The very nature of this chapter is theoretical and investigative, mainly consisting, in the first part, of a study of the consequences of the Lorentz' reciprocity theorem as applied to closed waveguides. This part, extending up to Section 3.2, requires a bit of “mathematical technicality” - as for the entire Chapter 2 - while remaining quite abstract. Nevertheless, as the final step of an electromagnetic analysis normally involves the computer solution of some kind of equation, physical insights in the expected solution are really helpful in avoiding numerical trouble and in recognising so called “spurious solutions”. Spurious solutions, as we will see, are solutions of the numerical problem holding no physical meaning. Hence, we will derive general constraints linking propagation constant, power flow, dissipation and storage in closed, uniform waveguides loaded with linear, isotropic media. Some constraints are also derived on the frequency variation of the above quantities. In the particular case of a lossless waveguide, critical points in the characteristics and complex waves are discussed. The complex wave phenomenon in lossless media still posing some intriguing questions, is carefully investigated leading to the statement of a fundamental theorem.

Inspec keywords: waveguides

Other keywords: electromagnetic analysis; Lorentz reciprocity theorem; linear media; complex wave; isotropic media; closed waveguides; lossless waveguide

Subjects: Waveguides and microwave transmission lines