Causality and waveguide circuit theory

We develop a new causal power-normalized waveguide equivalent-circuit theory that, unlike its predecessors, results in network parameters usable in both the frequency and time domains in a broad class of waveguides. Enforcing simultaneity of the voltages, currents, and fields and a power normalization fixes all of the parameters of the new theory within a single normalization factor, including both the magnitude and phase of the characteristic impedance of the waveguide. Enforcing simultaneity also ensures that the theory´s voltages and currents do not start before their excitation, and that the network parameters of passive devices are causal, a necessary condition for stable time-domain simulations