Measurement of the Radial and Angular Velocity of Tagged Objects Using Interferometric Harmonic Micro-Doppler Radar

We demonstrate the joint detection of the radial and angular velocities of tagged moving objects using a harmonic radar with dual interferometric-Doppler measurement modes. The radar transmits a continuous-wave signal which is incident on a compact harmonic tag affixed to the moving object. The tag generates and re-transmits a signal at the first harmonic frequency, 11.4 GHz, which is more easily detected at the radar in complex environments than the scattered 5.7 GHz illuminating signal which can be masked by clutter responses. The radar receiver consists of an interferometric antenna pair separated by 10 wavelengths. Each channel provides a Doppler response, from which the radial velocity can be detected, while the complex cross-correlation of the output of the two receivers provides an interferometric frequency response that is proportional to the angular velocity of the object. We demonstrate the concept using at 5.7/11.4 GHz interferometric harmonic radar and show the time-frequency responses of a sinusoidally-moving harmonic tag.