RFID tag storage and processing
One important area and function of the RFID tag is the area that handles the information storage and processing. RFID tags range vastly in their capabilities as some do not have their own power, relying on the received signals to provide any power and this limits their abilities. Other RFID tags with their own battery power are able to carry out far more sophisticated tasks.
There are several types of RFID tag that may be used:
One-bit EAS RFID tags:EAS (Electronic Article Surveillance) tags are commonly found in shops and stores to prevent theft. EAS tags are often termed “1 bit” tags. The reason for this is simply that they are only designed to communicate one bit of information, i.e. their presence. They are widely used in anti-theft measures in shops and stores. If the RFID tag is present and active, then it means that the item has not been through the checkout. If they have been passed through the checkout the RFID tag is either deactivated or removed.
Because of their use, EAS tags are used in their millions and possibly the most widely used form of RFID tag. They do not have any memory or other chips as these would make them too expensive. Coupling used for these tags is generally inductive or backscatter. The tags simply consist of a resonant circuit, and the reader is able to detect their presence. A further point to note about EAS tags is that the readers have to sweep across a small frequency band, because the manufacturing tolerances of these RFID tags is such that there is a spread in the resonant frequencies of the different tags.
RFID smart labels:Smart labels are simple RFID tags that are embedded in a an adhesive paper label. The advantage of this form of tag is that they can be used by RFID and barcode readers as well as having the option for human readable characters. They can be used in areas where the end product may enter one of a number of scenarios where the form of reader is not known – for example retail outlets a product may be shipped to may have either a barcode reader or an RFID reader, and outlets will have different options. Therefore to cover all eventualities a combined RFID and barcode tag is printed.
SAW RFID tag:SAW – Surface Acoustic Wave tags form a half way house between the very basic 1-bit RFID tags and the more advanced tags that are available. The SAW RFID tags operate in the microwave region using backscatter techniques, and although they do not have a processor, they can be encoded at point of manufacture with a number. This number is limited by the technology but may be up to 32 or 64 bits.
Smart card tags:Smart card tags are different to smart labels. Advanced smart card tags are used for many applications, and in particular where secure communications is required, for example for transactions involving finance. These cards may have complicated processors on board along with sufficient memory. When using these cards there is a balance to be made between functionality and cost – this needs to be taken at the outset of the design and needs to be carefully balanced.
Although RFID tags may appear to be the more straightforward or simple element within an RFID system, this may not be the case as considerable ingenuity and careful design is required to ensure the RFID tags perform correctly while being capable of being manufactured to a very low cost and within constraints of size, weight, form factor and also reliability. While most RFID tags are very cheap to manufacture, this hides the design behind them.