Sharp-rejection and ultra-wide bandstop filter with five transmission zero frequencies

• Published in: IET microwaves, antennas & propagation Vol. 8; no. 2; pp. 80 - 85
• Main Authors: Li, Lin, Wu, Qing-Hua, Zhao, Kai-Yu, Li, Jin, Wang, Ya-Ming
• Format: Journal Article
• Language: English
• Published: Stevenage The Institution of Engineering and Technology 01.01.2014; Institution of Engineering and Technology; The Institution of Engineering & Technology
• Subjects: Applied sciences; Attenuation; Bandstop filters; Bandwidth; band‐stop filters; BSF response; Circuit properties; Electric, optical and optoelectronic circuits; Electronic circuits; Electronics; Exact sciences and technology; filter bandwidth; Frequency filters; modified optimum wideband bandstop filter; modified optimum wideband BSF; Noise levels; passband insertion loss; passband performance; Rejection; sharp attenuation rates; sharp‐rejection; Skirts; stiff rejection; stopband rejection level; transmission zero frequency; ultrawide bandstop filter; ultrawide BSF; ultrawide rejection bandwidth; Ultrawideband; Wideband; wideband BSF performance; ultrawide rejection bandwidth; ultrawide BSF; BSF response; modified optimum wideband bandstop filter; passband insertion loss; sharp-rejection; ultrawide bandstop filter; sharp attenuation rates; transmission zero frequency; filter bandwidth; passband performance; wideband BSF performance; stopband rejection level; stiff rejection; modified optimum wideband BSF; band-stop filters; Performance evaluation; Wide band circuit; Optimal filter; Wide band; Simulation; Insertion loss; Compact design; Band stop filter; Passband; Impedance; Transmission zero
• ISSN: 1751-8725; 1751-8733; 1751-8733
• DOI: 10.1049/iet-map.2012.0507

This study proposes a new modified optimum wideband bandstop filter (BSF). Detailed theoretical analysis reveals that five transmission zero frequencies appear in the proposed BSF's response to compose an ultra-wide BSF with stiff rejection. Moreover, the filter's bandwidth, stopband rejection level and passband performance can be tuned flexibly by changing the impedances of the configuration. Both the simulations and measurements of the fabricated filter demonstrate good wideband BSF performance including an ultra-wide 20 dB rejection bandwidth of 140%, sharp attenuation rates more than 227.3 dB/GHz at both skirts, lower passband insertion loss less than 1.5 dB at both lower and upper passband and very compact size of λg2.