Beamforming of coherent signals for weighed two concentric ring arrays

The Davies transformation is a method to transform the steering vector of a uniform circular array (UCA) to one with Vandermonde form, which allows techniques such as spatial smoothing in a correlated signal environment. However, the Davies transformation, applied to the beamforming of coherent signals, will introduce strong frequency-dependent noise warping. This paper proposes a method of weighing virtual array of two concentric ring arrays to avoid such problem. Such technique is able to improve the output SNR. The effectiveness of the method is illustrated through a number of numerical examples.