>> RFID Technology News >> Passive rfid tag and Active Rfid tag
What the differences between the passive rfid tag and active rfid tags?
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 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.
| Tags and features |
Passive tag |
Active Tag |
Semi passive tag |
| Internal power Sourse |
No |
Yes |
Yes |
| Signal by backscattering the carrier wave from the reader |
Yes |
No |
Yes |
| Response |
Weaker |
Stronger |
Stronger |
| size |
Small |
Big |
Medium |
| Cost |
Less expensive |
More exprensive |
Less |
| Potential shell life |
Longer |
Shorter |
Longer |
| Range |
from 10cm to few meters |
>100 meters |
>100 meters |
| Sensors |
No |
Yes |
Yes |
Passive RFID requires stronger signals from the reader, and the signal strength returned from the tag is constrained to very low levels. Active RFID allows very low-level signals to be received by the tag (because the reader does not need to power the tag), and the tag can generate high-level signals back to the reader. Additionally, the Active RFID tag is continuously powered, whether in the reader field or not. Active tags can also 'beacon', or initiate communication with a reader (or other tags) when certain conditions are present. Active tags can contain external sensors to monitor temperature, humidity, motion, and other conditions.
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