Coherent synthesis sparse aperture radar with grating lobes suppressed using frequency MIMO technique

Coherent synthesis sparse aperture array radar can provide a long baseline with narrower beamwidth at the cost of grating lobes. In this paper, we propose a method to suppress grating lobes based on frequency MIMO technique. By transmitting M orthogonal waveforms with diverse frequencies from subaperture-to-subaperture, M beams can be formed with the same mainlobe direction. However, grating lobes would move to different locations relative to the frequency offset Deltaf. Coherent combining the M beams would suppress grating lobes to a certain level. It is shown that the combined beam using frequency MIMO array is periodically scanning in range and angle. We further analyze the relationship of scanning period with frequency offset Deltaf and sparse distance L .