WIDEBAND BANDPASS FILTERS USING PARALLEL-COUPLED SIRS WITH WIDE SPURIOUS SUPPRRESSION

Abstract

This paper proposes parallel-coupled stepped impedance resonators (SIRs) used for wideband bandpass fllters with reduced size and improved spurious response suppression in out-of-band. The fllter design concept is demonstrated by both two- and four-parallel coupled line resonator structures with the same fundamental frequency (f0) of 6.5GHz. The flrst bandpass fllter has been designed using two resonators with ‚/2 slot and embedded slot feeds for spurious response suppression at 2f0 and 3f0, respectively. The measured insertion loss is around 0.3dB and the operation band is from 4.4 to 9.2GHz (FBW = 73.8%). For the second bandpass fllter, the embedded slot feeds and additional loaded open-stubs have been utilized to improve the wide spurious response suppression and sharp skirt characteristic in the passband. The measured passband of frequency response is from 4.2 to 8.6GHz (FBW = 67.7%). The insertion loss of passband is lesser than 0.25dB and the return loss is better than 15dB. The fllter designs are described in details. The simulated and experimental results are demonstrated and discussed.