Synthesis of an artificial high effective permittivity medium in a SIW periodically loaded with metallic cylinders

Recently, a new topology of step-impedance bandpass filters in Substrate Integrated Waveguide (SIW) technology has been theoretically and experimentally demonstrated in which the high impedance regions, i.e., those with low effective permittivity, have been achieved by inserting air holes to lower the substrate permittivity. Going a step further, in this work we propose a different way to obtain a high-low permittivity step in a SIW, by increasing the relative permittivity in some regions. This can be practically achieved by inserting in the dielectric an array of metallic inclusions. This paper presents the results of a systematic study of the effective permittivity in a SIW in which arrays of metallic cylinders are added along the waveguide in order to synthesize a higher effective permittivity. The study has been performed with the commercial software tool Ansys High Frequency Structural Simulator (HFSS). The results of this study will be used in a new topology of bandpass filters in SIW technology based on coupled cavities of different permittivity, achieved by the introduction of metallic cylinders in the higher permittivity sections and air holes in the lower ones.