Getting the Bugs Out: A Portable Harmonic Radar System for Electronic Countersurveillance Applications

The concept of a radar that detects semiconductor and metallic objects by monitoring second and third harmonic reradiations was conceived over 35 years ago. Called harmonic or nonlinear [1], [2], these radars can transmit at one or multiple frequencies and then receive the reflected signals at, or close to, the harmonic frequencies. Recently, harmonic radars have been used in different applications such as insect and bee tracking, vital-sign monitoring, antitheft systems [3], vehicular detection and identification, and countersurveillance [4]-[7]. Important design metrics for harmonic radars include operating frequencies, waveforms, polarizations, power levels, false-alarm rates, and detection sensitivity and range [5].