I received an e-mail the other day from Steve Depp of Katonah, N.Y., correcting some information in our History of RFID Technology feature. The article, which has been corrected, indicated that the Los Alamos National Laboratory, at the request of the U.S. Department of Agriculture, developed a passive low-frequency transponder to track cattle.
Depp wrote: “I was the initial leader of the Los Alamos team, and our agricultural system was actually a radiative backscatter UHF system running at 915 MHz (not 125 kHz). This gave us much larger range and directionality than the low-frequency, induction-based transponders used for applications like building access.”
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He cited U.S. Patent 4,075,632 and several articles for my reference, and even attached a wonderful photo (at left), taken in December 1973, of Los Alamos’s first RFID system running at 915 MHz. The photo shows both active and passive transponders (in the lower right quadrant of the picture). Each returned 12 bits of digital data that made up the ID and an analog channel (the subband), which was used to transmit temperature.
I asked Depp why they had chosen UHF. (I had been told it was an LF system, and that it had been chosen because LF works better around the water in the animal’s flesh.)
Depp’s response: “The reason we developed UHF tags was to get a larger range—at least several meters—for some of the animal applications proposed at the time. For example, one idea was to monitor not only the ID but also the temperature of cattle in a feedlot each time they came near a trough to get a drink of water or some feed. It was hoped that an activity and temperature history for each animal would allow an early health intervention, when needed, or even a diagnosis (e.g., brucellosis, or undulant fever, has a characteristic temperature signature).”
According to Depp, Los Alamos was also interested in UHF for non-farm applications. “For example,” he wrote, “RFID tags were envisioned for quick, automated inventory control in rooms where many containers of radioactive, fissionable material were stored. You obviously want to be sure all the containers are properly inventoried, but you also would want to do this quickly, and at some distance away. By the way, our ability to simultaneously measure an analog variable like temperature could have been a real advantage in this potential application since each container actually self-heats, and temperature is indicative of the amount of material inside.”
I thank Mr. Depp for correcting the article on our site. We are always interested in providing the most accurate information to our readers. I’m also grateful that he took some time to shed some light on this early chapter in RFID’s history.