NEC-LIST:Modulated RFID tags, etc.

Christ Turner broached the subject of RFID tags and their workings in a
recent e-mail.

First, a little background. I hired Jerry Landt, mentioned in Turner's
message, into my group at LLNL upon his graduation from Stanford about 1973.
His initial assignment was on an EMP program we had, in particular to become
acquainted with, and to extend, the TWTD (Thin-Wire Time Domain) code for
EMP applications. Eventually, we became interested in hybridizing TWTD with
a circuits code to handle the effects of non-linear protection devices that
might be used to mitigate the potential damage caused by EMP.

Sometime later, Jerry left LLNL for LANL. At some point he became involved
in a project to develop a passive tag for use in electronic cattle
"branding," work that was sponsored by the US Dept. of Agriculture.
Although fairly successful, interest in the electronic tag waned and the
patents were made available to a startup company called AmTech (for Animal
Technology). At some point I believe, H. Ross Perot became an investor.
The electronic tagging business has really taken off, no double in some or
large part to Landt's work at AmTech.

Much later, I joined LANL as a Group Leader in the same department that
Landt had worked. I mentioned some other possibilities to a few people in
my group for affecting the scattering properties of an object using a
modulated impedance, and upon returning from a trip found a hallway
demonstration set up using this idea. The difference between our
implementation and AmTech's was use of a small battery in our device so that
not all power had to be supplied by an illuminating signal. We eventually
were funded to develop a passive (one active node, with the remaining ones
passive) two-way communication (or more) system based on this idea. Adding
the battery increased the range from a few meters to a few kms. This work
is described in only one open article that I'm aware of, "R. Bracht, E. K.
Miller and T. Kuckertz, An Impedance-Modulated-Reflector System, IEEE
Potentials, Vol. 18, No. 4, October/November 1999, pp. 29-33," that might
answer some of the questions Chris raised. Our system used an X-band
doppler radar for the active node, and was designed to access video from a
remote monitor.

Ed Miller

----
Dr. Edmund K. Miller
3225 Calle Celestial
Santa Fe, NM 87506-1213
505-820-7371 (Voice & FAX)
ekmiller_at_prodigy.net
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