Abstract
Mainbeam jamming poses a particularly difficult challenge for conventional monopulse radars. In such cases spatially adaptive processing provides some interference suppression when the target and jammer are not exactly coaligned. However, as the target angle approaches that of the jammer, mitigation performance is increasingly hampered and distortions are introduced into the resulting beam pattern. Both of these factors limit the reliability of a spatially adaptive monopulse processor. The presence of coherent multipath in the form of terrain-scattered interference (TSI), although normally considered a nuisance, can be exploited to suppress mainbeam jamming with space/fast-time processing. A method is presented offering space/fast-time monopulse processing with distortionless spatial array patterns that can achieve improved angle estimation over spatially adaptive monopulse. Performance results for the monopulse processor are obtained for mountaintop data containing a jammer and TSI, which demonstrate a dramatic improvement in performance over conventional monopulse and spatially adaptive monopulse.
Highlights
A tracking radar requires a high-precision angular measurement of a target’s azimuth which is traditionally achieved using monopulse processing
Distortions introduced by the jammer signal into the sum and difference beams are evident, in particular, the common null at 3◦ that manifests itself as a singularity in the monopulse response curve (MRC)
An evaluation of the new SFT monopulse concept is conducted on experimental dataset mmit004v1 containing a direct-path barrage noise jammer at 32◦ and stationary terrain-scattered interference (TSI) collected as part of the DARPA/Navy Mountaintop Program [11, 12]
Summary
A tracking radar requires a high-precision angular measurement of a target’s azimuth (or elevation) which is traditionally achieved using monopulse processing. The proposed approach is not offered as a competing approach to existing STAP monopulse techniques, but rather, as a treatment of the specific problem of angle estimation when either TSI alone or mainbeam jamming together with TSI corrupt the sampled returns. In such scenarios slow-time STAP by itself is of limited benefit since the sparsely spaced coherent samples offer little benefit in predicting and subsequently mitigating the direct path mainbeam jammer signal from its scattered multipath. By the same token the proposed approach depends on the presence of strong TSI in the returns, without which the incorporation of fast-time taps is of little or no benefit for mainbeam jammer cancellation
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