“…A simultaneous-frequency harmonic radar has been demonstrated in [34,35] for distinguishing two electronic targets. Furthermore, linear frequency-modulated chirp signals [11,12,33,34,36] and stepped-frequency pulses [11,12,33,34,[37][38][39] have been transmitted to targets, enabling both their detection and determination of the range to the targets. Moreover, in [40], a carrier modulation technique was exploited to detect electronic devices remotely using harmonic radar.…”