IRCI-Free MIMO-OFDM SAR Using Circularly Shifted Zadoff–Chu Sequences

Cyclic prefix (CP)-based multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) radar has been recently proposed for distributed transmit antennas, where there is no inter-range-cell interference (IRCI). However, it needs to transmit multiple OFDM pulses consecutively to obtain range profiles for a single swath, which may be too long in time for a reasonable swath width. In this letter, we propose a CP-based MIMO-OFDM synthetic aperture radar system, where each transmitter transmits only a single OFDM pulse to obtain range profiles and has the same frequency band; thus, the range resolution is not reduced. It is IRCI free and can collect full spatial diversity if the transmit antennas are distributed. Our main idea is to use circularly shifted Zadoff-Chu sequences as the weighting coefficients in the OFDM waveforms for different transmit antennas and apply spatial filters with multiple receive antennas to divide the whole swath into multiple subswaths, and then, each subswath is reconstructed/imaged using our proposed IRCI-free range reconstruction method.