A two step incoherent signal subspace averaging to mitigate multipath due to propeller scattering

A two-step incoherent signal subspace averaging technique is applied to locate the sonobuoy in the presence of a highly coherent environment generated by the scattering of the sonobuoy signals from the aircraft propellers. The proposed technique is based on the assumption that accurate modeling of the scattering modulation effects of the propellers is available. This information gives insights into the relative contributions of the direct and multipath components to the signal subspace. The first step of the proposed technique amounts to modifying the MUSIC spectrum by projecting a weighted sum of steering vectors onto the noise subspace. The second step is to perform incoherent subspace averaging across the sonobuoy frequency channels. We show that significant improvement is achieved using the proposed technique over the case of applying noise subspace eigenstructure methods.