Electronic Design

UHF RFID Chip Extends Reading Range To 10 Meters

The meteoric rise of radio-frequency identification (RFID) technology has drastically improved the way products and materials are inventoried, tracked, shipped, and located, as well as how people are billed. It's also changing the methods of implementing supply-chain and logistics systems. And, Atmel's ATA5590 is sure to expand these applications.

RFID is essentially the electronic version of the ubiquitous bar code. When interrogated by an external but nearby transmitter, the RFID tag powers up and transmits a unique identification code back to a receiver on the interrogation unit.

Small "passive" tags don't contain any power source (versus larger, high-priced "active" tags with batteries). These passive tags derive their operating power from the external RF signal, which is rectified and filtered into dc that powers the chip. Because power is very low, reading the code usually requires a passive tag to be within inches of the transmitter.

While this close-read range adds security for applications like key fobs and access control, the higher cost of "active" tags that allow longer read ranges has been a key reason RFID has not been implemented more quickly.

Addressing that problem, the ATA5590 chip operates in the 800-MHz to 1-GHz range and can achieve a range up to about 10 meters depending upon the interrogation device. Also called TAGIDU, the device contains 1344 bits of EEPROM, 1024 bits of user memory for the electronic product code, and 320 bits of system memory.

The tag code is programmable from the interrogator. The forward interrogator to the tag can use either amplitude-shift keying (ASK) or double-sideband (DSB) modulation. The tag to interrogator modulation may be ASK or phase-shift keying (PSK), depending on the desired operation range, bit rate, and security mechanism. The data-rate range is 5 to 80 kbits/s.

The device can achieve a 10-meter range with an interrogator equivalent isotropic radiated power (EIRP) of 4 W. Range is less than 4 meters with an EIRP of 500 mW. An anticollision function enables the operation of multiple tags within the field range for the reader. It can distinguish between up to 460 tags per second. Total tag power consumption is only 10 µW.

The TAGIDU is delivered as a die-on-wafer, but units packaged in TSSOP10 housings are available for engineering prototyping. The device costs $0.46 in 10,000-unit lots.

Atmel Corp.

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