Open AccessCompact low‐pass filters with deep and ultra‐wide stopband using tri‐ and quad‐mode resonators
Author(s) -
Li Qun,
Zhang Yonghong,
Li Daotong,
Xu Kaida
Publication year - 2017
Publication title -
iet microwaves, antennas and propagation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.555
H-Index - 69
eISSN - 1751-8733
pISSN - 1751-8725
DOI - 10.1049/iet-map.2016.0466
Subject(s) - stopband , resonator , transition band , cutoff frequency , passband , band pass filter , microstrip , low pass filter , electronic engineering , multi mode optical fiber , materials science , optoelectronics , physics , acoustics , filter (signal processing) , optics , prototype filter , engineering , electrical engineering , optical fiber
On the basis open stub‐loaded tri‐ and quad‐mode resonators, two compact microstrip low‐pass filters (LPFs) with deep and ultra‐wide stopband are presented. Modal characteristics of the tri‐ and quad‐mode resonators are analysed by even–odd‐mode method. Multimode resonator can be modelled as multiple LC resonant circuits and the lumped‐element equivalent circuit models of the proposed LPFs are presented. The tri‐ and quad‐mode resonators have strong slow‐wave and bandstop effects, which can achieve ultra‐wide and deep stopband and size reduction in the design of LPFs. For the proposed low‐pass filter using tri‐mode resonators, the 3 dB cutoff frequency is 2.5 GHz and the stopband with 40 dB suppression is from 4.5 to 17.7 GHz. The low‐pass filter based on quad‐mode resonators has a 3 dB cutoff frequency of 2.2 GHz and the stopband with 30 dB suppression is from 4.1 to 18 GHz.