Spurious mode suppressing technique for performance enhancement of hybrid planar/NRD-guide circuits

A compact spurious mode suppresser for hybrid planar/NRD-guide integrated circuits is presented in this paper. The proposed mode suppressing technique with embedded metallic plate/film is used in the hybrid design that is compact and easy to implement. It is found through our investigation that the rejection of all the spurious modes (including TE and LSE modes) is better than -32 dB for a single transition of planar-to-NRD-guide over a broadband frequency of interest, and the performance could be further enhanced. This new technique also provides an alternative solution to the inherent problem of spurious modes (especially TE modes) in the standard design procedure of NRD-guide circuits.