MIMO FMCW SAR system using beat-frequency division waveforms

Special attention has been devoted to the lightweight, cost effective frequency modulated continuous wave (FMCW) synthetic aperture radar (SAR) in recent years. However, FMCW SAR is not feasible in the case of wider swath or higher Doppler bandwidth, because the loss of range resolution is dramatic and the system sampling rate is high. By using the technique of multi-input multi-output (MIMO), the pulse repetition frequency (PRF) of the system can be reduced dramatically without causing azimuth ambiguities. Consequently, the sweep cycle is increased, the system sampling rate is reduced, the loss of range resolution is negligible and the transmitter-receiver isolation is sufficient. The orthogonal signal transmitted in the system is beat-frequency division waveform. As the bandwidth of the beat signal is much smaller than the signal bandwidth and radio frequency (RF) carrier frequency, the difference between the transmitted signals wavelength is negligible, and the residual phase error caused by compensating phase shift can be ignored. Theoretical analysis and simulation results illustrate the feasibility of this system.