Stripline Bandpass Filter with High Permittivity Dielectric

Abstract

Miniaturized third order stripline bandpass filter (BPF) with high dielectric constant substrates ε<inf>r</inf> = 92 and quasielliptic frequency response is proposed and studied. The filter uses steped-impedance resonators (SIRs), between them there are mixed couplings, which leads to the generation of two transmission zeros (attenuation poles) f<inf>z1</inf> and f<inf>z2</inf> located on opposite sides of the center frequency f<inf>0</inf>. To minimize the size of the filter, its resonators are separated from each other by small gaps of 0.2 mm. The problems of obtaining the minimum interval between transmission zeros f<inf>z1</inf>, f<inf>z2</inf> and fo, as well as the symmetrical arrangement of f<inf>z1</inf> and f<inf>z2</inf> with respect to fo are considered. The measured and simulated responses of the stripline BPF with dimensions 5.8 mm × 4.2 mm × 2 mm and parameters f<inf>0</inf> = 1.85 GHz, BW = 100 MHz are presented.