Q1Electromagnetics Waves

A rectangular waveguide is a hollow conducting metallic pipe (typically brass or copper, usually silver- or gold-plated internally) of uniform rectangular cross-section with broad dimension 'a' and narrow dimension 'b' (a > b by convention), used to confine and guide electromagnetic energy from a source to a load at microwave and millimetre-wave frequencies (roughly 1-300 GHz). Unlike two-conductor transmission lines, a waveguide has only a single hollow conductor, so it cannot support a TEM (transverse electromagnetic) wave; instead it supports an infinite discrete set of TE (transverse electric, Ez = 0) and TM (transverse magnetic, Hz = 0) modes, each with its own cutoff frequency below which that mode cannot propagate. Because it has no centre conductor, a waveguide has very low loss and can handle very high power compared with coaxial cable at the same frequency, at the cost of being bulky, rigid, and usable only above its dominant-mode cutoff frequency.