Dual-frequency Doppler radars for indoor range estimation: Cramer-Rao bound analysis

Single frequency Doppler radars are effective in distinguishing moving targets from stationary targets, but suffer from inherent range ambiguity. With a dual-frequency operation, a second carrier frequency is utilised to overcome the range ambiguity problem. In urban sensing applications, the dual-frequency approach offers the benefit of reduced complexity, fast computation time and real-time target tracking. The authors consider a single moving target with three commonly exhibited indoor motion profiles, namely, constant velocity motion, accelerating target motion and micro-Doppler (MD) motion. RF signatures of indoor inanimate objects, such as fans, vibrating machineries and clock pendulums, are characterised by MD motion, whereas animate translation movements produce linear FM Doppler. Cramér-Rao bounds (CRBs) for the parameters defining indoor target motions under dual-frequency implementations are derived. Experimental data are used to estimate MD parameters and to validate the CRBs.