Array signal processing using digital subarrays

Subarrays constitute a step in the direction towards full digitisation of array antennas. An overview of the problems of digital processing with subarray outputs and a description of several mitigation techniques is given. We present rules for designing subarrays, for forming sum and difference beams, clusters of scanned beams at subarray level, and for forming a guard channel. The grating effects of subarrays on adaptive beamforming and STAP are described and demonstrated by examples. Finally we describe the problems of applying superresolution methods with subarrays. (5 pages)