A passive radio frequency excited acoustic transducer

The physical processes that govern the operation of a passive acoustic transducer driven into operation by a broadcast radio-frequency electromagnetic wave are presented. The transducer is comprised of a re-entrant cavity resonator operating in its resonant TEM mode and a sensing membrane. By displacing the membrane using the acoustic pressure, one can generate an amplitude modulated radio frequency signal proportional to the product of the displacement and the excitation signal. One may use the backscattered electromagnetic signal to recover the audio signal. The results for power generation, sound transduction, and radio-frequency backscatter transmission of the audio signal are presented.