Fast-Time Clutter Suppression in mm-Wave Low-IF FMCW Radar for Fast-Moving Objects

A dual-DDS-based, mm-wave, heterodyne, FMCW radar with a 108-GHz center frequency, a 600-MHz bandwidth, and a 3-MHz IF was used to characterize backscatter from static clutter and a small, fast-moving target. Employing a symmetric triangular frequency-vs-time FMCW waveform with 500-us up-chirp and down-chirp durations, signals from a reusable paintball (reball) with a radial velocity of about 90 m/s were measured in an indoor, clutter-rich environment over intervals of ∼100-ms. Unambiguous estimation of the reball's range and radial velocity were derived from observations made during both the up-chirp and down-chirp observations. Specifically, when the reball's echo signal was obscured or degraded by coincident clutter (e.g. during down-chirp), estimates of its amplitude characteristics were obtained from measurements when the reball and clutter were spectrally separable (during up-chirp). Consequently, it is demonstrated that the clutter in this context can be suppressed by more than 25 dB.