A design and fabrication of bandpass filter using miniaturized microstrip square SIR

A four-pole quasi-elliptic function bandpass filter of 1.95 GHz center frequency with 60 MHz bandwidth for IMT-2000 is designed and fabricated using the miniaturized square stepped impedance resonator (SIR). The nonuniform finite difference time domain (NUFDTD) method is used to design the resonator and to calculate the coupling coefficient of three basic structures. The size reduction of miniaturized square SIR resonator is about 50% compared with a square open loop resonator. A bandpass filter using this resonator show good microwave characteristics with harmonic suppression of about -19 dB at 4.76 GHz. The results of measurements are almost similar to those of simulation.