Active RFID tags have a transmitter and their own power source (typically a battery). The power source is used to run the microchip's circuitry and to broadcast a signal to a reader (the way a cell phonetransmits signals to a base station). Passive tags have no battery. Instead, they draw power from the reader, which sends out electromagnetic waves that induce a current in the tag's antenna. Semi-passive tags use a battery to run the chip's circuitry, but communicate by drawing power from the reader. Active and semi-passive tags are useful for tracking high-value goods that need to be scanned over long ranges, such as railway cars on a track, but they cost more than passive tags, which means they can't be used on low-cost items
Generally speaking, active tags have a much longer read range—300 feet ( 100 meter) or more—than passive tags. The read range of passive tags depends on many factors: the frequency of operation, the power of the reader, interference from other RF devices and so on. In general, low-frequency and high-frequency tags tags are read from within three feet (1 meter) and UHF tags are read from 10 to 20 feet ( 3~ 6 meter), Readers with phased array antennas can increase the read range of passive tags to 60 feet or more ( 20 meter or above).
For details ,check the following chart.
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