An Orthogonal Waveform for MIMO-SAR Applications

Abstract

Synthetic aperture radar (SAR) with multiple transmit and receive channels (MIMO-SAR) has a higher flexibility and an improved efficiency compared to a conventional SAR system with a single channel. The multiple receive channels can be used, among other things, to increase the swath width at constant azimuth resolution or to suppress spatial interferences. However, multiple transmit channels, which transmit simultaneously in the same frequency band provide currently a challenge. The generation of a waveform which is orthogonal for surface scatterers, proves to be excluded with conventional methods. Therefore, in this paper a modified Chirp wave-form is introduced which extends in combination with digital beam-forming (DBF) on receive the orthogonality condition to another degree of freedom, thus allowing perfect orthogonality. Furthermore, the hardware design of the MIMO-Radar Demonstrator, a multi-channel measurement system for radar and SAR applications is shown. This at the German Aerospace Centre developed system allows the metrological verification of the waveforms presented in this paper, and other innovative concepts for future spaceborne Earth observation missions.