Planar orthogonal mode transducer based on orthogonal LSM10 and TE10 modal fields of co-layered image SINRD (iSINRD) and SIW guides

The field orthogonality of LSM₁₀ and TE₁₀ modes respectively in connection with image SINRD (iSINRD) guide and SIW is exploited to develop a planar millimeter-wave hybrid orthogonal-mode transducer (OMT) within the same dielectric substrate layer. The two output arms are related to an iSINRD guide and an SIW. The proposed co-layered planar OMT belongs to a narrowband acute angle class. The design process is explained and measurements at 94 GHz are presented. No septa or step changes in thickness are required. Both modes are excited using WR10 transitions where the transition of one mode is orthogonal to the other. Therefore, the OMT is fabricated as a back-to-back 4-port OMT; two inputs and two outputs for each mode respectively. The lateral dimensions of all branching arms are 0.6×0.635 mm². An insertion loss of around 1.2 dB is obtained for both LSM₁₀ and TE₁₀ modes, while isolation better than 17 dB is obtained for both modes (30 dB for the LSM₁₀ mode).