Comparison of equivalent circuit models for a multimode dielectric resonator absorber

Two equivalent circuit models for a dielectric resonator absorber structure are developed and compared. The first model is based on the modal field distributions inside the resonator structure, while the other one is based on the modification of Foster's reactance theorem. Circuit parameters of these models are extracted using a genetic algorithm. The input impedance magnitude and reflection coefficient from these circuits are compared with the results from full-wave simulation within the frequency range of 3 GHz - 18 GHz. It is shown that the equivalent circuit using modal field distribution has a higher mean deviation for both input-impedance magnitude and reflection coefficient than that based on the Foster equivalent circuit. But, from a physical point of view, the modal field distribution offers a better explanation for the generation of modes within the resonator. Both models can complement each other.