An active detection approach for hidden radio-frequency receivers discovery

This work explores the possibility of identifying the hidden presence of a radio frequency illegal receiver using an active detection approach. Such wireless receivers are quite difficult to detect because they only receiving wireless signals and never transmit them. In this letter, we show that even a passive receiver might be able to detect by comparing its radar echoes when it is in power on and off states. Using an FM radio as a demonstration, the radar back-scattering characteristics of the telescopic antenna loaded with LC circuits in the FM band is simulated in the full-wave solver. In addition, time-domain radar echoes for different waveforms are studied to investigate the performance of hidden receiver detection.