Analysis of NRD waveguide-based components and transitions using the TLM-based modal extraction approach

Abstract

This paper presents a full-wave modal analysis of several typical components based on a nonradiative dielectric (NRD) waveguide technology using the transmission line matrix (TLM)-based modal extraction approach (TMEA) for the first time. It also presents a full-wave analysis of a slot-coupled microstrip-to-NRD waveguide transition, evaluating the modes excited in the NRD waveguide. The components studied using this approach include a two-pole air gap-coupled NRD-waveguide bandpass filter. an LSM-LSE mode transducer and an open-ended NRD waveguide. Previous study of these components focussed only on the LSM01 mode. Also, die only previous work investigating a slot-coupled microstrip-to-NRD geometry while taking into consideration the modes propagating in the NRD waveguide used the high-frequency structure simulator to model the transition. It is shown in this work that the TMEA can be extended to perform a rigorous modal analysis of NRD waveguide-based components and the microstrip-to-NRD waveguide transition, taking into account all propagating modes in the NRD waveguide. Results obtained using this method have been verified using the power conservation theorem and the Poynting theorem. The results show for the first time that nonorthogonal leak-age can complicate the performance of certain NRD waveguide-based components like the LSM-LSE mode transducer.