BROADBAND BANDPASS FILTER USING PARALLEL-COUPLED MICROSTRIP LINE AND COUPLED OPEN STUB RESONATOR

摘要

A novel broadband bandpass filter with multiple resonant modes based on parallel-coupled microstrip line is proposed. The required cutoff frequency and out-of-band performance are achieved by placing L-shaped capacitive cross-coupling open stubs at the middle resonator with appropriate dimensions. A compact broadband bandpass filter of dimensions 18×29 mm~2 is fabricated and tested for performance confirmation. The proposed filter demonstrates a wide bandwidth (from 3 to 7 GHz), as well as excellent out-of-band performance with more than 25-dB rejection up to more than 12 GHz and sharp upper cutoff frequency due to the proper location of two transmission zeros.