Abstract: A radio frequency identification (RFID) tag includes a power harvesting circuit that operates generate power for the RFID tag from a continuous wave of a radio frequency (RF) signal. The RFID tag further includes a tuning circuit that is tuned based on a capacitance setting, where the capacitance setting is indicative of a power level of the power. The RFID tag further includes a processing module operably coupled to the tuning circuit, where the processing module operates to generate the capacitance setting to obtain a desired power level for the power.

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 method includes processing, by a processing module of a data logging device, a plurality of log commands. The processing of a log command of the plurality of log commands includes obtaining a measure of an environmental condition. The processing further includes updating a status of the environmental condition based on the measure of an environmental condition. The method further includes determining, by the processing module, the updated status of the environmental condition after the plurality of log commands have been processed. When the updated status of the environmental condition is favorable, the method further includes generating, by the processing module, a favorable environmental condition signal.

Abstract: A method includes establishing, by a data logging device, a sleep mode. The method further includes receiving, by a processing module of the data logging device, a second activation command that causes the data logging device to transition to a standby mode. The method further includes receiving, by the processing module, a third activation command that causes the data logging device to transition to a ready mode. The method further includes receiving, by the processing module, a fourth activation command that causes the data logging device to transition to a logging mode. In the logging mode, the method further includes obtaining, by the processing module, a log command. In response to the log command, the method further includes obtaining, by the processing module, a measure of an environmental condition. The method further includes storing the measure of the environmental condition in memory of the data logging device.

Abstract: A method includes receiving, by an RF receiving circuit of a passive wireless sensor of a wireless communication system, an RF signal. When a sensing element of the passive wireless sensor is exposed to an environmental condition, the method further includes affecting, by the sensing element, resonant frequency of the RF receiving circuit. The method further includes determining, by a processing module of the passive wireless sensor, a first value for an adjustable element for a known environmental condition, determining a second value for the adjustable element for an unknown environmental condition, determining a difference between the first and second values that correspond to a change, generating a coded value representative of the change, and transmitting the coded value. The method further includes receiving, by a second processing module of a sensor computing device of the wireless communication system, the coded value and determining a sensed environmental condition.

Abstract: A wireless sensor includes a radio frequency (RF) front end and a sensing integrated circuit (IC). The RF front end includes an antenna that is operable to transceive RF signals and a tuning circuit. The sensing IC includes a power supply. The sensing IC is operable to detect an impedance change of the power supply. The sensing IC is further operable to convert the impedance change into a digital value. The sensing IC is further operable to output, via the antenna, the digital value.

Abstract: A method includes receiving, by a radio frequency identification (RFID) tag, a radio frequency (RF) signal from an RFID reader. When the RF signal includes a command, the method further includes interpreting, by the RFID tag, the command to determine a field strength shell of interest. When the RFID tag is in the field strength shell of interest, the method further includes further interpreting, by the RFID tag, the command to determine a type of request, and providing, by the RFID tag, a response regarding the type of request to include one or more of a matched impedance value generated in response to the RF signal, a field strength reference current generated in response to the RF signal, and a digital value representative of an environmental condition.

Abstract: A method includes receiving, by a radio frequency identification (RFID) receiver, an electromagnetic propagated radio frequency (RF) signal. The method further includes capturing, by a current field strength detector circuit, a first current response of the tuning circuit to received signal strength of the RF signal; varying, by a tuning circuit, the variable capacitor in a first tuning direction; capturing, by the current field strength detector circuit, a second current response of the tuning circuit to the received signal strength of the RF signal; and comparing, by the current field strength detector circuit, the captured first response to the captured second response. When the captured second response is weaker than the captured first response, the method further includes varying, by the tuning circuit, the variable capacitor in a second tuning direction, and adjusting the variable capacitor in the second tuning direction until a substantially maximum received signal strength is reached.

Abstract: A radio frequency identification (RFID) tag includes a power harvesting circuit that operates generate power for the RFID tag from a continuous wave of a radio frequency (RF) signal. The RFID tag further includes a tuning circuit that is tuned based on a capacitance setting, where the capacitance setting is indicative of a power level of the power. The RFID tag further includes a processing module operably coupled to the tuning circuit, where the processing module operates to generate the capacitance setting to obtain a desired power level for the power.

Abstract: A passive wireless temperature sensor includes a radio frequency (RF) front end having a variable input impedance. The RF front end includes an antenna operable to receive an RF signal having a particular carrier frequency and a tuning circuit having a resonant frequency corresponding to the particular carrier frequency. The passive wireless temperature sensor further includes one or more temperature sensing elements coupled to the RF front end. When sensing a temperature, the one or more temperature sensing elements cause a change in the variable input impedance. The passive wireless temperature sensor further includes a processing module operably coupled to the RF front end operable to adjust the resonant frequency of the tuning circuit to compensate for the change in the variable input impedance and generate a coded value representative of the change. The coded value representative of the change corresponds to the sensed temperature.

Abstract: A radio frequency identification (RFID) tag includes a power harvesting circuit that operates generate power for the RFID tag from a continuous wave of a radio frequency (RF) signal. The RFID tag further includes a tuning circuit that is tuned based on a capacitance setting, where the capacitance setting is indicative of a power level of the power. The RFID tag further includes a processing module operably coupled to the tuning circuit, where the processing module operates to generate the capacitance setting to obtain a desired power level for the power.

Abstract: A radio frequency identification (RFID) tag includes a power harvesting circuit that operates generate power for the RFID tag from a continuous wave of a radio frequency (RF) signal. The RFID tag further includes a tuning circuit that is tuned based on a capacitance setting, where the capacitance setting is indicative of a power level of the power. The RFID tag further includes a processing module operably coupled to the tuning circuit, where the processing module operates to generate the capacitance setting to obtain a desired power level for the power.

Abstract: A radio frequency (RF) circuit includes a tank circuit having a selectively variable impedance. The RF circuit further includes a tuning circuit adapted to dynamically vary the impedance of the tank circuit, and to develop a first quantized value representative of a change to impedance of the tank circuit. The RF circuit further includes a detector circuit adapted to develop a second quantized value representative of a field strength of a received RF signal.

Abstract: A method includes receiving, by a radio frequency identification (RFID) tag, a radio frequency (RF) signal from an RFID reader. When the RF signal includes a command, the method further includes interpreting, by the RFID tag, the command to determine a field strength shell of interest. When the RFID tag is in the field strength shell of interest, the method further includes further interpreting, by the RFID tag, the command to determine a type of request, and providing, by the RFID tag, a response regarding the type of request to include one or more of a matched impedance value generated in response to the RF signal, a field strength reference current generated in response to the RF signal, and a digital value representative of an environmental condition.

Abstract: A method includes determining, by a processing module of a data logging device, whether an event has occurred that potentially compromises reliability of the data logging device. The method further includes, when the event has occurred, determining, by the processing module, whether the reliability of the data logging device has been compromised. The method further includes, when the reliability of the data logging device has been compromised, generating, by the processing module, a compromised indication signal. The method further includes, when the reliability of the data logging device has not been compromised, generating, by the processing module, a data integrity indication signal.

Abstract: A method includes establishing, by a data logging device, a sleep mode. The method further includes receiving, by a processing module of the data logging device, a second activation command that causes the data logging device to transition to a standby mode. The method further includes receiving, by the processing module, a third activation command that causes the data logging device to transition to a ready mode. The method further includes receiving, by the processing module, a fourth activation command that causes the data logging device to transition to a logging mode. In the logging mode, the method further includes obtaining, by the processing module, a log command. In response to the log command, the method further includes obtaining, by the processing module, a measure of an environmental condition. The method further includes storing the measure of the environmental condition in memory of the data logging device.

Abstract: A method includes obtaining, by a processing module of a data logging device, a log command. The method further includes determining, by the processing module, whether to enter a finished mode for the data logging device based on a data logging condition. When not in the finished mode and in response to the log command, the method further includes obtaining, by the processing module, a measure of an environmental condition. The method further includes determining, by the processing module, whether the measure of the environmental condition is within an expected range. When the measure of the environmental condition is not within the expected range, the method further includes generating, by the processing module, an environmental violation signal when triggered.

Abstract: A data logging device includes an activation circuit, an environmental sensor, a processing module, and an environmental indicator. The activation circuit is operably coupled to place the data logging device in a ready mode based on an activation signal. The environmental sensor is operable to sense an environmental condition associated with the data logging device in response to a log command to produce sensed data. The processing module is operably coupled to generate the log command; receive the sensed data; determine whether the sensed data triggers an environmental violation; and, when the sensed data triggers the environmental violation, generate an environmental violation signal. The environmental indicator is operably coupled to provide a visual indication of the environmental violation based the environmental violation signal.

Abstract: A method includes processing, by a processing module of a data logging device, a plurality of log commands. The processing of a log command of the plurality of log commands includes obtaining a measure of an environmental condition. The processing further includes updating a status of the environmental condition based on the measure of an environmental condition. The method further includes determining, by the processing module, the updated status of the environmental condition after the plurality of log commands have been processed. When the updated status of the environmental condition is favorable, the method further includes generating, by the processing module, a favorable environmental condition signal.

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.