An accessory device to be mounted on a main device is provided with a wireless IC device. The main device is provided with a reader/writer that is an interrogator that communicates with the wireless IC device of the accessory device. When the accessory device is mounted on or about to be mounted on the main device, the reader/writer selects two or more frequencies in a frequency band in which an authentic wireless IC device can communicate to perform communication with the wireless IC device. With this configuration, even if the identification code written in an RFID tag is read and the RFID tag is duplicated, the duplicated RFID tag can be accurately and effectively determined as being counterfeit.

A radio frequency device with mechanisms for adjustment of the impedances and frequencies of its antennas comprises a first circuit board, a radio frequency module and a second circuit board. The radio frequency module is disposed on the first circuit board that is disposed on the second circuit board. The radio frequency module comprises an antenna unit, a first frequency tuning element and a radio frequency circuitry. The antenna unit is disposed within a clearance area of the first circuit board, and connected to the radio frequency circuitry via a feeding circuit. The second circuit board comprises a second frequency tuning element that is electrically connected to the antenna unit via a ground circuit and the first frequency tuning element on the first circuit board. Thus, the resonance frequency of the antenna unit can be adjusted according to the first and the second frequency tuning element.

A near field communication (NFC) reader is disclosed. The NFC reader includes a first section. The first section includes an NFC controller and a filter coupled to the NFC controller. The filter includes a filter capacitor. The first section further includes a first tuning circuit coupled to the filter. The first tuning circuit includes a tuner capacitor that is electrically coupled in parallel to the filter capacitor. The first tuning circuit is configured and adapted to be coupled to a coaxial cable. The NFC reader also includes a second section. The second section includes a second tuning circuit. The second tuning circuit includes a second tuner capacitor and a damping resistor. The second tuning circuit is configured and adopted to be coupled to the coaxial cable. The second section further includes an antenna coupled to the second tuning circuit.

The invention relates to a device for protecting a near field communication router against possible over-voltages picked up by an antenna. The device includes two voltage-limiter elements between terminals of the antenna and a ground. A circuit detects the presence of an electromagnetic field in the vicinity of an operating frequency of the router, and controls the limiter elements, the limiter elements being active by default.

A method for detecting receivers includes a step of detecting a receiver, in which step a general controller detects an adjustable receiver when a general antenna receives a secondary wave emitted by the adjustable receiver, followed by a reconfiguration step in which the general controller commands a controller of the detected adjustable receiver to switch to an interaction mode in which the impedance of the adjustable receiver is alternated between a first configuration impedance and a second configuration impedance in order to detect other receivers. The reconfiguration step is of a duration that is an order of magnitude higher than the duration of each alternation of the first and second configuration impedances.

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.

A pressure sensing circuit for use with a wireless sensor that includes an antenna and a pressure sensing element. The antenna includes a first pole and a second pole and is operable to transceive radio frequency signals between the wireless sensor and a wireless data collecting device. The pressure sensing element includes an electrical circuit and a diaphragm. When pressure is applied to the diaphragm, a characteristic of the electrical circuit changes. The changing of the characteristic of the electrical circuit causes one or more RF characteristics of the wireless sensor to change, which is interpretable to determine a pressure being applied to the pressure sensing element.

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.

A passive radio frequency identification (RFID) sensor includes at least one antenna. The least one antenna has an antenna impedance operable to vary within an environment in which the antenna is placed. The RFID sensor further includes a processing module coupled to the antenna comprising a tuning module coupled to the antenna. The tuning module is operable to vary a reactive component impedance coupled to the antenna in order to change a system impedance, the system impedance includes the antenna impedance and the reactive component's impedance, to produce an impedance value representative of the reactive component's impedance. The RFID sensor further includes a memory module operable to store the impedance value representative of the reactive component's impedance, and a wireless communication module coupled to the processing module, operable to communicate with an RFID reader and to exchange the impedance value representative of the reactive component's impedance with the RFID reader.

A payment reader includes a tuning circuit that provides a tuned transmission source signal to an antenna for transmission. A sense circuit coupled to the antenna provides a measured transmitted signal to a binary phase detection circuit. The binary phase detection circuit filters and processes the signal to provide an analog phase signal that corresponds to a phase difference between the measured transmitted signal and the transmission source signal. A comparison circuit compares the analog phase signal to a reference signal, and a decision circuit adjusts the operation of the transmission circuitry based on the comparison.