Nonadaptive MIMO radar techniques for reducing clutter

Multiple-Input, Multiple-Output (MIMO) radars enhance performance by transmitting and receiving coded waveforms from multiple locations. This paper describes how MIMO techniques can be used to improve radar performance, especially in airborne GMTI applications. A previous analysis of the clutter-to-noise-ratio (CNR) for stationary, surface-based MIMO radar is extended to the airborne radar scenario. Our analysis shows that MIMO airborne radars will have lower CNRs, resulting in smaller losses when observing stationary and low-velocity targets. We also address the implementation of MIMO radar modes using Electronically Scanned Arrays (ESAs). Herein, we show that implementing MIMO techniques within a subarrayed antenna can result in high sidelobes and/or reduced search rates. To address this problem, we describe how space-time waveform coding can be used to improve performance. Two space-time waveform encoding approaches are proposed: (1) an overlapped virtual transmit subarray approach, and (2) a beamspace MIMO processing approach. A third approach, involving conventional MIMO waveforms and irregular subarrays, is also briefly considered.