2. Static and dynamic analysis

Basically, when we talk about lines (or cables), we're referring to Transverse ElectroMagnetic (TEM) operation, a mode for which we can univocally define a line voltage and current, as well as its characteristic impedance. The latter can be calculated simply using electrostatic theory, which often requires numerical calculation techniques. Consequently, dynamic field theory is not required to describe the phenomena of propagation and reflection at the ends, since these are governed by the telegrapher's equations (line theory).

This simplified model can be used even in structures where, theoretically, TEM mode cannot exist (heterogeneous structures). This is referred to as quasi-TEM operation. Under certain conditions, the microstrip line is an example where, in a certain frequency band, the longitudinal field components are very small compared to the transverse...