Abstract: RFID systems, devices, software and methods are adapted for receiving from an RFID tag at least waves that communicate at least a first version of its code. An output tag code is output that is the same as the first version, if a fidelity criterion is met regarding the first version. If not met, the output tag code is instead a final version that is reconstructed from the first version, and also from any additionally optionally subsequently received versions. In some embodiments, an error recovery block includes a subcomponent fidelity criterion checking block that can determine whether the fidelity criterion is met, and a code reconstruction block that can derive the final version.

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: RFID readers, systems, and methods are provided for overcoming the effects of RF interference. While a system is communicating in a channel, RF interference is monitored. If it is low, then the next channel to be hopped onto is chosen in an unbiased manner. But if interference is high, then the next channel to be hopped onto is chosen in a biased manner that disfavors at least one channel over another, in view of the detected interference. The choice of the next channel can thus result in diminishing communication in channels with a lot of RF interference.

Abstract: RFID readers, systems, and methods are provided for overcoming the effects of RF interference. While a system is communicating in a channel, RF interference is monitored. If it is low, then hopping to another channel is performed according to an ordinary decision. But if interference is high, then hopping out to another channel can be earlier than would be dictated by the ordinary decision under the same circumstances. The earlier hopping out can result in diminishing communication in channels with a lot of RF interference.

Abstract: Methods and apparatus provide secure two-way (reader-to-tag and tag-to-reader) RFID communications. According to one aspect, a tag receives a noise-encrypted RF carrier signal from a reader and backscatter modulates it with tag information. Eavesdroppers cannot extract the tag information from the backscattered signal because it is masked by the noise encryption.

Abstract: RFID system components, such as readers and tags, communicate where at least a portion of data or a password is transmitted in encrypted form. The reader transmits a command, along with data or a password encrypted using an encryption kernel. In some instances, the tag itself has sent the kernel.

Abstract: RFID readers, RFID tags, software, and methods decode a signal received in an RFID system. From received data, a decoder determines a number of possible test series for the output. In one embodiment, the decoder uses a memory of a previous sample to derive a subsequent sample in the test series, so as to ensure that all the test series are valid. A metric is then computed for how well each test series fits the received data. The metrics are compared to select for output the test series with the best fit. In a further embodiment, at least one of the metrics is further used to determine if a collision were present.

Abstract: RFID tags are commanded to generate a pilot tone in their backscatter. When the backscattered pilot tone is received in the reader, the pilot tone is used to estimate the tag period/frequency. Then, the estimate is used to seed and lock a symbol timing recovery loop, which provides a detected signal to one or more correlators for detecting the tag preamble. A delayed version of the received tag signal is compared against a baseline signal threshold established from the received signal to detect the pilot tone.

Abstract: RFID systems, devices, software and methods are adapted for receiving from an RFID tag at least waves that communicate at least a first version of its code. An output tag code is output that is the same as the first version, if a fidelity criterion is met regarding the first version. If not met, the output tag code is instead a final version that is reconstructed from the first version, and also from any additionally optionally subsequently received versions. In some embodiments, an error recovery block includes a subcomponent fidelity criterion checking block that can determine whether the fidelity criterion is met, and a code reconstruction block that can derive the final version.

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: 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.

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.

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: RFID readers, RFID tags, software, and methods decode a signal received in an RFID system. From received data, a decoder determines a number of possible test series for the output. In one embodiment, the decoder uses a memory of a previous sample to derive a subsequent sample in the test series, so as to ensure that all the test series are valid. A metric is then computed for how well each test series fits the received data. The metrics are compared to select for output the test series with the best fit. In a further embodiment, at least one of the metrics is further used to determine if a collision were present.

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: 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: Methods of and apparatuses for optimizing quantization noise cancellation in multi-phase sampled MASH ADCs are disclosed. A test signal is combined with quantization noise produced by a delta-sigma modulator. Two parallel adaptive filters (i.e. even and odd filters) are configured to receive respective even and odd samples of a digital output signal of a MASH ADC analog modulator. Adaptive coefficients for the even adaptive filter are derived from correlation results between the even samples of the test signal and associated even samples of the final digital output signal. Similarly, adaptive coefficients for the odd adaptive filter are derived from correlation results between the odd samples of the test signal and associated odd samples of the final digital output signal. Using the adaptive coefficients, the even and odd adaptive filters are able to independently compensate for analog variations in the two paths.

Abstract: Methods and apparatus for providing secure two-way (reader-to-tag and tag-to-reader) RFID communications. According to one aspect of the invention, a tag receives a noise-encrypted RF carrier signal from a reader and backscatter modulates it with tag information. Eavesdroppers cannot extract the tag information from the backscattered signal because it is masked by the noise encryption. According to another aspect of the invention, establishing a secure two-way RFID communication link includes a reader modulating a carrier signal with a noise encryption signal and broadcasting the noise-encrypted carrier to a singulated tag. The tag backscatter modulates the noise-encrypted carrier with a first portion of a key and/or a one-time pad pseudorandom number.

Abstract: A symmetrical communication protocol allows handsets to operate as a master unit or a slave unit and operate independently of any base station. Remote units may contact each other directly with the calling unit being temporarily designated as a master unit and the called unit being designated temporarily as a slave unit. A wireless communication link is established between the two units and the units frequency-hop in synchronization in accordance with FCC requirements. The units independently monitor the signal strength of the incoming signal and can transmit power change commands to the other unit to increase or decrease transmission power as required. A calling unit initially transmits a call request on a limited number of the available frequency channels in order to decrease the acquisition time period. An idle unit has a sleep cycle and an awake cycle.