WR-3 band butler matrix design using SU-8 photo-resist technology

A design of WR-3 band 2×2 Butler Matrix feeding a 2-element slotted waveguide antenna array is presented in this paper. The whole design is based on an SU-8 multi-layer structure, which is expected to be fabricated by metal-coated SU-8 thick resist technology [1]. Each layer of the SU-8 wafer has a thickness of 0.432mm, which matches the narrow-wall height of a WR-3 (220-325GHz) waveguide. To examine the performance of the proposed Matrix, prior to adding antennas, a simulation on the 90 degree resonator based hybrid coupler was carried out using the CST Microwave Studio [2]. The simulation results agree well with the theoretical predictions, validating the proposed design.