EXTRACTION OF SCATTERING MATRIX COEFFICIENTS OF NRD AND WAVEGUIDE DISCONTINUITIES BY THE TLM METHOD

NRD has received considerable attention due to its low loss nature and the ability to suppress radiation at bends and discontinuities. It is proposed to exploit the above properties to design a NRD based slot arra y. Previous work relied on measured data for the admittance of a single slot in the ground plane of the NRD. In this paper, a single slot in the NRD ground plane is characterised using th e TLM method. The perfectly matched layer (PML) Absorbing Boundary Condition was used to ensure minimal reflection from the exterior boundaries of the computational domain. It is also shown that a s11 of -40 dB is achieved when the PML is used to terminate the NRD. Modal decomposition was used to determine the scattering parameters for a discontinuity in a rectangular waveguide in the presence of evanescent modes. Results obtained were found to be in close agreement to those in the literature. Currentl y, this method is being extended to evaluate the s11 of the slot on the ground plane of the NRD.