How RFID works

Action through RFID

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The main purpose of RFID is to track things. We are using a generic term here, because the range of items that can be tracked is huge. You have probably seen scientific programs which show you a world of the future where you pass all your groceries through the checkout in a single process. You dont have to wait, you just walk on by, knowing that all the items in your basket have been scanned and added up without any scanning or checkout delays.

What you probably don't know is that, when you buy a day ticket on a metro, then the same basic technology is being used to track where you started and where you ended your journey. The meat in your grocery basket has been tracked throughout its lifetime using something like an ear tag which records all the movements of the animal without any direct scanning being required. Your Wallmart groceries were marshalled through the supply chain and noone had to worry which way up the pallets were, and the logistics chain did not have to stop for codes to be counted and measured.

RFID uses wireless technology - very similar to the wireless technology you use to ensure that you can connect to the internet anywhere in your home or office. The frequencies may be different, but the idea of a network of products, all being scanned simultaneously in a real-time or live environment is exactly the same.

Let's then consider the nature of RFID in more detail.

What is it?

The easiest way to explain RFID is by comparison with barcodes.

The barcode is a machine readable technology. Alternating black lines and white spaces create a fingerprint or code that can be scanned and used to look up the identity of a product or parcel. The easiest example to give is when you come to the checkout at your local supermarket, the cashier will present the code to a scanner; the number is looked up; the product identified; and the appropriate item added to your bill. We are all very familiar with this type of technology.

The key things are to note are that the items have to be scanned one by one and that the code has to be presented correctly to the scanner.

Depending on the technology of the RFID device used (we will cover the differences elsewhere), RFID does not have these restrictions. Data can now be stored on the device itself, and there is no longer any need for line-of-sight to ensure a read. As long as the RFID devices are in range, then many can be read all at once.

Different tag types

Tags fall into two different forms of signal transmission:

Inductive coupling - which is the form used by Low Frequency (LF) tags

Backscatter - the most commonly used in the microwave and UHF ranges of tags