COMPUTER AIDED DESIGN OF WAVEGUIDE FILTERS USING THE MODE MATCHING METHOD

Abstract

Modern satellite and terrestrial telecommunication systems usually employ a large number of waveguide filters, operating at microwave frequencies. Traditionally, waveguide filters are designed empirically using approximate discontinuity models and extensive bread-boarding. Over the last two decades, the demand for accurate analysis and design techniques has generated a tremendous output of numerical methods for microwave applications. The mode matching method, based on a combined field theory and modern network theory approach, is a powerful technique for solving waveguide discontinuity problems which are inherently present in waveguide filter structures. With the advent of powerful computers and workstations, field theory based models became desirable tools for computer aided design of waveguide filters. In this thesis, complete computer aided design methods for waveguide bandpass and low-pass filters are developed. Several existing filter structures are designed and new filter structures with better performance characteristics are proposed. The results obtained are verified using experimental and published results. With the computer aided design method developed in this thesis, waveguide low-pass and bandpass filters at microwave frequencies can be designed accurately without bread-boarding and post-production tuning of the designed filters. The design process in mass production of the microwave waveguide filters can be greatly simplified with the use of the computer aided design method developed.