Frequency dependence of power and attenuation constant in uniform waveguides

In uniform waveguides, power is a function of frequency and of an undetermined constant (the generator is at infinity). If the power is calculated by the classical method of the electromagnetic field components, with the longitudinal component as reference, the result may be wrongly interpreted. Power should be expressed rather through a reference transversal component, different in nature from the axial one. The variation of power with frequency results from the projection of the Poynting vector of the plane waves, which represents the field in the waveguide, on the longitudinal (propagation) axis. The power loss through the Hz component decreases with frequency.