Waveguides and Resonators

This chapter presents field solutions for closed and open waveguides and the related topic of cavity resonators. It begins with a description of the method of separation of variables, which is needed for solving the wave equation. The method is then used to find the modes in rectangular and circular waveguides. The chapter discusses excitation methods for waveguides and presents 2D parallel‐plate and dielectric‐slab waveguides along with a discussion of surface‐wave fields. Waveguide filters and impedance‐matching networks often have discontinuities such as a step or an iris, and an understanding of their effects is important. The chapter summarizes approximate but highly accurate variational solutions for irises. The mode matching technique is a useful tool for analyzing waveguide discontinuities, and its application is demonstrated for a rectangular waveguide step and an iris. The chapter also describes the perturbation method for predicting resonance shifts.