Reducing Excess Variance in Beamspace Methods for Uniform Circular Array

In this paper we present a procedure for reducing the excess variance introduced by beamspace transform when it is applied to uniform circular array (UCA). Several algorithms for direction of arrival (DoA) estimation exploit modal transforms which are based on the phase-mode excitation principle (D.E.N. Davies, 1983). Here we analyze the inverse Fourier series of the array impulse response, called effective aperture distribution function (EADF), for defining an efficient criterion for selecting the number of virtual array elements. The proposed criterion is optimum in the sense that maximizes the aperture of the virtual array while satisfying certain constraints on the maximum number of virtual array elements. Simulation results show that we can obtain DoA estimates with a lower variance such that they are closer to the CRB