Open AccessTunable microstrip lowpass filter with compact size and ultra‐wide stopband
Author(s) -
Cai Chuantao,
Wang Jianpeng,
Zhang Gang
Publication year - 2015
Publication title -
electronics letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.375
H-Index - 146
ISSN - 1350-911X
DOI - 10.1049/el.2015.0829
Subject(s) - stopband , varicap , cutoff frequency , microstrip , low pass filter , transition band , materials science , elliptic filter , resonator , optoelectronics , passband , electronic engineering , prototype filter , acoustics , filter (signal processing) , band pass filter , physics , capacitance , electrical engineering , engineering , electrode , quantum mechanics
A compact varactor‐tuned microstrip lowpass filter (LPF) with a large cutoff frequency tuning range and an ultra‐wide stopband is presented. By employing a pair of parallel coupled‐lines and a low‐impedance stub loaded with a varactor diode, the introduced filter can successfully realise the tunable cutoff frequency function. Besides, both radial patch resonators and stepped‐impedance resonators are introduced to achieve an ultra‐wide stopband in all the states in this design. A varactor‐tuned microstrip LPF is designed, fabricated and measured. The measured results show that the proposed LPF provides not only a large cutoff frequency tuning range of 91.3% from 0.85 to 2.28 GHz, but also an ultra‐wide stopband which extends to 20 GHz.