September 27, 2005
Tag frequencies
RFID tags usually work at frequencies that do not require a licensing fee. The power levels and regulations regarding these tags vary with the country. A 2.45 GHz interrogator in the US operates at a power level that is a hundred times more than what is legally permissible in Europe. This affects the read range of the reader. Passive RFID chips have a frequency breakup as follows:
• Low Frequency - 125-134 KHz
• High Frequency - 13.56 MHz
• UHF - 868 to 928 MHz
• Microwave - 2.45 GHz
A lot of low-cost RFID tags use a frequency of 13.56 MHz, which allows a balance between tag size, cost, and the two extreme alternatives, i.e., LF and UHF. Tags operating with a frequency of 13.56 MHz can have their antennae coils printed as the number of coils required is less. Tags working with this frequency are common in Japan and are preferred for smart cards as well as airline baggage tags. UHF tags are used mainly for tracking vehicles and freight.
In Japan, tags used for freight tracking can only operate with a frequency of 2.45 GHz; this gives them a range of several meters. A 900 MHz UHF tag used for tracking purposes in the US has a read range of 10 meters. Microwaves can give the smallest tag size and an intermediate range. The frequency selected affects the size of the antenna and the outer protection as well.
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