BANDPASS FILTER WITH WIDE STOPBAND USING BROADSIDE-COUPLED MICROSTRIP T-STUB/DGS CELL

摘要

A bandpass filter with wide stopband is proposed using the novel broadside-coupled microstrip T-stub/defected ground structure cells in this letter. The resonance of the proposed cell is finely adjusted. Besides, these cells with a proper coupled-structure (i.e., interdigital coupled scheme) can achieve high selectivity only around the resonance, which leads to wide stopband operation. The measured filter operated at 2.2 GHz (i.e., center frequency f_0) exhibits a wide stopband up to 9.1 f_0 with a good rejection level greater than 30.5 dB.