Analysis of multigroup and multichannel filtering properties in a ferroelectric-dielectric periodic multilayer

In this work, we propose a filter structure using a one-dimensional ferroelectric-dielectric periodic multilayer, air/[(ABA)^NC]^Np(ABA)^N/air, where N_s and N_p are the two numbers of periods. Here, B is a dielectric material of SiO₂, C is the same as B with a different thickness, and A is taken to be a ferroelectric material Ba₅₅Sr₄₅TiO₃+30%Mg₂SiO₄, whose dielectric constant is very high (ϵ=439 at 10 GHz). The results show that the transmittance spectra have N_s-channel groups at microwave frequencies and these groups can be classified into two types. The first type has only one channel group with N_p narrower channels. The other has N_s-1 groups, each of which has N_p+1 broader channels. In this filter structure the group number and channel number of each group can be determined simply by changing N_s and N_p.