Incoherent Resolution of Unresolved Surface Multipath

The reflection off the ground or sea is known to produce a strong multipath signal that can be unresolvable in both angle and range from that of the direct path. While the measured range is relatively unaffected, the apparent elevation obtained from monopulse or using digital beamforming to locate the energy maxima often strongly deviates from the correct value. While means for correcting the readings using the coherent subarray or sum/difference matched filter outputs, this can prove inconvenient for retrofitting and subject to unmodeled errors, and very closely spaced reflections are in any case unresolvable with a single dwell. This paper discusses means for resolving the true elevation using only the returns (after target-associated detections) of the apparent elevation angle. Results of the technique on test data from a 5-MHz bandwidth radar at 3.35 GHz on drone targets are promising.