Double-Layer Structure of Rectangular-Waveguides for Butler Matrix

The authors propose a novel double-layer structure of rectangular waveguides for Butler matrix. The waveguide Butler matrix is expected to be used with a multibeam antenna in mobile communications at frequencies higher than 5GHz. The double-layer structure is constructed by use of hybrids and phase shifters with broad-wall slot coupling. The required amount of phase shift is controlled by the length of the slot. A phase shifter is designed and manufactured at 8.45GHz and 45-degree delay is confirmed. A 4-beam Butler matrix has been constructed and the desired phase difference between adjacent output ports is obtained at the design frequency as expected.