Subarray Design Diagnostics for the Suppression of Undesirable Grating Lobes

This paper investigates various subarray pattern distortions that can cause the appearance of grating lobes with the aim to provide an insightful and valuable first-order diagnostic tool for antenna array designers. In typical subarray configurations, the emergence of undesirable grating lobes is a possibility due to distortions in the subarray array factor which can be caused by feeding errors, mutual coupling between elements and/or feed lines, or other discrepancies. This paper will focus on systematic errors that can arise in subarray designs that feature common element excitation schemes. Distortions will be categorized by amplitude and phase errors separately, demonstrating their distinct manifestations in each excitation scheme. Recognition of these manifestations can lead to better subarray designs and save significant time in the development of large array antennas. The concepts introduced here will be supported by analytical array factor calculations for 1 × N linear subarrays, full-wave simulations of a 1 × 4 subarray and 1 × 16 array, and representative measurements of two 1 × 16 arrays at Ku-band.