What does RFID mean?
RFID stands for Radio Frequency Identification. In other words it is a technology that allows us to Identify people or object by the use of radio waves. There are different techniques to realise the automatic identification. Well known to-day is the barcode scanning, magnetic stripes reading on plastic cards or biometric techniques to identify people. Special about RFID is the fact that it works on a distance even without direct mechanical or visible contact between reader and object. That makes it possible to open up doors just by keeping a wallet with a tag inside near to a reader.
Sinking prices for transponder chips and technological progess have made RFID meanwhile very affordable, secure and easy to implement. A range of ISO-norms meanwhile guarantee the compatability of different tags and readers. This standardization further raises the attractivity of RFID for an endless range of applications.
Generally we speak about 3 different RFID technologies consisting of passive, semi passive and active systems.
Using this method, the transponder is connected to an antenna and packed inside a badge or tag. When presented to a reader, the inductive energy from the reader brings a little current to flow inside the antenna. This energy allows the transponder chip to send out its ID-number, which in return is registered by the reader. This way it is possible as well to store and change information inside the transponder. Due to the inductive energy, there is no need for batteries inside the tags. The most commonly used frequencies are 125 KHz and 13.56 Mhz. The reading distance in most cases is less than 10 cm which is generally known as proximity coupling. The reading distance can be improved by the use of larger transponder and reader antennas, as well as optimal frequency tuning of both reader and tags.
The terminology semi-passive, stands for RFID tags using a battery that serves the transponder with current. These tags are often called as well “semi-active”. These tags work on the Ultra High Frequency band at 2.45 GHz. Due to the fact that the current from the battery is not needed to actively transmit radio signals, the live time of the battery is generally more than 5 years. The possible reading range is up to 15 meters. Semi passive tags are relatively insensitive to disturbing influences such as signal absorbing- or reflecting materials.
Active RFID stands for transponders that actively broadcast data to the reader allowing reading distances of 100 meters and more. The tags usually work on 865 MHz or 2.45 GHz frequency and receive the necessary energy for the transmission from a build in battery. The electronics and battery make these tags more costly than passive and semi passive tags.
Active RFID Tags not only allow superior reading distances, but are also able to monitor environmental conditions like temperature, humidity or movement using build in sensors.
This way, active RFID tags are very suitable for remote tracking and monitoring of people and goods.
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