What is RFID ?

RFID stands for radio frequency identification. This is a complementary technology to bar codes. RF tags, or "transponders" (from TRANsmit-reSPOND), can be used to carry data about the things to which they are attached. Thus we see RFID technology applied in livestock farming (to trace the history of each animal), car manufacturing (build history of each vehicle) and freight (shipping manifests), to name a few applications.


RF Tags - There are two general types, passive and active. Active tags have a built in power cell and have a higher communication range, but a life limited to the life of the power cell. Passive tags carry no on-board power, but derive it from the reader, giving them a practically unlimited life but a shorter range.

For most general applications passive tags are usually the most cost effective. These are made in a wide variety of sizes and materials: there are durable plastic tags for discouraging retail theft, wafer thin tags for use within "smart" paper labels, tiny tracking tags which are inserted beneath an animal's skin and credit card sized tags for access control. In most cases the amount of data storage on a passive tag is fairly limited - capacity often being measured in bits as opposed to bytes. However for most applications only a relatively small amount of data usually needs to be codified and stored on the tag, so the limited capacity does not normally pose a major limitation. Most tags also carry an unalterable unique electronic serial number which makes RFID tags potentially very useful in applications where item tracking is needed or where security aspects are important. The read/write range depends on the tag's type, active tags generally having a longer range than passive tags. For passive tags the most critical range aspect is the type and size of the reading antenna.

Frequency ranges - There are three frequency ranges in RFID systems. Low frequency (100 to 500kHz) is the least expensive and has a low reading rate at short to medium distances; typical uses include vehicle immobilising, livestock identification and access control. Intermediate frequency (10 to 15MHz) has a medium reading rate at short to medium distances and is ideal for smart cards. High frequency (850 to 950MHz, 2.4 to 5.8GHz) has the fastest reading rate and long range capability, but requires a line of sight between the reader and tag and is the most costly option; a typical application is automated toll collection.

Reading and Writing Tags - RF tag readers range from desk top devices to hand held computers which can be used to write data to the tags as well as to read them. The choice of reader will depend on the type of application. For example, will it be in a fixed position or does it need to be portable?

Consideration needs also to be given to the type of tags. There are many manufacturers of RF tags and there has been little compliance from one manufacturer to another. Efforts are being made to introduce global standards and some form of uniformity is expected to come about in the next few years.

Smart Labels - The term "Smart Labels" basically refers to super thin RFID tags that are embedded into otherwise conventional labels. From an application point of view the real benefit of Smart Labels is the potential to combine human readable printed data with data storage capability and possibly bar code reading capability by printing a conventional bar code on the label as well. Being able to combine these three forms of readability with RFID "writeability" opens up a range of opportunities for low cost tracking and traceability. Some thermal transfer label printers are now becoming available with the additional facility to write data to a Smart Label at the same time that the label is printed.

Putting together systems - RFID is a specialised but rapidly expanding field. Organisations requiring RFID solutions need to work closely with a systems provider which has in-depth knowledge of the technology and is able to create a complete solution which fits the customer's needs.