UHF RFID is of interest in the printing of electronics because the antennas are often printed with silver ink today, either by gravure, flexo or screen printing and the logic will be printed one day - all to save cost. It is one of the fastest growing types of RFID because it can sometimes give longer range, better multi-tag reading and so on but it is a long way from being the most popular RFID frequency by money spent and it is the only frequency at which the tag makers typically lose money. This is because they are pricing for high volumes which have yet to come.
At the IDTechEx conferences Printed Electronics in Asia 11-12 September and RFID Europe in Cambridge UK 18-19 September it was clear that attitudes to UHF RFID are changing. The East Asians were intrigued by the rush to UHF in the West and were keen to follow when their radio regulations permitted these frequencies at realistic power levels. That has now happened and UHF RFID is successfully used on such things as mail bags in China and airport baggage. There has been a honeymoon period when UHF was being tested for a very wide variety of applications in the East and was spoken of a solution for most challenges.
That period is now over, because some disappointments have restricted the vision to a narrower range of applications. The Japanese Government has been concerned that this frequency can interfere with heart pacemakers, so it now requires sites to display notices asking people with pacemakers to keep at least one meter from such tags. That has made one major store chain cancel a UHF trial. Another setback has been radio regulations sometimes permitting only narrow bandwidth, because this can cause a problem with readers interfering with each other and designers being unable to escape interference from other devices.
Major advance by Impinj
Impinj acknowledged the considerable problems with water and metal with conventional (ie "Far Field") UHF in its presentation but it has now fully proved an alternative, notably for item level tagging, where so called Near Field UHF is used with inductive coupling mimicking the way an HF tag works. Range is modest at no more than 50 centimeters but that is no problem for most item level tagging. The antenna has a simple single turn of printed metal, this being cheaper than the HF alternative which would typically need seven turns and a crossover.
The use of UHF is uncertain for the future. It will gradually be used on more and more airline baggage under the IATA standard with problems of water and metal reduced by faraday cages and tunnel readers. Following great success in the dry and relatively non-metallic environments of Selexys bookshops in the Netherlands and Marks and Spencer apparel stores in the UK, it may or may not succeed in the wet, metallic environment of pallets, cases and items in food retailing. Metro Germany and Wal-Mart USA certainly think they have cracked the problems at pallet and case level and they are fixed on UHF but many suppliers point to poor read rates.
Two views in healthcare
Hospitals are jumpy about potential interference with life support equipment and some healthcare professionals fear heating and thus damaging drugs when the tag is on the bottle. However, Purdue Pharma has scaled up its UHF tagging of drugs for anti-counterfeiting purposes.
Cost comparisons questionable
IDTechEx does not believe that a lower cost for Near Field UHF vs HF for item level tagging systems has yet been proven. The saving in the printed antenna may be offset by the fact that UHF may never be one bandwidth, frequency, signalling protocol or power level under radio regulations across the world and workrounds cost money, whereas HF is a simpler, well proven prospect. Near Field readers need a different antenna from Far Field but the electronics can be the same.
The global standard for RFID enabled mobile phones is at HF, as with library books, cards, tickets, passports and so on. However, East Asian mobile phone companies have been trialling UHF for RFID enabled phones currently used at HF by 40 million Japanese to access transport and to buy things. The reason is that, as phones get smaller, it is increasingly difficult to get enough range with HF. One Western phone maker is starting to think along similar lines. Presumably they do not expect people to be required to keep one meter away from their phones! Will that be Near Field (range restricted) or Far Field (problems with water, metal, curved glass focussing the beam, fears for human health)? The situation remains fluid.
If you were unable to attend these events you can purchase the audio and presentations for Printed Electronics Asia from firstname.lastname@example.org or online for RFID Europe.