Abstract: An RFID tag that receives a calibration instruction from a reader can determine the basic backscatter period of the symbols to be backscattered. According to some embodiments, when the instruction includes a calibration feature that is to be divided by a divide ratio, the tag measures the duration of the feature in terms of numbers of internal pulses, resulting in a binary L-number. Then at least two versions of the L-number (PR1-number, PR2-number) are combined, so as to yield the effective result of the division alternately, even when the divide ratio is a non-integer. The backscatter period can then be determined from the BP-number and the period of the internal pulses.

Abstract: RFID system components, such as readers and tags, communicate where the reader inventories a population of tags. The reader evaluates responses from tags by categorizing them in slots. As tags are inventoried, the number of slots based on a Q-parameter is reduced. The reader reduces the Q-parameter first in a first manner, then in a second manner where the second manner is different from the first manner. The first manner and the second manner may be different algorithms, different subroutines of an algorithm, or the same damping algorithm with different damping parameters.

Abstract: RFID system components, such as readers and tags, communicate where the reader inventories a population of tags. The reader evaluates responses from tags by categorizing them in slots. As tags are inventoried, the number of slots based on a Q-parameter is reduced. The reader determines an interim value for the Q parameter, generates a Q1 value by applying the interim value to a damping function, and uses the Q1 value in another round of interrogation. The reader then determines whether to increase or decrease the interim value depending on the tag replies. The increase or decrease may be an increment or a decrement such as incrementing or decrementing a floating point number of the interim value in a damping function that is arranged to return an integer by rounding the floating point number.

Abstract: A circuit for an RFID tag has at least two RF ports for driving points of the antenna that may correspond to different RF polarizations. The RF ports may be driven by a common modulating signal, or by separate modulating signals. Further, the ports may be coupled and uncoupled together, responsive to a control signal. The control signal may be the same as one or both of the modulating signals.

Abstract: RFID readers exchange information with RFID tags. The information is encoded for transmission and decoded upon reception. Encoding is in binary bits, which are in turn encoded in waveform segments. The last transmitted waveform incorporates an ending-triggering transition, and terminates in a preset manner with respect to when the ending-triggering transition occurs. Parsing while decoding can happen by waiting for the ending-triggering transition, and then waiting according to the preset manner. This way there is no ambiguity in the ending of the waveform, and no End Frame is necessary.

Abstract: An RFID reader inventories a population of tags. The reader evaluates responses from tags by categorizing them in slots. As tags are inventoried, the number of slots based on a Q-parameter is reduced. The reader addresses the tags by communicating a Q1 value for the Q parameter, generates first contents from replies received from the tags, and computes a first merit statistic based on the first contents. Then, the reader repeats the process with a Q2 value. Upon computing the first and the second merit statistics, the reader determines a Q3 value for the Q parameter. If the Q3 value is substantially equal to the Q1 value, the reader continues to receive the second replies without communicating the Q3 value. If the Q3 value is different from the Q2 value, the reader uses the Q3 value for another round of iteration heuristically converging on an optimum Q value.

Abstract: RFID system components, such as readers and tags, communicate where the reader inventories a population of tags. The tags choose randomly one of a plurality of slots in response to each one of the values communicated by the reader and reply according to their chosen slot. The reader may initiate the inventorying by determining a Q-parameter value from a stored value and communicating the Q-parameter value to the tags. The reader may evaluate replies received from the tags in another plurality of tags, determine a second value from evaluating the second replies, and store the second value for future use.

Abstract: An RFID reader inventories a population of tags. The reader evaluates responses from tags by categorizing them in slots. As tags are inventoried, the number of slots based on a Q-parameter is reduced. The reader addresses the tags by communicating a Q1 value for the Q parameter, generates first contents from replies received from the tags, and computes a first merit statistic based on the first contents. Next, the reader determines a Q2 value for the Q parameter, which if used in the same way would meet a preset fairway condition better than the first merit statistic. After determining the Q2 value, the reader addresses a portion of the tags by communicating the Q2 value for the Q parameter.

Abstract: RFID system components, such as readers and tags, communicate by transmitting and receiving a wave that conveys a bit stream. Informing signals, such as special bits, are inserted in the stream between words. An informing signal indicates whether a certain word is the last word in the stream or not.

Abstract: A process is disclosed for exchanging data between one or more RFID tags and an interrogation unit comprising transmitting a burst of data from the one or more RFID tags.

Abstract: A process is disclosed for communicating with individual tags in a population of tags having a binary tree organization, wherein each tag corresponds to a leaf node of the binary tree. The process includes singulating a predetermined leaf node and returning to a designated re-entry node associated with the predetermined leaf node after singulating.

Abstract: According to one aspect of the present invention, there is provided a method of calibrating an oscillator within a radio-frequency identification (RFID) circuit for use in an RFID tag. A plurality of calibration values is stored within a memory structure associated with the RFID circuit. Each of the calibration values corresponds to a respective oscillation frequency of the oscillator. A selected calibration value is selected from the plurality of calibration values stored within the memory structure, according to a first selection criterion. The oscillator is then calibrated in accordance with the selected calibration value.

Abstract: Rewriteable electronic fuses include latches and/or logic gates coupled to one or more nonvolatile memory elements. The nonvolatile memory elements are configured to be programmed to memory values capable of causing associated electronic circuits to settle to predetermined states as power-up or reset signals are applied to the fuses. Although not required, the nonvolatile memory elements used in the rewriteable electronic fuses may comprise floating-gate transistors. An amount of charge stored on the floating gate of a given floating-gate transistor determines the memory value and, consequently, the state to which a fuse settles upon power-up or reset of the fuse.

Abstract: RFID readers transmit data to query tags at one or more data rates. Before transmitting data, the RFID readers also transmit special preambles that inform of the data rate that will be used for transmitting the data. The preambles have a call aspect and a rate aspect. The rate aspect has a feature substantially determined from a rate selected for transmitting the data. The feature may encode the rate indirectly or explicitly. The call aspect may be implemented by call transitions that define a timing, whose duration is independent of the selected rate. The duration may be advantageously set according to an assumed state of the RFID tag bandwidth filter. Therefore an RFID tag may use the call aspect of the preamble to prepare itself for receiving data, and the rate aspect to determine its rate of transmission for setting its filter bandwidth accordingly.

Abstract: A radio frequency identification tag is disclosed that is configured to transmit a signal modulated with one of more than two different subcarrier modulation frequencies such that the signal represents more than one binary bit as a single symbol.

Abstract: In accordance with one aspect of the present invention, there is provided a method of calibrating an oscillator within a radio-frequency identification (RFID) circuit for use in an RFID tag. The oscillator has an oscillation frequency. A calibration value is stored within a non-volatile memory associated with the RFID circuit. The oscillator is calibrated in accordance with the calibration value. The storing of the calibration value includes recovering a reference frequency from a test signal supplied to the RFID circuit, calculating the calibration value to correspond to a difference between the recovered reference frequency and the oscillator frequency, and writing the calibration value to the non-volatile memory.

Abstract: According to one aspect of the present invention, there is provided a method to backscatter modulate a first radio-frequency (RF) signal from a radio-frequency identification (RFID) tag. An oscillator calibration value is retrieved from a non-volatile memory associated with the RFID tag. An oscillation frequency signal is generated within the RFID tag, the generating of the oscillation signal being performed utilizing the oscillator calibration value. A command signal is generated within the RFID tag, the command signal being based on command data received at the RFID tag in a second radio-frequency signal from an RFID reader. The first radio-frequency signal is backscatter modulated in accordance with both the oscillation frequency signal and the command signal.

Abstract: RFID tags, tag circuits, and methods adapting the reception bandwidth. A tag has a decoder for decoding a first received wireless signal subject to a reception bandwidth setting. The tag also has a selector switch for transitioning to a different setting, such as by switching to using a different filter. A subsequently received second signal is decoded subject to the new reception bandwidth setting.

Abstract: According to one aspect of the present invention, there is provided a method of calibrating an oscillator within a radio-frequency identification (RFID) circuit for use in an RFID tag. A first calibration value is stored within a non-volatile memory associated with the RFID circuit. The oscillator is calibrated in accordance with the first calibration value. The storing of the first calibration value is performed responsive to receiving a calibration command and an associated update value at the RFID circuit.

Abstract: RFID readers transmit data to query RFID tags. Before transmitting the data, the RFID readers also transmit special preambles that inform of parameters of communication that are to be used. RFID tags decode the preamble, and adjust accordingly to optimize the communication. The preambles of the invention start with a delimiter that has a substantially constant duration regardless of the communication parameters that will be used, such as transmission data rate.