Single-Layer Waveguide Circuit to control Sidelobe and Crossover Levels in Butler-Matrix Beam-Switching Antenna

The Butler matrix [1] is a beam-forming network for a multi-beam array antenna. The main-beam direction can be switched according to the input port. Conventional Butler matrix suffers from high crossover levels between adjacent main beams of -3.7dB and high sidelobe levels of -11.4dB independent on the number of ports, theoretically. In order to solve these problems, the configuration of a circuit has been proposed to control the crossover and sidelobe levels by using two-way dividers with 180-degree difference [2]. This paper presents this circuit configuration by single-layer post-wall waveguides [3] to integrate with a Butler matrix and a slotted waveguide antenna by complete single layer.