Stripline Bandpass Filter with High Permittivity Dielectric

Miniaturized third order stripline bandpass filter (BPF) with high dielectric constant substrates εr = 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) fz1 and fz2 located on opposite sides of the center frequency f0. 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 fz1, fz2 and fo, as well as the symmetrical arrangement of fz1 and fz2 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 f0 = 1.85 GHz, BW = 100 MHz are presented.