An Introduction to RFID?

RFID or Radio Frequency IDentification is a technology based on the transmission and reception of radio frequency (RF) signals between a transmitter or Reader and a transponder or Tag. In most cases the transmission is two-way, the transmitter sends signals, which the transponder receives, the transponder then transmits a response signal that is received by the transmitter. The information from the transmitter can then be used to identify the transponder and any item it is attached too.

RFID Readers, and Tags work in many frequencies and are available in either Active or Passive formats.

Active transponders are battery powered, see our section on active tags. This gives them much longer response distances and as such the transponders can be read over a greater range in some circumstances several 10’s of meters. However active transponders are typically expensive and as such are generally used on items such as vehicles, shipping containers and assets where access is restricted. Being battery-powered they have a limited lifetime.

Passive transponders take the power they to need to respond from the electromagnetic signals transmitted by the reader. The electromagnetic signals have two components, a magnetic or inductive field (known as the H-Field) and the electric or capacitive field (known as the E-Field).

The most common frequencies for Inductively coupled transponders are 125 -134.2 KHz, known as Low Frequency or LF and 13.56MHz known as High Frequency or HF. The H-Field is well defined and able to penetrate most materials however, the strength of this field falls off quickly giving limited read ranges.

LF is commonly used in applications where a strong response is required and the field needs to be confined. Livestock, vehicle and process control applications suit LF well. See our section on LF transponders for the types available.

HF is more commonly used in applications where the transponder needs to be thin and easily converted in to a label, applications such as item tracking, document tracking and access control suit HF well. See our section on HF transponders for the types available.

Systems operating with the electric field operate in the range of 860 ?960MHz which is known as Ultra High Frequency or UHF . The pattern of the E-Field is less well defined and its strength doesn’t fall off, as quickly. As such, long read ranges are possible. However UHF systems do suffer signal loss or attenuation through materials and as such are not as good at penetration. So, these systems are more likely to be used in case and pallet tracking, tracking large items through the supply chain and in the retail sectors.

See our sections on UHF transponders and readers for more information.



Technical Downloads

Choose from our selection of technical downloads which are available for you to read at your leisure. Also see Wikipedia.

High Temperature RFID

Tagging of Metalic Objects in Harsh Environments