Electromagnetic analysis of tunable bandpass filters with a magnetodielectric perturber

Electromagnetic (EM) analysis is performed for a tunable bandpass filter with a magnetodielectric perturber controlled by a piezoelectric transducer. The structure includes a perturber as a superstrate which consists of thin ferrite film with a high permeability and Rogers dielectric material with a high permittivity in a sandwich style. The structure is of multiscale feature because the thickness of the thin film is very small but cannot be ignored. The problem can be solved by surface integral equations (SIEs) in the integral equation approach, but the conditioning of system matrix may not be good. We use volume-surface integral equations to formulate the problem in this work and the disadvantage of SIEs can be overcome. A numerical example is presented to illustrate the approach.