High accuracy unambiguous angle estimation using multi‐scale combination in distributed coherent aperture radar

Distributed coherent aperture radar (DCAR) can realise N 3 times signal‐to‐noise ratio promotion, as well as achieve high accuracy angle estimation since it has an equivalent large aperture. However, due to its sparse array, grating lobes are emerged in antenna pattern, which will lead to ambiguous angle estimation. Based on the various degrees of freedom of DCAR, this study proposes a multi‐scale combination method to disambiguate the correct angle from the ambiguous ones. Firstly, it combines the antenna in different scale, so each combination has different equivalent phase centre spacings. Secondly, phase comparison monopulse is employed to measure the angles under each combination with relatively low computational complexity, even in the single snapshot scenario. Thirdly, the high accuracy unambiguous angle can be resolved from the low accuracy unambiguous angle step by step. Moreover, the estimation accuracy and design criterion on correct angle extraction are also analysed, providing an array geometry and combination design approach to guarantee the disambiguity process a success. Finally, DCAR with two radars and eight radars are properly designed, respectively, and simulations and field experiments validate the effectiveness of the proposed method.