Design of a wideband transition between coaxial probe and parallel-plate waveguide

• Main Author: Shen, Junfei.
• Other Authors: Shen Zhongxiang
• Format: Final Year Project
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::Electrical and electronic engineering::Antennas, wave guides, microwaves, radar, radio
• Online Access: http://hdl.handle.net/10356/54421
• Institution: Nanyang Technological University

This final year project contains two designs. The first one is the design of a wideband transition between coaxial probe and parallel-plate waveguide. The second is the design of coaxial to water-layer transition. Both designs have been structured and simulated using High Frequency Structural Simulator. The wideband coaxial-to-radial transition has been fabricated to verify the design concept. Simulated and tested results are presented and discussed in the report. The first part of the report is about the design of a wideband coaxial to radial transition. It consists of two stages. The first stage focuses on a simple coaxial to parallel-plate waveguide transition. The effects of variation of various parameters of the transition structure on the return loss are studied. The values of those parameters are adjusted to achieve the best return loss with widest bandwidth. The overall -10dB return loss covers a bandwidth of 2.46 GHz to 15 GHz. The second stage adds a horn-shaped waveguide on one side of the original parallel-plate waveguide in facilitating the characterization of frequency selective surface. The values of parameters of the horn-shaped waveguide are further adjusted to achieve best performance that the resulting overall -10dB return loss covers an even wider bandwidth of 2.0 GHz to 15.0 GHz. The second part of the report is the design of a coaxial to water-layer transition, which uses water instead of air as transmission medium in the waveguide. A dielectric material is added around the center conductor in order to ease microwave transmission between two mediums having greatly different relative permittivity. The structure of dielectric material is adjusted to get an overall -5dB return loss covering 1.11 GHz to 1.4 GHz on the low frequency side, 2.4 GHz to 15 GHz on the high frequency side. Further design is needed to achieve better return loss.