How can I make a really tiny tag—only 3 to 5 millimeters—and what limits are there for passive RFID?
There is a passive ultrahigh-frequency (UHF) tag currently on the market from Hitachi, known as the µ-chip (mu chip), that measures 0.3 millimeter square (0.01 inch square). The antenna is etched into the chip, which carries a 128-bit serial number (see Hitachi Unveils Smallest RFID Chip).
In addition, Murata Manufacturing Co. offers a high-frequency (HF) tag (model LXMS33HCNG-134) that measures 3.2 millimeters (0.13 inch) in width and length, and 0.7 millimeter (0.03 inch) in thickness It has 1024 bits of memory (see Murata Mass-Produces 'World's Smallest HF Tag').
It is possible to produce a small tag with a greater amount of memory (up to 2 kilobytes). However, a very small tag would have a very short read range, since a small antenna can capture a lot of energy from a reader, but it cannot reflect back a strong signal to a reader antenna.
—Mark Roberti, Founder and Editor, RFID Journal
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