What’s the difference
between passive and active tags?
Active RFID tags have a battery, which is used
to run the microchip's circuitry and to broadcast
a signal to a reader (the way a cell phone transmits
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 a dollar or more, making them too
expensive to put on low-cost items. The Auto-ID
Center is focusing on passive tags, which cost
under a dollar today. Their read range isn't as
far - less than ten feet vs. 100 feet or more
for active tags - but they are far less expensive
than active tags and require no maintenance.