Mode Filtering with a Small Horizontal Line Array

Mode filtering is a key procedure in passive localization or source depth discrimination. Since the horizontal line array (HLA) lacks sampling of modes in depth direction, the orthogonality of modes can't be utilized in mode filtering with a HLA. Thus, the mode filtering with a HLA, especially with a small HLA is generally a difficult problem. In this paper, we focus on the mode filtering with a small HLA, which can be applied to the passive localization or source depth discrimination with a small HLA. Firstly, the pressure received on the HLA is describe by normal mode model, and several classical mode filters are introduced. Then considering the modal amplitudes are corresponding to the wavenumbers, we regard the mode filtering as generalized beamforming, which is performed in the wavenumber domain. Through constraining the maximum side lobe minimum, the modal amplitudes are beamformed. Finally, the performance of the proposed mode filter is evaluated relative to other methods in Monte Carlo simulation.