Cost Effective Butler Matrix-Based Digital/Hybrid Antenna Array Architecture with Element Tapering

Fully digital beamformers present complexity, power, and cost challenges, making hybrid architectures practical alternatives for sensing, radar, and communications. By replacing analogue phase shifters with an analogue beamformer, like a low-cost, passive Butler matrix (BM), costs can be reduced by about 75% when compared to a fully digital equivalent. A new architecture as newly proposed in the following paper, builds on this by integrating BM-based sub arrays with fully digital ones. Moreover, by placing digital sub arrays at the centre of a larger array and where amplitude excitation can be programmable, enhanced pattern control and reduced sidelobe levels (SLLs) are possible when compared to traditional hybrid beamformers. Despite the standard limitations of BMs, amplitude tapering still remains effective for lowering SLLs, as demonstrated in a 16-element array with two digital and two BM-based subarrays, achieving SLLs below −10 dB over a 90-degree steering range. By including such hybrid sub arrays and with digital hardware as well as the appropriate beamforming algorithms, radiation performances can be maintained while keeping costs, complexity, and power consumption manageable and competitive.