Near Field UHF Versus HF
May 16, 2006
Item level tagging is going to be the biggest market for RFID. It has special requirements - for example, the tags must be very small and be read in large groups, with no confusion about which is which. Water and metal are frequently in, on or near these items, yet exceptionally high read accuracy is demanded with drugs, jewellery etc. Smart shelves, often made of metal, need to distinguish one from another, however small the items are and there must be robust capability for multi-tag reading.
Wal-Mart mandates UHF for item level drugs: many leading drug companies, all libraries and most laundries fit HF RFID on their items. There is not room for two tags on many of the items. We must not repeat the lunacy of anti-theft tagging where consumer goods suppliers alternately have to fit one of three incompatible tags on each type of item depending on who buys it and there are three incompatible infrastructures out there. Even two incompatible systems for the same items would be problematical and expensive.
To make matters worse, the transition from case to item level is far from distinct. 15% of Wal-Mart's general merchandise is "case pack one-of-one". It is therefore difficult to separate "item" vs "case", if there is to be one type of tag for each.
Best of both worlds?
Recently, many of the UHF proponents have switched to recommending what they see as a "best of both worlds" hybrid called Near Field UHF, although it has limited commercial availability as yet. Technically, this usually means that the standard UHF Gen 2 chip is used in the tag but a different antenna is fitted to tag and interrogator so they work at H Field in so-called near field coupling i.e. like an HF tag.
With a very simple antenna printable at high speed, this will be the cheapest EPC tag. To a large extent, it gives the best of both worlds and it can be combined with conventional long distance E Field UHF by having dual antennas in tag and interrogator - or different interrogators can be used for the two types of UHF label - pallets/ cases vs items, say. Or such is the dream.
If near field UHF lives up to its promise and its limitations are overcome such as high interrogator cost, then its potential cost and other benefits may lead it to being used on a lot of items. However, we shall not have one-tag-fits-all because combined NF/FF UHF tags are too big for many items and UHF tags for pallets, cases, air baggage etc will always need to come in many variations tuned to what they are to sit on. That is a problem with UHF.
Not surprisingly then, no supplier is ceasing its activity in HF RFID and some UHF RFID suppliers are broadening their capability to HF. Hedging of bets may be in order and the likely outcome is that there will be a place for both solutions but rarely on the same product.
Complex matter – winners and losers
The impending stand off between these options in RFID in general is a complex matter and IDTechEx technical experts have taken inputs from many of the most respected designers to create a mini paper Near Field UHF vs HF for Item Level RFID - an Independent Analysis. This has 5000 words, eight figures and a detailed comparison chart and it can be purchased for just $189 / €149 from here. Getting it right is key to the commercial success of the many RFID companies now in this enormous but fast changing market arena.
Dr Richard Fletcher of TagSense will demonstrate NF UHF and Ian Forster, Technical Director RFID of Avery Dennison also clarify the position at the forthcoming IDTechEx conference RFID Smart Labels Europe London September 19-20 www.smartlabelsEurope.com
For further information, also see Item Level RFID.