Title :
Tunable microstrip lowpass filter with compact size and ultra-wide stopband
Author :
Chuantao Cai ; Jianpeng Wang ; Gang Zhang
Author_Institution :
Ministerial Key Lab. of JGMT, Nanjing Univ. of Sci. & Technol. (NUST), Nanjing, China
Abstract :
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.
Keywords :
UHF diodes; UHF filters; UHF resonators; band-stop filters; circuit tuning; coupled circuits; low-pass filters; microstrip filters; ultra wideband technology; varactors; compact size; compact varactor-tuned microstrip LPF; cut-off frequency tuning range; frequency 0.85 GHz to 2.28 GHz; low-impedance stub; parallel coupled-line; radial patch resonator; stepped-impedance resonator; tunable microstrip lowpass filter; ultrawide stopband; varactor diode;
Journal_Title :
Electronics Letters
DOI :
10.1049/el.2015.0829