Abstract: RFID readers, reader systems, and methods are provided that utilize double conversion for received tag response signals. A digitized signal is derived from the tag response signal by first shifting the response signal to about DC. The components of the digitized signal are then up converted and down converted and filtered such that only components around DC remain. The up converted and down converted signals may then be compared and one selected or the two combined after weighting to enhance demodulation and reduce circuit complexity.

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.

Abstract: RFID system components, such as readers and tags, communicate by a reader transmitting waveforms that encode a calibration symbol and a divide ratio. Tags include a processor to determine a backscatter link period result by dividing a count value representing the calibration symbol by the divide ratio and adding an adjustment. Tags modulate a backscatter waveform that includes symbols using a link period determined from the result.

Abstract: Systems and methods to determine timebase and timing (i.e., time sync) of received signals in RFID systems. Multiple matched filters corresponding to multiple timebases are used to receive the preambles of signals received from RFID tags. The multiple matched filters define a range of expected timebases of the received signals. The matched filter with the maximum output signal peak is used to derive the timebase and timing of the received signal. Viterbi techniques can be used in determining the timebase and timing to incorporate a portion of the data signal in addition to the preamble. Reconfigurable matched filters can be used so that after a preliminary timebase is determined as described above, the matched filters can be reconfigured to define a new smaller range centered about the preliminary timebase. This allows the timebase to be determined with finer resolution when another preamble portion is received.

Abstract: A transmitter shifts a baseband data signal having a bandwidth of 2?M using a tone signal having a frequency ?M, which centers a sideband of the data signal at zero frequency. The transmitter then filters the shifted signal to filter out the non-centered sideband, and then adds the tone signal to form a composite signal. The transmitter upconverts the composite signal during a first operational mode using a RF signal having a frequency ?C equal to a center frequency of a channel. In a second operational mode, the transmitter upconverts a DC level using the same RF signal. The upconverted DC level can be used as a continuous wave carrier signal having a frequency ?C. The transmitter has a single RF oscillator to output both a SSB signal centered at frequency ?C during the first mode and a carrier signal of frequency ?C during the second mode.

Abstract: An RFID tag has a fuse that is adapted to store configuration data in a way that survives loss of power. The fuse can be one time programmable or many times programmable, and be implemented with a non-volatile memory. The configuration data becomes available to an operational component of the tag, such as at power up, controlling its performance.

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 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: A transmitter upconverts a SSB data signal during a first operational mode using a RF upconverting signal having a frequency that is offset from a center frequency of a channel (?C) by an amount that depends on the data signal's SSB bandwidth (?M). In a second operational mode, the transmitter upconverts a tone signal having a frequency ?M using the same RF upconverting signal. The upconverted tone signal can be used as a continuous wave (CW) carrier signal having a frequency ?C. The transmitter has a single RF oscillator to output both a SSB signal centered at frequency ?C during the first mode and a carrier signal of frequency ?C during the second mode.