Abstract
Medium pulse repetition frequency (MPRF) is an important mode in airborne radar system. Since MPRF mode brings both Doppler and range ambiguities, it causes difficulty for the airborne radar to suppress ground or sea clutter. In recent years, it has been pointed out that the frequency diverse array (FDA) radar is capable of separating the range ambiguous clutter, which is helpful for the airborne radar in detecting weak moving targets originally buried in ambiguous clutter. To further improve the ambiguous clutter separation performance, an enhanced pre-STAP beamforming for range ambiguous clutter suppression is proposed for the vertical FDA planar array in this paper. With consideration of range dependence of the vertical spatial frequency, a series of pre-STAP beamformers are designed using a priori knowledge of platform and radar parameters. The notches of the beamformers are aligned with the ambiguous clutter to extract echoes from desired range region while suppressing clutter from ambiguous range regions. The notches can be widened by using covariance matrix tapering technique and the proposed method can improve the performance of range ambiguous clutter separation with limited degrees-of-freedom (DOFs). Simulation examples show the effectiveness of the proposed method.
Highlights
Space-time adaptive processing (STAP) jointly explores multiple channels and several pulses to discriminate target from clutter and jamming in the spatial-temporal domain, which has found wide applications [1,2]
It is pointed out that the frequency diverse array (FDA) radar is capable of separating the range ambiguous clutter, which is helpful for the airborne radar in detection of weak moving targets originally buried in ambiguous clutter
A per-STAP beamforming method is devised for the vertical-FDA radar system to handle the range ambiguous echoes separation issue in the medium pulse repetitive frequency (MPRF) mode
Summary
Space-time adaptive processing (STAP) jointly explores multiple channels and several pulses to discriminate target from clutter and jamming in the spatial-temporal domain, which has found wide applications [1,2]. Radar working in MPRF mode usually comes up with the range ambiguity problem which makes the nonstationarity of clutter even worse In this case, the near-range and far-range regions would be illuminated by the same transmit pulse beam, the corresponding echoes are collected in different pulses but overlapped due to the limited pulse repetition interval. We further explore the pre-STAP beamforming method for the vertical FDA radar by using a priori knowledge of platform and radar parameters, including the frequency repetitive frequency, maximum detectable range, height of platform, carrier frequency, array configuration et al It is possible to construct the power spectrum in elevation frequency domain even before collecting the radar echo. The pre-STAP beamformer can form notches to suppress the range ambiguous clutter with limited DOFs in the elevation dimension.
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