Study Of Mode Matching Method And Application Under United Coordinate System

In the normal mode matching method procedure,. the modal field of the rectangle, circular, elliptical waveguide expanded in Cartesian, cylindrical and elliptical coordinate systems by trigonometric functions, Bessel functions and Mathieu functions, respectively. There two difficulties: first , one has to merge two different coordinate systems when the type of two waveguides between the waveguide discontinuity are different, and second, one has to overcome the problem of Bessel functions and Mathieu functions'convergence property.In this paper, a novel united mode matching method is introduced, using the polynomial approximation in the Cartesian coordinate system. Avoiding the complicated calculation of Bessel functions and Mathieu functions. Simplify the analytical procedure and accelerating the calculation.Also in this paper, the simulation programs for the key blocks based on mode matching method are programmed by MATLAB, and by the scattering matrix cascading technology, these program blocks can be cascaded together to form the sophisticated microwave passive components. This program gives a fast calculation speed with the same accuracy. And in this paper, a simple introduction of the properties of Mathieu function in elliptical waveguide is given. At last using the united polynomial approximation method to analyze the cutoff wave number and field distribution of different type of waveguide.