October 01, 2005
A comparison of tag frequencies
In the case of passive RFID tags, the frequencies in the range of 125-135 KHz are considered low frequencies. They are suitable for working around corners and can pass through most objects. They are cheaper to work with and are more tolerant of reflections and radiations. These are used for tagging livestock, beer barrels, etc. 13.56 MHz is considered to be high frequency and has a range of 1 meter. It is reasonably tolerant of liquids and metals and has the advantage of a global standard. Frequencies in the range of 868-930 MHz are referred to as ultra high frequencies; these have a range of around 30 meters. Frequencies in the range of 2.45-5.8 GHz are referred to as microwaves. These have a long range, fast transfer of data, and the tags are small and cheap to produce. The higher frequencies find application in item-level tagging, conveyance, access security, etc.
In general, these frequencies affect the cost, size, and performance of the tags. Low frequency tags use a large-sized antenna to obtain the best transmission range. Their speed of transmission is quite slow. They have the advantage of working well in the presence of obstacles. The reduction in the power of low-frequency tags is equivalent to the cube of the distance traveled. The higher energy with high frequency tags allows them to transmit over a longer range and at higher speeds, the higher frequencies enable a three-dimensional search of smart tags. With high frequencies, power reduces by the square of the distance traveled. High-frequency beams are not very tolerant of obstructions and are affected by irradiation, reflection, metals, etc.
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