For example, is there an RFID or beam-steerable phased-array antenna that could be used to track a passive tag from a satellite via a smart phone? You may have read about voluntary RFID implants in countries such as Sweden, but I assume those implants wouldn’t be strong enough to emit a signal that would be traceable from a satellite or smartphone 80 feet away. I had an RFID implant, but I forget which part of my body it was implanted in. Do you know of any handheld device which I could wave over my body to detect the presence of an RFID implant, and where such a scanner could be purchased? Any assistance would be greatly appreciated.
—Otto
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Otto,
There are beam-steerable phased-array antennas that can read a standard passive UHF RFID tag from about 600 feet. If you used a tag with an extra-large antenna, you could maybe get to 1,000 feet. There is no way to read a tag from a satellite. It is simply impossible.
Passive RFID transponders do not emit energy—they use the energy from the reader to respond. Passive UHF transponders employ backscatter to respond. They take energy from a tag and modulate and demodulate their own antenna to reflect a signal back to the reader antenna. Think of the reader antenna as a powerful light on a boat on the ocean at night. The light flicks on and off to send information to a much smaller boat. That smaller boat then uses a mirror to reflect a signal back to the first boat. Passive LF transponders, the kind used in subcutaneous RFID systems, employ a different communication method called inductive coupling. The loop antenna in the transponder forms an electromagnetic field with the looped antenna of the reader. The reader emits energy to create this field.
It is like a balloon that you and I both hold together in our hands. I squeeze the balloon in Morse code, and you can feel the changes in the balloon and thus read the code. The size of this balloon is determined by the size of the loops in the reader and tag antennas, as well as the amount of energy. Generally speaking, you would not be able to read a tag from more than a few inches away, though if you had a really big loop in the reader antenna, you could get it up to a few feet.
I do not believe that anyone has ever been injected with an RFID transponder against their will, simply because the tag would only be readable from a few inches away. What would be the point? It would be like spying on someone with reading glasses. If you are convinced that you have a subcutaneous RFID transponder in your body somewhere, you could try purchasing an LF reader, but if the tag used a different protocol, you would probably not be able to read it. A full-body x-ray would reveal the tag’s location, since the tag would have a metal antenna that would show up on film. I hope this information is helpful.
Mark Roberti
Founder and Editor
RFID Journal
Rich Handley Staff asked 4 weeks ago 
