Best read range for small UHF RFID tag
Category:UncategorizedBest read range for small UHF RFID tag.
I recently had a client discuss a need to track many things that are small and thin – very important documents. The actual business case was to receive hundreds of documents each day, disassemble, sort, reassemble and group these documents and then mail out batches. Not one document could be lost, stolen or mis-routed.
I’m sure that there are lots of ways to skin that cat, but in this case, we were looking to see if far-field UHF passive RFID (pRFID) would work for this client. Passive RFID has come a long way in the past year and the hype of the Internet of Things has been great to put this technology into the front of the public conscience. pRFID is an extremely flexible technology with many variations that work in many different situations.
For this client, we were seeking a medium-range (far-field) UHF RFID solution. We wanted a solution that used small tags and an infrastructure that could read hundreds of tags, several feet, quickly. This way, we could minimize our impact to their existing business process. I found it was surprisingly hard to find read range information on tags that had small footprint. We procured and tested likely tags and decided to publish our findings on the selected tag. The best inlay-type tag in the smallest form factor we tested was the Alien Square 9629 tag.
Alien Square 9629
The Alien Square 9629 is a 1″ x 1″ tag – purported by Alien to provide performance of a 2 x 2 tag. It is EPC Gen2, Higgs 3. It was difficult to obtain less than a roll for testing purposes, (for me at least) and we ended up going directly to an offshore manufacturer to get 30 tags to test. We then waited a couple weeks for these tags to arrive. We tested these tags on our system(s), and also asked a partner company to test on separate platform(s) to validate our findings. Here are the results.
Impinj Speedway Revolution R420 reader and +9 db circular antenna. At full power, we were able to read some tags (not all in sample) at 13ft (4m). At 10′ (3m) we were able to see all tags, but noted significantly different RSSI values for different tags at the same range.
AWID 2010BN reader and +6 db circular antenna. Max read range up to 2.5m.
(Proprietary) VFR18 fixed reader and +9 db circular antenna. Max read range up to 3m.
AWID HB2000 (Handheld) reader. Max read range up to 0.7m.
Our results and conclusion were somewhat disappointing. The tag read ranges were acceptable at 3m and the tag footprint was acceptable at 1″ x 1″ for this business case. However I was not happy with the variation in reads from the tags. When testing several tags at the same range in a controlled test, we were getting variations in power (backscatter) of up to 4 RSSI. This means that, at range, some of the tags were not able to return enough power to be read. Perhaps this was due to the tag source (manufacturer) quality, but still disconcerting none the less.
If this is the best tag available, we can make it work with appropriate tuning and testing – perhaps modify the process workflow somewhat, but I would love to hear if anyone has had other experiences with these other small (inlay/label) UHF tags. Regardless, hopefully someone looking for a small far-field tag can use this information to save themselves some time and effort. Happy Tracking! Lewis Kilby, eChain Technology
