What is described is an Radio Frequency Identification (RFID) tag configured for communicating with an Radio Frequency Identification (RFID) reader, wherein the RFID tag is configured to receive a query command from the RFID reader, to measure a duration of a TRcal signal comprised by the query command, and to determine an individual Backscatter Link Frequency for communicating with the RFID reader based on the measured duration of the TRcal signal. The invention also refers to an RFID reader and to a corresponding method.

In an RFID system having at least one tag and at least one reader, a tag and a reader can, in one embodiment, use a pair of keys, known to both the tag and the reader, to restrict the interaction of the tag and the reader so that tags having the pair of keys interact only with readers that use the pair of keys.

Systems and methods for radio-frequency identification (RFID) tag communication are provided. One radio-frequency identification (RFID) tag includes a communication device configured to communicate with an RFID reader and an impedance element configured to change an variable impedance of the RFID tag. The RFID tag further includes at least one switch connected to the impedance element and a controller connected to the at least one switch and configured to control operation of the switch between open and closed states based on a control signal received from the RFID reader, wherein the variable impedance of the RFID tag is changed between a first modulating impedance value and a second modulating impedance value when the switch is changed between the open and closed states.

A system for cataloguing items disposed within a predefined volume;

each item of said items having associated therewith a tag;
each tag having a unique identifier;
each tag including:
a tag radio transmitter having a predefined tag transmission range
a tag radio receiver having a predefined tag reception range
a response logic device;
said system further including a tag interrogator;
said tag interrogator including:
a database
an interrogation logic device
a tag interrogator transmitter having a predefined tag interrogator transmission range
a tag interrogator radio receiver having a predefined tag interrogator reception range.

Systems and methods are provided for automatically detecting passive components in communications systems using radio frequency identification (RFID) tags. A coupling circuit is provided in a system between a communications network and an RFID tag. The RFID tag is associated with a passive element of a distributed antenna system (DAS). The coupling circuit can allow an RFID signal received from an RFID transmitter over the communications network to be transported to the RFID tag. The coupling circuit can substantially prevent mobile communication signals on the communications network from being transported to the RFID tag.

Examples described herein generally relate to a system for monitoring tags in a retail environment. The system includes an exit system including one or more radio frequency identification (RFID) readers that read a tag to obtain exit system measurements associated with a tag detection event. The system includes a memory and a processor configured to execute instructions to configuring each of a plurality of exit gates including a plurality of RFID readers with a different operating frequency than the plurality of RFID readers at an adjacent exit gate. The processor is configured to synchronize the plurality of RFID readers at each exit gate to prevent two readers at the exit gate from concurrently talking with overlapping coverage areas and a same polarization. The processor is configured to detect one or more tags within the coverage areas.

A radio-frequency identification (RFID) tag reader interrogates a passive RFID tag by transmitting a signal to the tag, then detecting a much weaker reply at the same carrier frequency from the tag. Unfortunately, self-interference caused by signal leakage within the reader or crosstalk among the reader's antenna elements can make the reply more difficult to detect and limit the range at which the reader can sense tags. A self-interference cancellation circuit in the reader reduces or suppresses the effects of signal leakage and crosstalk, enabling detection of weaker tag replies. The self-interference cancellation circuit can calibrate itself before each transmission to ensure good performance. This improves the reader's sensitivity, increases the reader's range, reduces the reader's power consumption, and/or reduces the minimum required dynamic range of the analog-to-digital converters (ADCs) that digitize the received tag replies.

Protocol-specified RFID tag inventorying can be modified to streamline information exchange. For example, RFID tags may be able to respond to certain RFID reader commands with additional or other information instead of only a pseudorandom number or a certain tag identifier, or may not even respond at all. Such other information may include all or portions of other tag identifiers, or information associated with tag identifiers, such as error-checking codes or protocol control bits. Tags may also choose data stored in tag memory with location of the data known only to the tag, compare to a mask received in an inventorying command and decide to participate or not in an inventory round based on a comparison result.

A method and RFID writer-reader for selecting a RFID data carrier from a plurality of RFID data carriers detected by an RFID writer-reader, wherein the RFID data carrier of the RFID data carriers detected in productive operation is selected based on the respective degree of correspondence between sequences of actual values determined in productive operation that are compared with at least one sequence of setpoint values so as to reliably select a desired RFID data carrier even in difficult reception situations.

Systems and methods for decoding data transmitted by RFID tags are disclosed. One embodiment of the invention includes an analyzer and equalizer configured to filter an input signal, an estimation block configured to obtain a baseband representation of the modulated data signal by mixing the filtered input signal with the carrier wave, and a coherent detector configured to perform phase and timing recovery on the modulated data signal in the presence of noise and to determine a sequence of data symbols.