Multi-layered chiral filters

The use of multi-layered chiral structures as filters in the microwave frequency range is studied in this paper. These chiral devices can replace their dielectric counterparts when the synthesis of the latter has furnished values of refractive indices which are unavailable, and, in addition, they are able to rotate the plane of polarization of the transmitted wave by a given angle. These features are achieved due to the extra degree of freedom provided by the chirality admittance. The sensitivities of the two kinds of filters are calculated, analyzed and compared. The dependence of the permittivity of the medium on the chirality admittance is taken into account in order to evaluate its influence on the characteristics of the chiral filter and to compensate for it. Finally an accurate model which considers lossy frequency dependent parameters, is used to design a wide stop-band filter. The chiral filter is compared to a dielectric one: a large attenuation at the stop-band, a steep response at the cutoff frequency and a wide stop-band, are the three main advantages of the chiral filter over its dielectric counterpart.