Range-time-frequency representation of a pulse Doppler radar imaging system for indoor localization and classification

Pulse Doppler radars using UWB technology are becoming very popular for their wide range of capabilities and applications. UWB waveforms are used for imaging in indoor environments, target localization and classification behind walls, and evaluating micro-Doppler signatures. Typically, CW and FMCW radars are used for measuring time Doppler frequency shifts and subsequently providing time-frequency signals. Meanwhile, UWB pulse Doppler radars provide range-time-frequency representation. This representation provides both highly accurate range and micro-Doppler information. This 3D representation (i.e. time, frequency, range) can be effectively used for detailed human gait analysis, tracking more than one object at a time even behind walls as UWB radars allow clutter removal and wall mitigation. This paper is an overview of such activities.

I. Introduction

Mechanical vibrations or rotations of structures on a target may introduce frequency modulation on the radar return signal. The modulation due to this vibration or rotation is referred as micro-Doppler (m-D) phenomenon. For example, human physical activity is a complex motion that is comprised of movements of individual body parts, including head, torso, leg, arm and foot. Whenever a human is walking, the movements of different components of its body generate a number of different frequency shifts in the radar returned signal, also called Doppler frequency shifts.