User's Manual

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accomplished using a half-duplex signal consisting of a modulated reader signal followed by a

Continuous Wave (CW) signal. The modulated signal sends data to the tag. The tag decodes this

signal and then Backscatters (uplinks) its data during the CW portion of the cycle. The

Transmitter (downlink) modulation used for communication with RFID tags is Double Sideband

Amplitude Shift Keying (DSB-ASK) or Phase Reversal Amplitude Shift Keying (PR-ASK), depending

on tag type and reader operating mode. Data rates range from 40 to 160 kbps.

The Receiver section contains I-Q demodulator, filtering and an analog-to-digital (ADC)

converter. The Receiver architecture is direct conversion, and therefore it operates using the

same Local Oscillator (LO) frequency and RF channel used by the Transmitter. During the

Backscatter (uplink) portion of the tag communication cycle the Receiver down-converts the

modulation data from the tag to baseband, where it is amplified and low pass filtered before

being converted to a digital signal by the ADC converter. The receiver accommodates tag

Backscatter data rates range from 32 to 640 kbps, depending on tag type and reader operating

mode.

The Synthesizer section contains a voltage-controlled oscillator (VCO) and phase-locked loop.

The Synthesizer generates a Local Oscillator (LO) signal that is shared with the Transmitter and

Receiver sections. The VCO operating frequency is constrained under software control to the

902 to 928 MHz UHF ISM band when configured for the FCC region.

The Digital Modem includes the DSP, dual-function ADC-DAC converter, and general purpose

input/output communication interfaces. The Digital Modem has direct control over transceiver

functions, including operating frequency, TX power control, and generation and decoding of

baseband digital modulation data sent and received by the reader for RFID tag read and write

operations.

The Host interface section includes a microprocessor, its associated memory, and all of the

circuitry needed to implement the Ethernet interface. The host processor serves as the

interface between the radio and the outside world.