A grating lobe suppression method for displaced subarrays using genetic algorithm

Abstract

The large-element-spacing array is often used to reduce the channels and costs of the phased array. However, it will form grating lobes (GLs) in the visible space, which decrease the performance. The displaced subarray technique has strong GL suppression ability and simple engineering implementation, but its design process is very complex. This paper presents a new parameter design method of variable subarray gaps. The gaps between subarray are optimised using genetic algorithm, and the levels of GL and quantisation lobe (QL) can be minimised simultaneously. This method sets the normalised values of gaps and the maximum gap as optimisation variables, which greatly improves the convergence speed and has strong global optimisation. In addition, a new segmented multimode horn is proposed as the array element. Its influence on GL suppression is also considered in the optimisation process. This method is used to design a prototype with 52 subarrays. The measured results show that the GL level is below −15.9 dB and the QL level is below −24 dB from 16 to 19 GHz, which are in good agreement with the simulation results. It shows that this method has a strong ability to suppress GL and QL levels for wideband applications.