A checkered network for implementing arbitrary overlapped feed networks

Abstract

Existing overlapped subarray techniques for beamforming arrays aim to realize flat-topped subarray radiation patterns, where pattern synthesis is constrained by the hardware configuration. A generalized framework for designing compressive arrays with unconstrained feed network responses has recently been proposed with promising results, but no hardware implementation has been proposed. A planar checkered network of directional couplers and fixed phase shifters is proposed for implementing arbitrary complex-valued feed network responses, including completely overlapped networks. An algorithm is proposed for realizing a desired response while minimizing the range of coupling ratios and phase shifts required. The technique is validated by a comparison to the standard 4 x 4 Butler matrix implementation, and its versatility illustrated by sharing an eight-element aperture between three independently designed nonscanning arrays. A manufactured microstrip 2 x 4 compressive array feed network achieves the desired aperture illuminations to within 0.6 dB and 5.2° at 3.15 GHz, and to within 1.4 dB and 10.3° across the impedance bandwidth of 4.5%.