Dual-Layer Ridged Waveguide Slot Array Fed by a Butler Matrix With Sidelobe Control in the 60-GHz Band

A novel multibeam antenna based on a 4 × 4 Butler matrix with sidelobe level (SLL) control is proposed in the 60-GHz band. The SLL is controlled using a dedicated circuit composed by four 90-degree couplers with different coupling factors and several cross couplers. This dual-layer antenna is made by hollow waveguides and is assembled using diffusion bonding technique. The radiating part is a compact array of ridged waveguides designed to avoid appearance of grating lobes in the visible range for large scanning angles. The antenna field of view is ±43° with sidelobes lower than -17.5 dB over the entire scanning range. The isolation between the input ports of the Butler matrix is better than 25 dB at the design frequency of 61.5 GHz. The reflection bandwidth for VSWR <; 2 is larger than 6.5%. At the design frequency, the measured conductor losses of the antenna are estimated lower than 0.64 dB for all ports.