Stripline Bandpass Filter with High Permittivity Dielectric

Miniaturized third order stripline bandpass filter (BPF) with high dielectric constant substrates ε
_r
= 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
_z1
and f
_z2
located on opposite sides of the center frequency f
₀
. 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
_z1
, f
_z2
and fo, as well as the symmetrical arrangement of f
_z1
and f
_z2
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
₀
= 1.85 GHz, BW = 100 MHz are presented.