Are such tags active or passive?
The term "chipless RFID" is often used to describe two different types of radio frequency identification transponders.
One type employs integrated circuits (chips) made of conductive plastics or polymers instead of silicon. These transponders function in the same way that conventional tags with chips function, but typically have a shorter read range than conventional tags since the materials they are made from are not as efficient as silicon. The expected benefit of these types of chipless tags is that they will be cheaper than those containing silicon chips. So far, they have not made much of an impact on the market, but researchers continue to work to improve their performance.
Another type of chipless tag takes a very different approach to conventional RFID. Instead of storing a serial number on a chip, they use other means to identify unique items. Inkode, located in Vienna, Virginia, embeds aluminum fibers randomly in labels or paper. When RF energy hits the fibers, they reflect back a unique signal that a computer can then turn into a serial number (see 1-Cent RFID Tags for Supermarkets).
Additionally, a company called Somark Innovations has developed chipless RFID technology for use in cattle identification. The company's permanent animal ID system works by tattooing an animal with dielectric ink. Data is encoded in the tattoo, and can be read remotely using a Somark reader (see RFID Tattoos to Make a Mark on Cattle Tagging).
I am unaware of any active chipless RFID systems.
—Mark Roberti, Founder and Editor, RFID Journal
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