MIMO SAR Waveform Separation Based on Costas-LFM Signal and Co-arrays for Maritime Surveillance

In case of bright targets over a dark background, the cross-correlation noise of Multiple input and multiple output (MIMO) Synthetic aperture radar (SAR) orthogonal waveforms in the same frequency coverage will increase which can degrade the image. An Inter-pulse Costas hopping and intra-pulse Slope coded linearly frequency modulated (IPC-SCLFM) waveform is designed and analyzed to decrease the autocorrelation and cross-correlation noise. Besides a novel acquisition mode of "MIMO Coprime SAR" (MIMO-Cop SAR) is proposed with Coprime arrays (Co-arrays) in receive across the SAR line of flight based on digital beamforming. An improved processing by multiplying values at each pixel of two co-arrays images is proposed to suppress the cross-correlation noise. MIMO-Cop SAR can effectively suppress the cross-correlation noise, reduce the amount of data to be stored and get high signal-to-noise ratio in a simple way. The effectiveness of MIMO-Cop SAR for maritime surveillance is demonstrated by the simulation experiments.