Overview of Recent Subarray Applications in Wide-Angular Scanning Linear Arrays

Abstract

Subarray application for increasing the wide-angular scanning capability of a linear array is discussed in this paper. The original linear array is a sparse array where element locations fit in a $\lambda$/2 grid. Empty places in the grid allow for integrating small subarrays. There are two subarray configurations considered, in-line and cross-line subarrays. The in-line subarray is a 3 elements array with the extra element on the left and right sides of the center element. This subarray has been proven to compensate for the scan-loss and to suppress the sidelobes by optimizing the subarray pattern. In the optimum subarray, the phase relative to the center element equals $\Psi=\pm 140^{\circ}$ because this value gives the best trade-off between a high pattern at the direction of scanning and a null pattern in the other direction. The cross-line subarray utilizes extra elements on top and bottom of a center element in the dense part of a linear array. In the paper, we consider the case of a linear dense array with 41 elements. After sparsing and addition of phase shifters, inline subarray elements are positioned in empty places. The elements in the center part of the linear array are replaced by cross-line subarrays. When the antenna is scanned to large scan angles, this array exhibits 2.7 dB increase in directive gain, scan loss reduction of 1.3 dB and 3.9 dB lower peak sidelobe level (PSLL) compared to a uniform linear array (ULA) with the same length.