Design of V Band 4×4 Butler Matrix in Ridge Gap Waveguide Technology

This paper presents a Butler matrix in Ridge Gap Waveguide (RGW)technology. For this purpose, we first design the riblet coupler in the millimeter wave band. The riblet coupler is designed with a coupling coefficient of 3 dB and a phase difference of 90 degrees at the outputs. Also, the return loss of all ports of this coupler in the frequency range of 53-60 GHz is better than 10 dB. Then we design a crossover and 45-degree phase shifter in the mentioned frequency range. By integrating four ribelt couplers, two phase shifters and a crossover, the Butler matrix structure is formed. The designed Butler matrix has 4 input and 4 output ports. The simulasion results of the designed matrix obtained by HFSS software show that for excitation of each input port in the frequency range of 53-60 GHz, the power is divided approximately equal between 4 output ports with a ratio of about -6 dB. But there is a linear phase difference between the matrix output ports, which also the phase of output ports change as the excitation port changes to other port. The simulation results are valid due to the desired amplitude and phase distribution at the matrix outputs. Also, comparing the results with those obtained by CST software confirms the proper performance of the designed matrix..