Abstract: A method begins by a radio frequency identification (RFID) reader transmitting a first and second radio frequency (RF) signal of a plurality of RF signals, which each include a unique carrier frequency and an instruction to an RFID tag to respond with a received power level indication. The method continues by the RFID reader receiving, in response to the first and second signals sent at a first and second carrier frequency, a first and second response from the RFID tag that includes a first and second received power level indication. The method continues by the RFID reader determining an estimated resonant frequency of the RFID tag based on the first and second received power level indications and the first and second carrier frequencies. The method continues by the RFID reader determining an environmental condition based on the estimated resonant frequency.

Abstract: A radio frequency identification (RFID) tag includes an antenna, a power circuit, a tuning circuit, a receiver, and a backscatter transmitter. The power circuit is operably coupled to convert a radio frequency (RF) signal received via the antenna from an RFID reader into one or more power supply voltages. The tuning circuit is operably coupled to the antenna and to adjust an RF characteristic of the antenna and/or the tuning circuit based on a difference between a resonant frequency of the RFID tag and a carrier frequency of the RF signal. The receiver is operably coupled to receive a command signal from the RFID reader. The backscatter transmitter is operably coupled to transmit a response signal to the RFID reader via the antenna.

Abstract: A radio frequency identification (RFID) tag includes an antenna, an analog front end, a processing circuit, and memory. The analog front end includes a power circuit, a tuning circuit, a transmitter, and a receiver. The power circuit is operably coupled to convert a radio frequency (RF) signal into a power supply voltage. The tuning circuit, when enabled, adjusts an RF characteristic of the analog front end to tune power harvesting from the RF signal. The transmitter is operably coupled to transmit a response signal to the RFID reader via the antenna. The receiver is operably coupled to receive a command signal from the RFID reader, wherein the command signal is contained within a portion of the RF signal. The processing circuit is operable to interpret the command signal and generate the response signal.

Abstract: A label sensor that can be affixed to an item includes a first section and a second section. The first section includes a memory, an environmental sensor, a radio frequency (RF) front end that includes a tuning circuit, and a processing module. The processing module is operably coupled to the memory, the environmental sensor, and the RF front end. The second section includes an activation circuit that is operable, upon receiving an input, to activate one or more of the memory, the environmental sensor, the RF front end and the processing module. The activation causes the label sensor to be put in a first operational mode of a plurality of operational modes.

Abstract: A radio frequency identification (RFID) tag includes a power harvesting circuit, an RF front-end, and a processing module. The power harvesting circuit generates power for the RFID tag from a continuous wave of an inbound radio frequency (RF) signal. The RF front-end receives the inbound RF signal and transmits an outbound RF signal. The RF front-end includes a tuning circuit that is tuned based on a capacitance setting. The tuning of the tuning circuit effects a characteristic of the RF front-end. The processing module generate the capacitance setting to adjust the characteristic of the RF front-end to a desired characteristic.

Abstract: A wireless sensor includes a radio frequency (RF) receiving circuit operable to receive an RF signal having a carrier frequency of a plurality of carrier frequencies. The RF receiving circuit further includes a variable impedance where impedance of the variable impedance is a factor in establishing a resonant frequency of the RF receiving circuit. The wireless sensor further includes a processing module that is operable to determine a first value for a first impedance of the variable impedance for a known temperature based on the resonant frequency and the carrier frequency, determine a second value a second impedance of the variable impedance for an unknown temperature based on the resonant frequency and the carrier frequency, and determine a difference between the first and second values that corresponds to a change between the known temperature and the unknown temperature.

Abstract: A method includes a computing device transmitting a radio frequency (RF) signal to a passive wireless sensor. The RF signal includes a carrier frequency signal and a modulated sense request signal. The method further includes, in response to the modulated sense request signal, receiving, by the computing device, a response RF signal that includes the carrier frequency signal and a coded sense response signal from the passive wireless sensor. The coded sense response signal is representative of a sensed environmental condition by the passive wireless sensor. The method further includes generating, by the computing device, an environmental condition value based on the coded sense response signal and an environmental conversion information.

Abstract: A method includes sending, by a reader, a radio frequency (RF) signal to a wireless sensor that includes an antenna having a tail section and a head section. The tail section is for placement in an RF limited area for sensing moisture in a first location of a vehicle under test and wherein the head section is for placement in a non-RF limited area. The method further includes receiving, by the reader, an RF response to the RF signal from the wireless sensor. The first RF response includes an indication of adjustment of one or more RF characteristics of the wireless sensor, which corresponds to a variance of the one or more RF characteristics from a desired value, which, in turn, corresponds to a level of moisture at the first location. The method further includes outputting, by the reader, a message regarding the level of moisture at the first location.

Abstract: A method for execution by a RFID tag includes receiving, by an antenna of the RFID tag, an RF signal from an RFID reader, where the RF signal has a carrier frequency. The method further includes determining, by a tuning circuit of the RFID tag, a received power level of the RF signal at the carrier frequency and whether the received power level compares favorably to a power level threshold. When the received power level compares unfavorably to the power level threshold, the method further includes adjusting, by the tuning circuit, the input impedance of the RFID tag by adjusting a tank circuit of the RFID tag until the received power level compares favorably to the power level threshold, where the input impedance of the RFID tag is based on one or more of impedance of the antenna and impedance of the tank circuit.

Abstract: A power detector for use in an RF receiver. The detector includes a power reference generator and a power quantizer. The power reference generator develops a power reference current, voltage, or signal as a function of a power transferred via a received RF signal. The power quantizer is responsive to the power reference current, voltage, or signal to develop a digital field power value indicative of the power reference current, voltage, or signal.

Abstract: A radio frequency identification (RFID) tag includes an antenna structure, a tank circuit, and a processing module that includes a tuning circuit. The processing module requires a processing module power level to operate according to a protocol. The tuning circuit requires a tuning circuit power level to adjust input impedance. The processing module power level is greater than the tuning circuit level. The processing module measures a first power level from a received RF signal. When the first power level is greater than the tuning circuit power level but less than the processing module power level, the processing module adjusts the input impedance to increase efficiency of power measurement and measures a second power level from the received RF signal. When and the second power level is greater than the processing module power level, the processing module uses the second power level to operate according to the protocol.

Abstract: An improved AC-to-DC charge pump for use, for example, in voltage generation circuits. In one embodiment, two 2-diode charge pumps are coupled in back-to-back configuration, and adapted to develop a substantially stable voltage on a mid-level rail. In one other embodiment, two 3-diode charge pumps are coupled in back-to-back configuration, and adapted also to develop a substantially stable voltage on a mid-level rail. In one preferred embodiment, all diodes are implemented as current-source-biased MOSFETs.

Abstract: A method includes sending, by a reader, a radio frequency (RF) signal to a wireless sensor that includes an antenna having a tail section and a head section. The tail section is for placement in an RF limited area for sensing moisture in a first location of a vehicle under test and wherein the head section is for placement in a non-RF limited area. The method further includes receiving, by the reader, an RF response to the RF signal from the wireless sensor. The first RF response includes an indication of adjustment of one or more RF characteristics of the wireless sensor, which corresponds to a variance of the one or more RF characteristics from a desired value, which, in turn, corresponds to a level of moisture at the first location. The method further includes outputting, by the reader, a message regarding the level of moisture at the first location.

Abstract: A label sensor that can be affixed to an item includes a first section and a second section. The first section includes a memory, an environmental sensor, a radio frequency (RF) front end that includes a tuning circuit, and a processing module. The processing module is operably coupled to the memory, the environmental sensor, and the RF front end. The second section includes an activation circuit that is operable, upon receiving an input, to activate one or more of the memory, the environmental sensor, the RF front end and the processing module. The activation causes the label sensor to be put in a first operational mode of a plurality of operational modes.

Abstract: A power detector for use in an RF receiver. The detector includes a power reference generator and a power quantizer. The power reference generator develops a power reference current, voltage, or signal as a function of a power transferred via a received RF signal. The power quantizer is responsive to the power reference current, voltage, or signal to develop a digital field power value indicative of the power reference current, voltage, or signal.

Abstract: A power detector for use in an RF receiver. The detector includes a power reference generator and a power quantizer. The power reference generator develops a power reference current, voltage, or signal as a function of a power transferred via a received RF signal. The power quantizer is responsive to the power reference current, voltage, or signal to develop a digital field power value indicative of the power reference current, voltage, or signal.

Abstract: A wireless sensor includes a radio frequency (RF) front end, a sensing element, and a processing module. The RF front end receives a request for sensed data from a sensing computing device and sends a coded digital value to the sensing computing device via the RF signal. The sensing element senses an environmental condition of an item. The processing module determines an effect on an operational parameter of an RF front end of the wireless sensor as a result of the sensing element sensing the environmental condition and while receiving the RF signal. The processing module also adjusts tuning of the RF front end to mitigate the effect on the operational parameter and equates an amount of adjusting of the tuning of the RF front end to a coded digital value.

Abstract: A label sensor that can be affixed to an item includes a first section and a second section. The first section includes a memory, an environmental sensor, a radio frequency (RF) front end, and a processing module. The processing module is operably coupled to the memory, the environmental sensor, and the RF front end. The second section includes an activation circuit that is operable, upon receiving an input, to activate one or more of the memory, the environmental sensor, the RF front end and the processing module. The activation causes the label sensor to be put in an operational mode of a plurality of operational modes.

Abstract: A method includes varying, by a tuning module of a passive radio RFID sensor, a reactive component impedance coupled to the tuning module and an antenna of the passive RFID sensor in order to change a system impedance. The method further includes producing an impedance value representative of the reactive component's impedance. The method further includes storing, by a memory module of the passive RFID sensor, the impedance value, identification information corresponding to the antenna, and a timestamp corresponding to the impedance value. The method further includes communicating, by a wireless communication module of the passive RFID sensor, the impedance value, the identification information, and the timestamp to an RFID reader. When the impedance value, the identification information, and the timestamp indicate an unfavorable environmental condition, the method further includes generating, by the RFID reader, an alarm signal.

Abstract: A wireless sensor includes a substrate, an antenna, a sensing element, a transmission line, and a sensing integrated circuit (IC). The sensing element is positioned on one end of the substrate and the antenna is positioned on an opposite end of the substrate. The sensing IC is coupled to the sensing element and to the antenna via the transmission line. The sensing IC is operable to receive a sensed condition of the item from the sensing element. The sensing IC is further operable to determine an input impedance of the wireless sensor based on the sensed condition and convert it into a digital value that is representative of the condition of the item. The sensing IC is further operable to output, via the antenna, the digital value or a representation of the condition of the item.