>History of RFID
>Radio frequency identification or RFID, is rapidly becoming wide
>spread enabling remote objects to be identified automatically.
>RFID has been reported upon in Scientific American, the San Jose
>Mercury, and now has its own journal, RFID. The person contributing
>more than any other single individual to this application of radio
>technology is Charles Walton of Los Gatos. The first successful
>application was for an RF coupled proximity key entry through locked
>doors. Mr. Walton formed a company with several associates, and sold
>the technology to Schlage Lock of San Francisco. Millions of radio
>frequency cards using this system have been sold and put into use.
>Mr. Walton invented several distinctly different forms of radio
>frequency ID, licensing the technology to several companies,
>and chose the frequency of 13.56 MHz for the RFID application,
>which has become a standard frequency. Charles also built systems
>to identify vehicles, eliminating the need to stop to pay a toll.
>Walton will talk about his experience with RFID technology, and
>his experiences with starting companies.
>If time permits, Charles will also talk about socially creative
>inventions he has made. He believes that engineers and scientists
>who can create new technical systems are also well equipped
>mentally to solve social problems creatively. One of Mr. Walton's
>social innovations is the sponsorship of an annual essay writing
>contest on social problems.
Charles began his involvement in RFID back in 1970. The RFID system
they developed consisted of a transmitter that sends a signal of a few
milliwatts that sweeps over a relatively wide frequency range, and a
passive receiver that responds at one particular frequency. The
mechanism works on the same principal as a transformer, with the
primary signal being echoed in the secondary. The difference is that at
the much higher frequencies used much less metal is required. The reply
from the passive card is only micro-watts, but that is enough for the
To make the system secure enough for privacy protection systems in the
consumer marketplace, they made the cards with two or more antennas in
them. This made the system immune to false positives, which happen when
the single reply frequency was emitted from some random signal source.
Since then they have made reply cards with as many as five antennas in
Charles passed around a page with the guts of two reply circuits taped
to it. One of them was a consumer tag with a built in solid state
circuit that could reply with a limited pulse pattern and one antenna.
The other was a card for a reader that had four antennas in it. He
demonstrated the card system with a Schlage locking door that worked
when he brandished the right card near the reader and didn't work when
he waved other cards near it. He mentioned how fun it was to get mail
from all over the country after he demonstrated that very machine on
Charles than explained that for most of his patents, they would
generate royalty checks for five years or so after he made a deal with
some company that wanted the technology. Usually after that somebody
else would come out with a better way to do it. RFID was unusual, in
that it kept generating more money per year until the patent expired,
seventeen years after it was granted. Now the keyless entry locks based
on his work are common, but he no longer gets anything out of them.
More recently, the technology has been used to tag goods in stores like
WalMart for theft protection. Airlines are also looking into using them
to tag luggage. Charles expects the number of uses of the technology to
During Q&A a lot of details were brought to light:
The consumer tag with one antenna probably cost the place that used it
(The Tech Museum) about fifteen cents.
The range for a passive receiver/reply circuit is about four or five
feet. For more range it is necessary to put an active circuit with a
power source at the reply card end of the interaction.
The first market were a lot of RFID cards were used was for executive
offices. Apparently they like being able to open doors without turning
keys. Another large early user was casinos.