A wireless communication system includes a plurality of wireless sensors. A wireless sensor includes a radio frequency (RF) receiving circuit, and a sensing element, where the sensing element affects the resonant frequency of the RF receiving circuit. The wireless sensor further includes a processing module operable to determine a first value for an adjustable element of a plurality of elements for a known environmental condition, a second value for the adjustable element for an unknown environmental condition, a difference between the first and second values that corresponds to a change, and to generate a coded value representative of the change. The wireless communication system further includes one or more sensor computing devices coupled to the plurality of wireless sensors via a network. A sensor computing device includes a second processing module operable to receive the coded value and determine a sensed environmental condition based on the coded value.

An operation of calibrating the object using a reference reader is performed, the calibration operation including an operation of placing the reference reader at various distances away from the object that correspond to various values of a parameter within the object that is representative of the intensity of the signal received by the object, and, for each distance, an operation of determining an internal phase-shift compensation in the object with respect to a nominal internal phase shift, making it possible to obtain a load modulation amplitude that is higher, in terms of absolute value, than a threshold, and an operation of storing a lookup table of the various values of the parameter and the corresponding internal phase-shift compensations.

A wireless tag processing device includes a wireless tag reader-writer and a processor configured to acquire first and second sets of parameter values, control the reader-writer to transmit a radio wave using each parameter value of the first set and acquire a first intensity of a response wave from a wireless tag, when a highest first intensity satisfies a first condition, determine a parameter value of the first set corresponding to the highest intensity as a parameter value to be used by the reader-writer, and when the highest intensity does not satisfy the condition, control the reader-writer to transmit a radio wave using each parameter value of the second set and acquire a second intensity, and when a highest second intensity satisfies a second condition, determine a parameter value of the second set corresponding to the highest second intensity as the parameter value to be used by the reader-writer.

An operation of calibrating the object using a reference reader is performed, the calibration operation including an operation of placing the reference reader at various distances away from the object that correspond to various values of a parameter within the object that is representative of the intensity of the signal received by the object, and, for each distance, an operation of determining an internal phase-shift compensation in the object with respect to a nominal internal phase shift, making it possible to obtain a load modulation amplitude that is higher, in terms of absolute value, than a threshold, and an operation of storing a lookup table of the various values of the parameter and the corresponding internal phase-shift compensations.

A wearable device, such as a finger ring worn by a user, communicates information about a user to a reader that uses the information in order to perform a transaction. Such wearable device may be conveniently carried by and accessible to the user such that utilization of the device for the transaction is less burdensome for the user, thereby encouraging use of the device for particular transactions. Indeed, in some cases, such as when the device is implemented as a finger ring or other type of jewelry, the user may be encouraged to carry the device in an exposed manner such that it is readily available for the transaction without the user having to search in a wallet, pocket, or purse for the device.

A radiofrequency harvester circuit may be used in a battery-less RFID device. The harvester circuit includes an antenna unit that captures radiofrequency signals and harvesting circuitry coupled to the antenna unit for collecting energy from the radiofrequency signals captured by the antenna unit. The antenna unit is selectively tunable at a plurality of tuning bands that are scanned by selectively tuning the antenna unit at different frequency bands and sensing respective values indicative of the power of radiofrequency signals captured by the antenna unit at the frequency bands scanned. A highest value out of said respective values for the power of radiofrequency signals as well as the frequency band in the plurality of tuning bands of the antenna unit providing the aforesaid highest value are identified and the harvester circuit is operated with the antenna unit tuned at the frequency band providing the highest value thus identified.

In accordance with a first aspect of the present disclosure, a near field communication (NFC) device is provided, comprising: a modulator configured to modulate a carrier signal received from an external reader, resulting in a modulated carrier signal; a controller configured to control a transmission of the modulated carrier signal to the external reader; a transmitter driver configured to transmit said modulated carrier signal, said transmitter driver having a variable resistance; wherein the controller is further configured to change said variable resistance during a modulation phase of the NFC device such that a clock synchronization window is widened. In accordance with a second aspect of the present disclosure, a corresponding method of operating an NFC device is conceived. In accordance with a third aspect of the present disclosure, a non-transitory machine-readable medium is provided, comprising instructions which, when executed, carry out a method of the kind set forth.

Methods, systems, and devices for wireless communications are described. Generally, the described techniques provide for identifying, by a wearable device, a baseline antenna impedance value, detecting one or more sensor inputs, monitoring for a variation in antenna impedance from the baseline antenna impedance value, identifying a user gesture (e.g., based at least in part on the detected sensor inputs and the variation from the baseline antenna impedance value) at least one user gesture, and updating an operational status of the device based on the detected user gesture.

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.

An RFID IC may operate at a relatively low clock frequency while impedance matching to an antenna is being tuned to increase the amount of power that the IC can extract from an incident RF wave. A tuning circuit tunes the impedance matching by adjusting a variable impedance coupling the IC and the antenna. The IC may power-up with a low clock frequency or reduce its current clock frequency to a lower clock frequency prior to tuning or during the tuning process, and may increase its clock frequency upon completion of tuning or during the tuning process.