Definitions of v, i, Z, Y, a, b, Γ, and S

Concepts and conditions underlying the establishment and use of immittance- and scattering-matrix descriptions of waveguide n-ports are discussed. TEM modes are considered and no restriction to high or microwave frequencies is implied. The discussion is intended to be critical and intensive rather than general. Needed results of electromagnetic (and waveguide) theory are assumed. Emphasis is placed on defining basic quantities needed in the matrix scheme. These include: generalized voltage and current, v and i, for waveguide modes; modal impedance; modal characteristic impedance; the immittance matrices Z and Y; traveling-wave amplitudes a and b; reflection coefficient Γ; and the scattering matrix S. Properties of Z, Y, and S are not discussed; applications are indicated but not discussed.