected to RFID transceiver in FIG. 3A; ^ is the random phase shift that is added by the wireless channel to the analog signal returned from the system; and -.represents the mathematical modelling of the impact of the wireless channel on the signals in a complex value format.Via Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564

[0044] At the reader 210, it may include or be coupled to one or more additional processors to, as noted, measure the sensor’s 150 phase changes (e.g., as ΔФ 350, or amplitude changes) and provide a real-time readout of the sensor. For example, the RFID reader 210 may cyclically hops through RFID channels, wherein each channel read may be about 200ms. The data is then processed (e.g., using dynamic time warping as disclosed herein) to correct for phase jumps introduced by, for example channel-hopping. Moreover, a user interface, such as graphical user interface, may be generated to display the sensor’s data over time.

[0045] FIG. 3B depicts another example implementation of the system 300 depicted at FIG. 3A. FIG. 3B is similar in some respects to FIG. 3A, but in the example of FIG. 3B a single RFID transceiver is shared. When a switch 316 is in a first position 386A for example, the circuitry 315 is configured such that the transceiver within the RFID circuitry 307 is coupled to the sensor 150 and then the sensor’s values (e.g., detected or measured values or variations) are modulated and transmitted along path 309B towards the antenna 314 and the reader 210. While in the second position 386B, the circuitry 315 is configured such that the transceiver within the RFID circuitry 307 provides a reference path (which is not coupled to the sensor 150), and the ID information transmitted along path 309A towards the antenna 314 and the reader 210. In this way, the circuitry 315 may be implemented using, for example, an RFID tag in accordance with RFID standards.

[0046] FIG. 3C depicts another example implementation of the system 300 depicted at FIG. 3A. FIG. 3C is similar in some respects to FIG. 3A, but in the example of FIG. 3C, the combiner 310 is replaced with a switch 3100. In this example, the switch 3100 isolates the sensor 150 from the reference path by switching over time between path 309A and 309B.

[0047] In some embodiments, the RFID tag 399 system may be configured to operate using a 15 millimeter by 10-millimeter flexible printed circuit board to couple the sensor 150, the second RFID tag 307, and the first RFID tag 305 to a single printed RFID antenna. While the RFID reader 210 reads the two RFID tags and the relative differential channel measurements to decode the sensor’s modulation (which indicates a stimulus being detected (e.g., measured) by the sensor). To illustrate an implementation example, the RFID tag 399 system was configured with a sensor comprising a capacitive soil moisture sensor. In this example, testing revealed thatVia Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564 the RFID tag system 399 may achieve over 93% accuracy in classifying three moisture levels with the soil moisture sensor.

[0048] Although some of the examples refer to a capacitive soil moisture sensor, other types of sensors may be used. Examples of the sensors include inductive coil-based sensors, inductive strain sensors, resistive force and temperature sensors, capacitive chemical sensors, and / or other types of sensors or devices.

[0049] In some embodiments, the RFID reader 210 comprises at least one processor and at least one memory configured with instructions to provide a low-latency RFID reader software algorithm (e.g., Impinj Speedway, SLLURP, and / or the like).

[0050] FIGs. 6 and 7 depict an example of dynamic time warping used to correct for phase jumps introduced by for example channel-hopping related to RFID tag transmission. FIG. 6 shows how the disclosed RFID reader may use dynamic time warping (DTW) to temporally align the phase sequences of two differential RFID tags, such as tag 305 and tag 307. Each circle and triangle represent a phase measurement across time and frequency channels, with arrows showing the DTW warping path that matches asynchronous samples. By aligning these sequences within each channel, this ensures that reliable differential phase values can be computed despite reader-induced timing mismatches.

[0051] FIG. 7 shows how the differential phase is computed between two RFID tags, such as tag 305 and 307, across multiple frequency channels. The circles (e.g., tag 305) and triangles (e.g., tag 307) represent phase samples collected within each channel, and the vertical difference between them indicates the per-channel phase difference. The boxed equations formalize this: first computing the absolute phase difference for each aligned sample pair within a channel and then aggregating across all the channels to obtain the final consolidated differential phase, which serves as the sensing signal.

[0052] In some embodiments, the RFID reader 210 (or a coupled processor) may be configured to perform real-time differential sensing. For example, sequential channel state information may be received from the first RFID transceiver 305 and the second RFID transceiver 307 from for example the RFID reader 210 (or a processor-based device coupled or included therein). The sequential processing may introduce temporal misalignment τ between afirst phase sequence Φ%(^ + 0) and a second phase sequence Φ((^). Next, the first phasesequence and the second phase sequence may be extracted from the first RFID transceiver andVia Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564 the second RFID transceiver respectively for each frequency channel c within a predetermined time frame of four frequency channels corresponding to 0.8 seconds of data collection.

[0053] Next, a dynamic time warping algorithm may be applied to align the temporally misaligned first phase sequence and second phase sequence on a per-channel basis, such that said the dynamic time warping algorithm determines (e.g., computes) an optimal warping path W by minimizing a cost function D(i,j) = d(φ₁(t^), φ₂(t^)) + min{D(i-1,j), D(i,j-1), D(i-1,j-1)}. And, the determination may further include computing differential measurements Φdiff(t^) = |Φ₁(t^) - Φ₂(t^)| for all aligned timestamps t^ ∈ W. The sensor output data may be generated with sub-second stimulus resolution representing for example a 5 fold improvement in sensing speed over existing differential sensing techniques.

[0054] As noted, the dynamic time warping algorithm addresses the problem of temporal misalignment between two streams of RFID signal data (e.g., phase measurements) from distinct tags in a differential sensing setup. The dynamic time warping process enables optimal alignment of these asynchronously received sequences, ensuring accurate differential analysis regardless of non-uniform sampling intervals or shifting read times, which commonly occur due to sequential reader operation and varying tag energy harvesting rates.

[0055] To illustrate further and referring to FIGs. 6 and 7, RFID readers may process tag signals in sequence, resulting in non-simultaneous sampling and arbitrary time shifts (τ) between measurements from the two tags used in differential sensing. Without proper alignment of these sequences, directly computing the difference (e.g., phase or RSSI) would introduce large errors, compromising the accuracy and robustness of the sensing outcome. The dynamic time warping may be used to provide a sequence matching process. For example, the input data may correspond to two time-indexed sequences of signal measurements (e.g., phase values) from two tags (which may be of unequal length or received at different times) represented as follows: • Φ1 = {ϕ1(t1), ϕ1(t2), ..., ϕ1(tN)} • Φ2 = {ϕ2(t1), ϕ2(t2), ..., ϕ2(tM)}Via Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564

[0056] Next, a cost matrix D of size N×M is initialized, and boundary conditions are set (e.g., D(0,0) = 0), where all other first row / column entries are set to infinity. For every pair of samples (i, j), the DTW algorithm computes the distance d(ϕ1(ti), ϕ2(tj)) = ∣ϕ1(ti) - ϕ2(tj)|. Next, the algorithm updates D(i,j) as the computed distance plus the minimum cost from adjacent previous steps (D(i−1, j), D(i,j−1), D(i−1,j−1)), enforcing alignment while handling variations in sampling rate. To extract a warping path, the DTW algorithm may start from D(N, M) and backtrack to find a sequence of matched indices (W), which define the optimal alignment between the input sequences. To determine an aligned differential computation, for each matched time pair (ti,tj) on W, the differential measurement (e.g., phase difference) may be determined as follows: Φdiff (ti) = ∣ϕ1(ti)−ϕ2(tj)∣. The DTW process outputs both the minimum total alignment cost and the set of aligned sample pairs, enabling temporally accurate differential sensing across noisy, misaligned data streams.

[0057] In some embodiments, there may be provided a differential sensing system that includes an RFID reader configured to process RF transceivers sequentially according to framed slotted ALOHA protocol at frequencies between 902-928 MHz divided into 50 frequency channels; at least two RFID transceivers may be coupled to a shared antenna through a Wilkinson power combiner (or, e.g., a switch), wherein a first RFID transceiver of said at least two RFID transceivers serves as a sensor-modulated tag and a second RFID transceiver of said at least two RFID transceivers serves as a reference tag. Moreover, there may be provided a computing device interfacing with the commercial RFID reader to achieve a throughput of at least 800 RF transceiver reads per second (which may represent an 8 fold improvement over low-level protocol implementations). Furthermore, a processor configured to execute preset reader configurations including expected tag population and optimized frame size settings to maximize resource allocation. The system may process differential sensing data at for example 400 sensory samples per second compared to existing systems operating at for example 50 sensory samples per second.

[0058] In some embodiments, there is provided a process for mitigating frequency hopping artifacts in RFID differential sensing. For example, phase sequences may be monitored from a plurality of RFID transceivers across frequency channels within a 902-928 MHz range,Via Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564 wherein the RFID readers may introduce arbitrary π phase jumps during frequency transitions occurring approximately 15% of the time. Next, the phase data may be independently processed for each frequency channel with a 200ms dwell time to avoid cross-channel phase discontinuities. Next, the channel stability may be determined by identifying at least three stable channels from four channel hops with 90% statistical confidence based on binomial probability analysis. In addition, temporal alignment algorithms may be applied exclusively within individual frequency channels to preserve phase consistency while avoiding artifacts from frequency switching mechanisms. Next, the aligned differential phase measurements from multiple stable channels may be consolidated to generate robust sensor readings immune to frequency hopping-induced phase ambiguities.

[0059] In some embodiments, a calibration system may be performed for the RFID system. For example, a rigid printed circuit board comprising two RFID transceivers positioned at predetermined electrical lengths calculated at effective wavelength 34within substrate material. The calibration system may include a shared antenna coupled to the two RFID transceivers through a Wilkinson power combiner creating distinct signal path lengths. The transmission line stubs may be configured to introduce fixed phase shifts of 5.95° per signal path, resulting in a net differential phase of 11.9° for backscattered signals, wherein the predetermined electrical lengths generate calculable phase differences between incident and backscattered signals providing known ground truth for performance evaluation, and wherein the calibration system enables benchmarking of differential sensing algorithms under both optimal conditions without multipath interference and challenging environments with significant multipath effects.

[0060] Although some of the examples refer to the RFID tag system 399 as passive (i.e., without battery), the RFID tag system 399 may be configured with an active power source, such as a battery, as well. Additional Examples

[0061] To directly profile a sensor’s impedance at RF, the sensor may be treated as an antenna, to obtain the scattering parameters (S11 measurement). The S11 plot is obtained by exciting the sensor at a particular RF frequency, and observing the resultant amplitude / phase change back from the sensor. An observation is that the sensors couple more efficiently atVia Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564 certain frequencies over others called resonant frequencies as depicted at FIG. 1. In other words, at these resonant frequencies the sensor responsiveness to a change in the stimulus is at its best.

[0062] However, in order to measure !11 parameters of the sensor, the sensor may be excited with RF signals in a series 402 or a shunt 404 configuration as shown at FIG. 4. In sensors which have resistive dominance, it is ideal for a series interface, since a resistance in shunt results in heavier signal losses. On the other hand, if a sensor is reactive dominant, the sensor should be interfaced in shunt configuration. In the RFID tag system 399, this concept of sensor resonance, as well as correct series / shunt configuration, is used to ensure maximal coupling of energy from the stimulus to its output impedance.

[0063] In some implementations, the current subject matter may be configured to be implemented in a system as shown in FIG. 5. For example, the RFID reader may include or be coupled to some if not all of the aspects of the system noted with respect to FIG. 5. To illustrate further, the system may further include an operating system, a hypervisor, and / or other resources, to provide the noted machine learning models. The system may include a processor 910, a memory 920, a storage device 930, and an input / output device 940. Each of the components (e.g., 910, 920, 930 and 940) may be interconnected using a system bus 950. The processor 910 may be configured to process instructions for execution within the system 900. In some implementations, the processor 910 may be a single-threaded processor. In alternate implementations, the processor 910 may be a multi-threaded processor. In some embodiments, the processor 910 may include multiple processors, graphics processing units (GPUs), machine learning or AI chips / processors, which can be used for training and / or inference.

[0064] The processor 910 may be further configured to process instructions stored in the memory 920 or on the storage device 930, including receiving or sending information through the input / output device 940. The memory 920 may store information within the system 900. In some implementations, the memory 920 may be a computer-readable medium. In alternate implementations, the memory 920 may be a volatile memory unit. In some implementations, the memory 920 may be a non-volatile memory unit. The storage device 930 may be capable of providing mass storage for the system 900. In some implementations, the storage device 930 may be a computer-readable medium. In alternate implementations, the storage device 930 may be a floppy disk device, a hard disk device, an optical disk device, a tape device, non-volatile solid state memory, or any other type of storage device. The input / output device 940 may beVia Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564 configured to provide input / output operations for the system 900. In some implementations, the input / output device 940 may include a keyboard and / or pointing device. In alternate implementations, the input / output device 940 may include a display unit for displaying graphical user interfaces.

[0065] Referring again to FIGs. 3A-3C, there may be provided an apparatus comprising a sensor, such as sensor 150, configured to provide a value that varies based on a stimulus at the sensor 150. In the case of a moisture sensor or other type of sensor for example, the moisture detected or measures may be captured as a value at the sensor which may vary over time. The apparatus may include at least one radio frequency transceiver circuitry coupled to the sensor. For example, the at least one radio frequency transceiver circuitry may comprise two RFID transceivers or tags, such as 305 and 307 at FIG. 3A. Alternatively, or additionally, the at least one radio frequency transceiver circuitry may comprise a single RFID tag, such as tag 307. Moreover, the at least one radio frequency transceiver circuity may generate a first radio frequency signal, such as a reference signal provided along path 309A, for example. And, the at least one radio frequency transceiver circuity may generate a second radio frequency signal, such as the modulated RF signal along path 309B. The sensor’s measured or detected value (indicative of the stimulus) may be used to modulate a phase and / or an amplitude of the second radio frequency signal. The apparatus may also include an antenna, such as antenna 314.

[0066] Moreover, the at least one radio frequency transceiver circuitry (which as noted is coupled to a sensor) may receive an electromagnetic signal from, for example reader 210. The sensor is configured to provide a value that varies based on a stimulus at the sensor. Moreover, the variation in the value modulates a phase and / or an amplitude of a second radio frequency signal generated by the at least one radio frequency transceiver circuitry. In response to an electromagnetic signal, the at least one radio frequency transceiver may transmit a first radio frequency signal and the modulated second radio frequency signal toward, for example the reader 210. The first radio frequency signal may serve as a reference to enable decoding (e.g., differential decoding using a difference between first radio frequency signal and the modulated second radio frequency signal). The decoding yields information indicative of the value that varies at the sensor.Via Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564

[0067] Although some of the examples show 1 or 2 tags, other quantities of tags may be used as well. Moreover, one or more aspects disclosed with respect to a given figure may be used with other examples given with respect another given figure.

[0068] Although some of the examples refer to RFID, other radio technologies may be used. For example, WiFi backscatter, Bluetooth low energy (BLE) backscatter, Ambient IoT, and / or the like may be used. Alternatively, or additionally, these radio technologies may include more active transceiver technology, such as WiFi, Bluetooth, BLE, LTE, 5G NR, 6G, and / or other radio technologies.

[0069] In view of the above-described implementations of subject matter this application discloses the following list of examples, wherein one feature of an example in isolation or more than one feature of said example taken in combination and, optionally, in combination with one or more features of one or more further examples are further examples also falling within the disclosure of this application:

[0070] Example 1. An apparatus comprising: a sensor configured to provide a value that varies based on a stimulus at the sensor; at least one radio frequency transceiver circuitry coupled to the sensor, wherein the at least one radio frequency transceiver circuity generates a first radio frequency signal and a second radio frequency signal, wherein the variation in the value modulates a phase and / or an amplitude of the second radio frequency signal generated by the at least one radio frequency transceiver circuitry; and an antenna configured to transmit the modulated second radio frequency signal and the first radio frequency signal.

[0071] Example 2. The apparatus of Example 1, wherein the at least one radio frequency transceiver circuitry comprises a first radio frequency transceiver circuitry and a second radio frequency transceiver circuitry, wherein the second radio frequency transceiver circuitry is coupled to the sensor and generates the modulated second radio frequency signal.Via Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564

[0072] Example 3. The apparatus of any of Examples 1-2, wherein the first radio frequency transceiver circuitry is isolated from the second radio frequency transceiver circuitry and the sensor.

[0073] Example 4. The apparatus of any of Examples 1-3, wherein the at least one radio frequency transceiver circuitry comprises a first radio frequency transceiver circuitry coupled to a switch, wherein the switch in a first position provides the first radio frequency signal toward the antenna, and the switch in a second position provides the modulated second radio frequency signal toward the antenna.

[0074] Example 5. The apparatus of any of Examples 1-4, wherein the at least one radio frequency transceiver circuitry comprises radio frequency identification (RFID) circuity.

[0075] Example 6. The apparatus of any of Examples 1-5, wherein the at least one radio frequency transceiver circuitry comprises passive circuitry.

[0076] Example 7. The apparatus of any of Examples 1-6, wherein the at least one radio frequency transceiver circuitry comprises active circuitry.

[0077] Example 8. The apparatus of any of Examples 1-7, further comprising: a combiner and / or a switch coupled to the at least one radio frequency transceiver circuitry, wherein the combiner and / or the switch isolates the sensor from the first radio frequency signal.

[0078] Example 9. The apparatus of any of Examples 1-8, wherein the combiner comprises a Wilkinson power combiner, and / or wherein the combiner and / or the switch is further coupled to the antenna.Via Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564

[0079] Example 10. The apparatus of any of Examples 1-9, wherein a differential between the modulated second radio frequency signal and the first radio frequency signal communicates information indicative of the value that varies at the sensor.

[0080] Example 11. The apparatus of any of Examples 1-10, wherein the modulated second radio frequency signal and the first radio frequency signal are transmitted in response to an electromagnetic signal.

[0081] Example 12. The apparatus of any of Examples 1-11, wherein the electromagnetic signal is received from a reader, and / or wherein the modulated second radio frequency signal and the first radio frequency signal are transmitted toward the reader.

[0082] Example 13. The apparatus of any of Examples 1-12, wherein the reader comprises a radio frequency identification reader.

[0083] Example 14. The apparatus of any of Examples 1-13, wherein the sensor is configured with a resonant frequency that is adjusted to a radio frequency within a communication band.

[0084] Example 15. The apparatus of any of Examples 1-14, wherein the communication band is a radio frequency identification communication band.

[0085] Example 16. An apparatus comprising: transceiver circuitry configured to transmit a probe radio frequency signal to a remote apparatus and to receive a responsive radio frequency signal carrying a modulated second radio frequency signal and a first radio frequency signal; and decoding circuitry configured to decode the responsive radio frequency signal based on a difference between the first radio frequency signal and the modulated second radio frequency signal, wherein the difference indicates a value that varies based on a stimulus at a sensor at the remote apparatus.Via Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564

[0086] Example 17. The apparatus of Example 16, wherein the remote apparatus comprises the apparatus of claim 1.

[0087] Example 18. The apparatus of any of Examples 16-17, wherein the decoding circuitry is configured to decode using two channels comprising the modulated second radio frequency and the first radio frequency signal.

[0088] Example 19. The apparatus of any of Examples 16-19, wherein the decoding comprises aligning the two channels.

[0089] Example 20. The apparatus of any of Examples 1-19, wherein the apparatus comprises a radio frequency identification reader.

[0090] Example 21. A method comprising: receiving, by at least one radio frequency transceiver circuitry coupled to a sensor, an electromagnetic signal, wherein the sensor is configured to provide a value that varies based on a stimulus at the sensor, wherein the variation in the value modulates a phase and / or an amplitude of a second radio frequency signal generated by the at least one radio frequency transceiver circuitry; and in response an electromagnetic signal, transmitting a first radio frequency signal and the modulated second radio frequency signal, wherein the first radio frequency signal serves as a reference to enable decoding, based on a difference between first radio frequency signal and the modulated second radio frequency signal, information indicative of the value that varies at the sensor.

[0091] Example 22. A method comprising: transmitting a probe radio frequency signal to a remote apparatus; receiving, in response to the probe radio frequency signal, a responsive radio frequency signal carrying a modulated second radio frequency signal and a first radio frequency signal; andVia Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564 decoding the responsive radio frequency signal based on a difference between the first radio frequency signal and the modulated second radio frequency signal, wherein the difference indicates a value that varies based on a stimulus at a sensor at the remote apparatus.

[0092] One or more aspects or features of the subject matter described herein can be realized in digital electronic circuitry, transceiver, specially designed ASICs, field programmable gate arrays (FPGAs) computer hardware, firmware, software, and / or combinations thereof. These various aspects or features can include implementation in one or more computer programs that are executable and / or interpretable on a programmable system including at least one programmable processor, which can be special or general purpose, coupled to receive data and instructions from, and to transmit data and instructions to, a storage system, at least one input device, and at least one output device. The programmable system or computing system may include clients and servers. A client and server are generally remote from each other and typically interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other.

[0093] These computer programs, which can also be referred to as programs, software, software applications, applications, components, or code, include machine instructions for a programmable processor, and can be implemented in a high-level procedural and / or object- oriented programming language, and / or in assembly / machine language. As used herein, the term “machine-readable medium” refers to any computer program product, apparatus and / or device, such as for example magnetic discs, optical disks, memory, and Programmable Logic Devices (PLDs), used to provide machine instructions and / or data to a programmable processor, including a machine-readable medium that receives machine instructions as a machine-readable signal. The term “machine-readable signal” refers to any signal used to provide machine instructions and / or data to a programmable processor. The machine-readable medium can store such machine instructions non-transitorily, such as for example as would a non-transient solid- state memory or a magnetic hard drive or any equivalent storage medium. The machine-readable medium can alternatively or additionally store such machine instructions in a transient manner,Via Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564 such as for example, as would a processor cache or other random access memory associated with one or more physical processor cores.

[0094] To provide for interaction with a user, one or more aspects or features of the subject matter described herein can be implemented on a computer having a display device, such as for example a cathode ray tube (CRT) or a liquid crystal display (LCD) or a light emitting diode (LED) monitor for displaying information to the user and a keyboard and a pointing device, such as for example a mouse or a trackball, by which the user may provide input to the computer. Other kinds of devices can be used to provide interaction with a user as well. For example, feedback provided to the user can be any form of sensory feedback, such as visual feedback, auditory feedback, or tactile feedback; and input from the user may be received in any form, including acoustic, speech, or tactile input. Other possible input devices include touch screens or other touch-sensitive devices such as single or multi-point resistive or capacitive track pads, voice recognition hardware and software, optical scanners, optical pointers, digital image capture devices and associated interpretation software, and the like.

[0095] In the descriptions above and in the claims, phrases such as “at least one of” or “one or more of” may occur followed by a conjunctive list of elements or features. The term “and / or” may also occur in a list of two or more elements or features. Unless otherwise implicitly or explicitly contradicted by the context in which it used, such a phrase is intended to mean any of the listed elements or features individually or any of the recited elements or features in combination with any of the other recited elements or features. For example, the phrases “at least one of A and B;” “one or more of A and B;” and “A and / or B” are each intended to mean “A alone, B alone, or A and B together.” A similar interpretation is also intended for lists including three or more items. For example, the phrases “at least one of A, B, and C;” “one or more of A, B, and C;” and “A, B, and / or C” are each intended to mean “A alone, B alone, C alone, A and B together, A and C together, B and C together, or A and B and C together.” Use of the term “based on,” above and in the claims is intended to mean, “based at least in part on,” such that an unrecited feature or element is also permissible.

[0096] The subject matter described herein can be embodied in systems, apparatus, methods, and / or articles depending on the desired configuration. The implementations set forth in the foregoing description do not represent all implementations consistent with the subject matter described herein. Instead, they are merely some examples consistent with aspects relatedVia Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564 to the described subject matter. Although a few variations have been described in detail above, other modifications or additions are possible. In particular, further features and / or variations can be provided in addition to those set forth herein. For example, the implementations described above can be directed to various combinations and subcombinations of the disclosed features and / or combinations and subcombinations of several further features disclosed above. In addition, the logic flows depicted in the accompanying figures and / or described herein do not necessarily require the particular order shown, or sequential order, to achieve desirable results. Other implementations may be within the scope of the following claims.

Claims

Via Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564 CLAIMS What is claimed:

1. An apparatus comprising: a sensor configured to provide a value that varies based on a stimulus at the sensor; at least one radio frequency transceiver circuitry coupled to the sensor, wherein the at least one radio frequency transceiver circuity generates a first radio frequency signal and a second radio frequency signal, wherein the variation in the value modulates a phase and / or an amplitude of the second radio frequency signal generated by the at least one radio frequency transceiver circuitry; and an antenna configured to transmit the modulated second radio frequency signal and the first radio frequency signal.

2. The apparatus of claim 1, wherein the at least one radio frequency transceiver circuitry comprises a first radio frequency transceiver circuitry and a second radio frequency transceiver circuitry, wherein the second radio frequency transceiver circuitry is coupled to the sensor and generates the modulated second radio frequency signal.

3. The apparatus of claim 2, wherein the first radio frequency transceiver circuitry is isolated from the second radio frequency transceiver circuitry and the sensor.

4. The apparatus of claim 1, wherein the at least one radio frequency transceiver circuitry comprises a first radio frequency transceiver circuitry coupled to a switch, wherein the switch in a first position provides the first radio frequency signal toward the antenna, and the switch in a second position provides the modulated second radio frequency signal toward the antenna.

5. The apparatus of claim 1, wherein the at least one radio frequency transceiver circuitry comprises radio frequency identification (RFID) circuity.Via Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564 6. The apparatus of claim 1, wherein the at least one radio frequency transceiver circuitry comprises passive circuitry.

7. The apparatus of claim 1, wherein the at least one radio frequency transceiver circuitry comprises active circuitry.

8. The apparatus of claim 1, further comprising: a combiner and / or a switch coupled to the at least one radio frequency transceiver circuitry, wherein the combiner and / or the switch isolates the sensor from the first radio frequency signal.

9. The apparatus of claim 8, wherein the combiner comprises a Wilkinson power combiner, and / or wherein the combiner and / or the switch is further coupled to the antenna.

10. The apparatus of claim 1, wherein a differential between the modulated second radio frequency signal and the first radio frequency signal communicates information indicative of the value that varies at the sensor.

11. The apparatus of claim 1, wherein the modulated second radio frequency signal and the first radio frequency signal are transmitted in response to an electromagnetic signal.

12. The apparatus of claim 9, wherein the electromagnetic signal is received from a reader, and / or wherein the modulated second radio frequency signal and the first radio frequency signal are transmitted toward the reader.

13. The apparatus of claim 12, wherein the reader comprises a radio frequency identification reader.

14. The apparatus of claim 1, wherein the sensor is configured with a resonant frequency that is adjusted to a radio frequency within a communication band.Via Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564 15. The apparatus of claim 14, wherein the communication band is a radio frequency identification communication band.

16. An apparatus comprising: transceiver circuitry configured to transmit a probe radio frequency signal to a remote apparatus and to receive a responsive radio frequency signal carrying a modulated second radio frequency signal and a first radio frequency signal; and decoding circuitry configured to decode the responsive radio frequency signal based on a difference between the first radio frequency signal and the modulated second radio frequency signal, wherein the difference indicates a value that varies based on a stimulus at a sensor at the remote apparatus.

17. The apparatus of claim 16, wherein the remote apparatus comprises the apparatus of claim 1.

18. The apparatus of claim 16, wherein the decoding circuitry is configured to decode using two channels comprising the modulated second radio frequency and the first radio frequency signal.

19. The apparatus of claim 18, wherein the decoding comprises aligning the two channels.

20. The apparatus of claim 16, wherein the apparatus comprises a radio frequency identification reader.

21. A method comprising: receiving, by at least one radio frequency transceiver circuitry coupled to a sensor, an electromagnetic signal, wherein the sensor is configured to provide a value that varies based on a stimulus at the sensor, wherein the variation in the value modulates a phaseVia Patent Center Docket No.: 24636-773WO1 / 2025-068-2 Filing Date: September 19, 2025 Customer No.: 39564 and / or an amplitude of a second radio frequency signal generated by the at least one radio frequency transceiver circuitry; and in response an electromagnetic signal, transmitting a first radio frequency signal and the modulated second radio frequency signal, wherein the first radio frequency signal serves as a reference to enable decoding, based on a difference between first radio frequency signal and the modulated second radio frequency signal, information indicative of the value that varies at the sensor.

22. A method comprising: transmitting a probe radio frequency signal to a remote apparatus; receiving, in response to the probe radio frequency signal, a responsive radio frequency signal carrying a modulated second radio frequency signal and a first radio frequency signal; and decoding the responsive radio frequency signal based on a difference between the first radio frequency signal and the modulated second radio frequency signal, wherein the difference indicates a value that varies based on a stimulus at a sensor at the remote apparatus.

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