Simple computation of the coupling coefficient due to a rectangular current loop for loaded circular cavities

A simple method is described to compute the coupling coefficient due to a rectangular loop in a circular cavity that may be loaded with a dielectric resonator. The resonant frequency and the unloaded Q-factor are computed from the modal solution without the presence of the loop. An equivalent circuit is obtained for the unloaded cavity and the loop coupling is represented by a series inductance. As an example the resonant frequency (f₀), unloaded Q-factor (Q₀) and the coupling coefficient (K) for a dielectric resonator (DR) placed in a parallel plate cavity are computed. The measured input impedance of the parallel plate resonator is in good agreement with computed values