Abstract
A method based on frequency diversity to suppress grating lobes in coherent MIMO radar with separated subapertures is proposed. By transmitting orthogonal waveforms from separated subapertures or subarrays, receiving beams can be formed at the receiving end with the same mainlobe direction. However, grating lobes would change to different positions if the frequencies of the radiated waveforms are incremented by a frequency offset from subarray to subarray. Coherently combining the beams can suppress or average grating lobes to a low level. We show that the resultant transmit-receive beampattern is composed of the range-dependent transmitting beam and the combined receiving beam. It is demonstrated that the range-dependent transmitting beam can also be frequency offset-dependent. Precisely directing the transmitting beam to a target with a known range and a known angle can be achieved by properly selecting a set of . The suppression effects of different schemes of selecting are evaluated and studied by simulation.
Highlights
Unlike a traditional phased-array radar system, which can only transmit scaled versions of a single waveform, a multi-input multi-output (MIMO) radar system has shown much flexibility by transmitting multiple orthogonal waveforms [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]
The method to suppress grating lobes based on frequency diversity in coherent MIMO radar with separated subarrays addressed in Section 3 is evaluated by simulation
A method based on frequency diversity to suppress grating lobes in sparse MIMO aperture radar is proposed in this paper
Summary
Unlike a traditional phased-array radar system, which can only transmit scaled versions of a single waveform, a multi-input multi-output (MIMO) radar system has shown much flexibility by transmitting multiple orthogonal (or incoherent) waveforms [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]. One class is noncoherent processing to overcome the radar cross section (RCS) fluctuation of the target [1,2,3]. In this scheme, the transmitting antennas are separated from each other to ensure that a target is observed from different aspects. It is demonstrated that by phase synchronizing across the sparse antennas, the resolution of MIMO radar can be improved to the level of the carrier wavelength λ0. The statistical analysis of sidelobes in coherent processing sparse MIMO radar with randomly positioned antennas has been studied in [18]. By coherently combining the receiving beams formed at different frequencies, the grating lobes can be suppressed or averaged to a low level.
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