Tracking the dynamic motion of held objects using pulsed harmonic Doppler radar

Tracking the motion of held objects is becoming increasingly important in smart home applications. MicroDoppler radar has proven beneficial for tracking the motion of people, as various parts of the body, such as the arms and legs, move with different velocities as a function of time, thereby generating different Doppler frequency sidebands in the received response. The time-frequency signature of these responses can be used to classify activities. Since natural objects are generally linear, the back-scattered signals are collected at the same frequency as the transmitted signals, thus the micro-Doppler frequency sidebands are observed around the transmitted center frequency. In home settings, clutter can thus become a challenge in the detection of small movements. In this work, we demonstrate an approach for tracking held objects in high-clutter environments using harmonic Doppler and harmonic tags to detect the micro-motion signatures of held objects. While previous works have investigated harmonic radar for target tracking, this work uniquely focuses on detection of the timevarying Doppler responses from micro-motion signatures of held objects. By placing a passive harmonic tag on various parts of the human body, the motion of individual body parts and/or individual held objects can be discerned. In this work we characterize the harmonic micro-Doppler signatures of tags held on different parts of the body. We present expected results and compare them to measurements conducted using a 2.51 GHz/5.02 GHz harmonic Doppler radar