AM Interrogation of Harmonic Transponders for Measuring Channel Loss

In this work, we demonstrate that the loss of an unknown channel can be found through remote, wireless interrogation of an embedded harmonic transponder. The approach exploits the transponder's nonlinearity, by using a tone modulated AM interrogation signal and measuring the change in the backscattered signal's carrier to sideband ratio. Our results demonstrate that the forward channel loss can be readily determined within ±1.5 dB, regardless of the propagation characteristics of the reverse channel.