X-Band Multilayer Butler Matrix and SIW Multi-Beam Antenna: Analysis and Design

This article presents a new Butler matrix made on stacked Printed Circuit Boards (PCBs). The matrix is based on Substrate Integrated Waveguides (SIW) and microstrip lines. Transitions using through metallic vias are designed and optimized for the crossover sections of the matrix. The other components of the circuit are as follows: 3-dB SIW directional coupler, 45 degrees phase-shifter, and SIW dual-slot linear antenna array. Different sections of the matrix were simulated, fabricated, and tested. Using the full structure with radiating elements, we obtained good numerical and experimental results in terms of radiations patterns for the different beam directions, impedance matching, and isolation between the input ports.