Cambridge Enterprise Limited

Sithamparanathan Sabesan

Ian H White

Michael Crisp

Richard Penty

Zhe Fu

Ian Professor White

A system for the distribution of RFID signals to a remote antenna or a remote antenna network comprising: a central control module to generate signals and control the protocol operations; cable, in particular twisted pair cable, connecting the central module to one or more antenna subsystems carrying substantially baseband representations of the reader to tag modulation and tag to reader modulation.

RFID systems

We describe an RFID tag reading system comprising a plurality of transmit/receive antennas to provide spatial transmit/receive signal diversity, and a tag signal decoder. The system combines received RF signals from the antennas, and the antennas are spaced apart from one another sufficiently for one said antenna not to be within the near field of another. The system performs a tag inventory cycle comprising a plurality of tag read rounds, each having a set of time slots during which a said tag is able to transmit tag data including a tag ID. The system is configured to perform, during a tag inventory cycle, one or both of: a change in a frequency of the tag interrogation signals transmitted simultaneously from the plurality of antennas, and a change in a relative phase of a the RF tag interrogation signal transmitted from one of the antennas with respect to another.

RFID tag interrogation systems

We describe a methods of locating an RFID tag. One method transmits tag location signals at a plurality of different frequencies from a plurality of different antennas spaced apart by more than a near field limit distance. The processing determines a phase difference at the plurality of different frequencies by determining a phase difference between either i) two or more of the transmit signals resulting in a maxima in the returned signal RSSI or ii) a first transmit signal and its corresponding return signal. The range determining uses return signals weighted by signal strength. Further data which may be used for averaging may be generated by using the above techniques along with changes in the polarisation state of the transmit and receive antennas and/or physical reconfiguration of the antennas (e.g. switch the transmit and receive elements).

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Middlesex, United Kingdom

Sithamparanathan Sabesan