MVDR Beam-Space Pre-Processing for Wideband Sources DOA Estimation

In practice it is an effective measure for target location both using wideband and beam-space processing. The combination of these two array signal pre-processing could improve the resolution of multi-target Direction of Arrival (DOA). However when SNR is low or intensive interferences existed on inconstant directions outside the beam coverage region, conventional beam-space pre-processing approach based on CBF is disabled on multi-targets DOA estimation. So a wideband beam-space pre-processing algorithm based on MVDR is proposed. It applies Rotational signal subspace (RSS) to focus effective data at every frequency bin on reference frequency bin. Then it uses MVDR to form multi-beam on the coverage region. The second step not only restrains intensive interferences, but also can reduce the focus error caused by the first step. Analysis shows its high resolution and anti-interference performance, especially while interferences are close to beam coverage region. Computer simulation results prove its validity.