High Accuracy 2-D Angle Estimation Using Distributed Coherent Arrays

Due to wide beam and low angular accuracy for VHF radar, distributed coherent arrays are proposed for aperture extension and high angular accuracy, which is based on interferometric radar principles and 2-dimensional Direction Of Arrival (DOA) estimation algorithms. Coherently combining distributed subarrays results in grating lobes and angular ambiguities for the baselines greater than subarray apertures between the phase centers of the subarrays. Two-dimensional DOA estimations with high accuracy are accomplished by dual-size unitary ESPRIT algorithm for angular ambiguities resolution and the proposed azimuth-elevation pairing algorithm based on asymptotical orthogonality between signal space and noise space. Then distributed coherent arrays achieve effectively a large equivalent aperture. The threshold effect is analyzed with Method of Interval Error (MIE) and simple approximation computering methods for fillfactor threshold and SNR threshold are derived. Simulation results are presented verifying the effectiveness of the two-dimensional DOA estimation algorithm and high angular accuracy of the distributed coherent arrays.