Reconfigurable Range-Doppler Processing and Range Resolution Improvement for FMCW Radar

A reconfigurable range-Doppler processing method for FMCW radar is presented. By concatenating beat-frequency signals from more than one sweep, a continuous beat-frequency signal for the whole coherent processing interval (CPI) can be created. As a result, continuous targets' observation time is extended beyond that of a single chirp duration, leading to range resolution improvement. The created continuous beat-frequency signal can be split in the digital domain to any two-dimensional slow-time and fast-time matrices with the same number of elements as in the original signals, which offers a realization of a software-defined pulse/sweep repetition rate in range-Doppler processing. The signal concatenation is done in the short-time Fourier transform (STFT) domain, where the beat-frequency slices are extrapolated to compensate for the observation time lost in the transient region between sweeps, and then a phase correction is applied to each frequency-slice as appropriate, followed by an inverse STFT (ISTFT). The proposed technique is verified with simulation and experiments with an FMCW radar for stable and moving target scenarios. We found that the method allows for range resolution improvement without the transmission of additional bandwidth and also allows for the ability to observe different resolution granularities in parallel from one CPI. It additionally allows the decoupling of the transmitted PRF from the Doppler processing PRF, permitting the facility to observe different unambiguous Doppler velocity intervals from one CPI, without compromising on the total CPI processing gain.