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Operational Description
3M Compact RFID Reader 1000
This RF field from the reader can range from 6 inches to 30 feet, depending on
the antenna port power and antenna gain.
The RF field generated by the reader performs the following:
Energize the tag antenna to provide power to the integrated circuit
Provide a synchronized clock source for the tag
Act as a carrier for returned tag data
The reader can be configured to constantly generate its frequency-hopping tag
interrogation RF signal but in many applications, to minimize radio interference,
the reader’s transmitter is idle until an event triggers the reader to begin
transmission. While the RF signal is transmitted, the reader is monitoring the
receiver output for modulation indicating the presence of a tag.
When a tag enters the RF field, its antenna is energized and the tag starts to
divide down the carrier, demodulate commands from the reader, and begins to
clock data to its antenna modulator circuit. The modulator circuit shunts the
antenna element, causing momentary fluctuations in the carrier amplitude
reflected back to the reader. The reader detects this amplitude-modulated data
and decodes the resulting bit stream into the actual tag data. The decoding
scheme depends on the specific tag protocol.
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3M Compact RFID Reader 1000 Architecture
The 1000 reader contains a Transmitter section, Receiver section, Synthesizer
section, and Digital Modem.
The Transmitter section contains a digital-to-analog converter (DAC), I-Q
modulator, filtering, RF power amplifier and the antenna multiplexer circuit.
Communication with RFID tags is 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 low noise amplifiers, 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.