SOLUTION OF SOME MICROWAVE WAVEGUIDE DISCONTINUITY PROBLEMS

Abstract

The solution of a number of waveguide discontinuity problems of practical interest is presented in this thesis. These include the longitudinal discontinuities in the shielded microstrip line and the transverse discontinuities in the waveguide Junctions and waveguide antennas. Various method of solutions are used: the modal analysis, the singular integral equation method, the spectral domain analysis and the method of moments. To obtain accurate results, the edge condition of the electromagnetic fields at the plane of discontinuity is taken into account explicitly in each case, by using various basis functions such as the Chebyshev, Gegenbauer and Jacobi polynomials. For the modal analysis method which has a slow convergence pattern, a nonlinear transformation is applied to improve the accuracy of the results. Using variational methods, more accurate closed-form formulae for the capacitance are derived for the shielded microstrip line and the 2-to-1 E-plane junction with mixed dielectrics. Wherever possible, experimental verification of the salient theoretical results has been carried out for the structure analysed. The appropriate Jacobi polynomial basis functions have also been utilised to study the characteristics of a two-dimensional version of a compact antenna such as the waveguide excited short backfire antenna.