Is it the sort of tech used by some devices in the NSA ANT catalog? It is useful for spying because they are undetectable if they are not subjected to a carrier

Is it the sort of tech used by some devices in the NSA ANT catalog? It is useful for spying because they are undetectable if they are not subjected to a carrier frequency. There was also The Thing[1] [1]https://en.wikipedia.org/wiki/The_Thing_(listening_device) https://en.wikipedia.org/wiki/The_Thing_(listening_device)