US 7,773,945 B2Granted

RFID reader front end

AssigneeThingMagic, Inc.

InventorMatthew Stephen Reynolds

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Abstract

An RFID reader analog front end architecture employs multiplexed use of a single analog to digital converter in order to digitize the inphase and quadrature components of the incoming signal from the reader's receiving antenna. The Type 1 architecture includes an analog I/Q switch that controls which of the baseband signals will be digitized by a single Analog to Digital Converter. In the Type 2 architecture, the I/Q switch is moved so that it is directly adjacent to the receive mixers, requiring only one antialiasing filter block and gain block. In the Type 3 architecture, one mixer and its associated filtering chain are eliminated. The Type 4 architecture provides for selection of transmitter phase basis by means of an I/Q switch operating under control of the DSP that phase-shifts the transmitter with respect to the receiver.

Claims14

Dependent claims

A digital receiver circuit for a radio-frequency identification (RFID) tag reader comprising:

an analog receiver circuit receiving an RFID tag response to a transmitted command, the analog receiver circuit producing an inphase RFID tag response signal and a quadrature RFID tag response signal from the RFID tag response and having a first analog switch for selecting one of the inphase and quadrature signals for digitizing, wherein the first analog switch receives the inphase and quadrature signals from a quadrature hybrid and provides the inphase and quadrature signals to a single receiver mixer;
a single analog-to-digital converter connected via the first analog switch to the analog receiver circuit for digitizing the selected one of the inphase RFID tag response signal and the quadrature RFID tag response signal received from the analog receiver circuit;
a digital signal processor for decoding digitized RFID tag response signals from the analog-to-digital converter, determining whether the digitized RFID tag response signals decode correctly and if the digitized RFID tag signals do not decode correctly with the analog switch in a first switch state, switching the analog switch from the first switch state to a second switch state;
and
a second analog switch for receiving the inphase and quadrature signals from the quadrature hybrid and controlling the provision of the signals via a transmitter to the receiver mixer.

2 more elements

A method for converting received RFID tag response signals to digital signals, comprising the steps of:

receiving, by an analog receiver circuit, an RFID tag response signal from an RFID tag;
producing an inphase RFID tag response signal and a quadrature RFID tag response signal from the received RFID tag response signal;
selecting, by an analog switch, one of the inphase RFID tag response signal and the quadrature RFID tag response signal for digitizing;
digitizing, by an analog-to-digital converter, the selected one of the inphase RFID tag response signal and the quadrature RFID tag response signal;
decoding the digitized RFID tag response signal;
determining whether the digitized RFID tag response signal decoded correctly;
and
if the digitized RFID tag signals do not decode correctly with the analog switch in a first switch state, switching the analog switch from the first switch state to a second switch state;
transmitting a command to the RFID tag;
receiving, by an analog receiver circuit, an RFID tag response to the transmitted command;
producing an inphase RFID tag response signal and a quadrature RFID tag response signal from the received RFID tag response to the transmitted command;
digitizing, by the analog-to-digital converter, one of the inphase RFID tag response signal and the quadrature RFID tag response signal selected with the analog switch in the second switch state;
decoding the digitized RFID tag response signal;
determining whether the digitized RFID tag response signal decodes correctly;
if the digitized RFID tag signal decodes correctly, sending the decoded data for further processing;
and
if the digitized RFID tag signal does not decode correctly, reporting a decode failure.

14 more elements

Dependencies are inferred from the claim text.