Range Resolution Enhancement for Miniature Dechirped MMW MIMO-SAR

With the development of miniaturized millimeter-wave (MMW) frequency-modulated continuous-wave (FMCW) radar, the dechirp-on-receive technique has been widely used. Due to the limitations of highly integrated radar hardware, it is difficult to further increase the bandwidth of the transmitted signal. Therefore, enhanced range resolution in MMW synthetic aperture radar (SAR) imaging can be achieved only, thanks to suitable postprocessing. In this article, we propose a method for range resolution enhancement based on the principle of wavenumber shift with application to cross-track miniature MMW multiple-input and multiple-output (MIMO)-SAR systems. An improved orthogonal waveform design scheme of multi-subband chirp waveforms with chirp rate changes between waveforms is proposed, which is suitable for dechirp processing. In addition, given the constraint of the position of the equivalent SAR platform of MIMO-SAR, which leads to the lack of range-dimensional spectrum, a spectral data interpolation method based on autoregressive (AR) modeling in the time-frequency (TF) domain is proposed. The effectiveness of the proposed method is verified by numerical simulation and experimental data processing.