An information collection system includes a plurality of radio tags and a reading device. Each of the radio tags stores identification information and includes a sensor, an antenna that receives a carrier wave from the reading device, and a data transmission unit that sends measurement data including the identification information and information obtained by the sensor to the reading device after the carrier wave is received by the antenna. The plurality of radio tags send the identification information and the information obtained by the sensor with different natural periods from the data transmission units. The reading device transmits the carrier wave to each of the radio tags, receives data from each of the radio tags, and obtains the data.

A system is provided that can automatically adjust a tuned circuit to resonate at the frequency of an applied excitation signal. The error in the resonant frequency of the tuned circuit is determined in real time from signals derived from within the network. The system permits the use of a time varying excitation frequency in a high Q circuit, including modulation conveying information. The tuning information may be stored in a memory and used to set the tuning instantaneously in order to maintain resonance when the excitation frequency changes abruptly, for example when frequency shift keying is used.

A near field communication (NFC) or Radio Frequency Identification (RFID) reader device for contact-less communication includes a transmitter block connected to an antenna via a matching circuitry. An electromagnetic carrier signal and modulated data information are emitted via this main antenna. Any secondary object brought into the vicinity of the main antenna influences the primary resonant circuit resulting in a load change seen by the transmitter. This detuning can cause increased power consumption, RF (Radio Frequency) standard incompliance, and device damage. The present disclosure describes devices and methods on how to detect detuning and how to regulate the transmitter's output.

A wireless sensor includes a radio frequency (RF) receiving circuit including a plurality of components, where impedances of the plurality of components establish a resonant frequency of the RF receiving circuit. The wireless sensor further includes a sensing element that when exposed to an environmental condition, affects the resonant frequency of the RF receiving circuit. The wireless sensor further includes a processing module that is operable to determine a first value for an adjustable element of a plurality of elements for a known environmental condition based on the resonant frequency and the carrier frequency, determine a second value for the adjustable element for an unknown environmental condition 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 environmental condition and the unknown environmental condition.

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.

An NFC (near field communication) device can include a resonance unit and an NFC chip. The resonance unit may communicate with an external device through an electromagnetic wave. The NFC chip can provide output data to the resonance unit, receive input data from the resonance unit, and can reduce a Q factor (quality factor) of the resonance unit when a signal receive operation is performed in a card mode, and can maintain the Q factor of the resonance unit in a reader mode and when a signal transmit operation is performed in the card mode.

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.

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 system in which at least one of the RFID tag antenna and the RFID reader antenna has an impedance matching network associated therewith in order to better match the impedances of the two antennas. This impedance matching places the antennas into an over-coupled regime once they are within a reasonable distance of each other (e.g., 2 to 50 mm). It also increases the Q-factor of the improved antenna, which can greatly increase the range at which the RFID reader can read the RFID tag. This improved RFID system may be used in any of a variety of application, including operating a door lock mechanism.

A NFC object reader's NFC antenna system configured to dynamically change an element of the NFC antenna system to maintain the NFC antenna system's antenna default resonant frequency. The NFC antenna system can be configured to include a tuning subsystem, integrated with sensors to trigger tuning of NFC antenna system's antenna.