Increasing range on RFID reader?

PJMonty

I was wondering if anyone knows of any way to increase the range of the RFID reader that Parallax sells. The current range is around 6 inches, and I am looking for something in two to three foot range. Is this possible in any way? If not, is there another inexpensive reader somewhere with a range of two to three feet?

Thanks,
PeterM

Paul Baker

With passive RFID systems, the RF field generated by the reader is used to power the RFID tag. To extend the range, orders of magnitude increase in the RF field is required and the drop off of intensity of the field follows roughly the inverse cubed relationship. So to achieve a 3 foot range would mean the RF field would have to be roughly 200 times the field strength. Additionally the communication occurs by the tag modulating the RF field, since it's antenna is fixed size, it's ability to modulate is fixed. This means that the signal to field ratio is much lower and the reader's receiver must have a very good SNR in order to pick up the modulation. What this means is that it is possible to design such a reader, however because of it's exponential difficulty of design, the cost will be exponential as well. I know of one type where a doorway jam is the reader and picks up any RFID tag which passes through the doorway, however the reader is many 10s of thousands of dollars.

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Paul Baker
Propeller Applications Engineer

Parallax, Inc.

Phil Pilgrim (PhiPi)

I've seen evidence of the very caveats that Paul mentions. We have an annual footrace which uses RFID chips affixed to the runners' shoes. These are the same low-frequency glass-encapsulated chips that can be read by the Parallax RFID reader. The transceivers are comprised of huge coil antennae embedded in rubber mats that span the finish line, along with massive enclosures that contain the electronics. Yet, even with these, if someone were to wear the chip on their waist instead of on their shoe, they would not be detected.

-Phil