A miniaturized bandpass filter with low passband insertion loss and high harmonic suppression in ultra-wide stopband

• Main Authors: Cui, Lan, Wu, Wen, Shen, Zhongxiang, Fang, Dagang
• Other Authors: School of Electrical and Electronic Engineering
• Format: Article
• Language: English
• Published: 2015
• Subjects: DRNTU::Engineering::Electrical and electronic engineering::Applications of electronics
• Online Access: https://hdl.handle.net/10356/104396; http://hdl.handle.net/10220/24607; http://www.scholarmate.com/scmwebsns/publication/view;jsessionid=6068753C0735F64345F348015AAB459E.bjsnsweb134?des3Id=bdge2VxvGiN3Gbbw1%252FCJBA%253D%253D
• Institution: Nanyang Technological University

This paper presents a novel 2.4GHz Chebyshev bandpass filter that exhibits low insertion loss in the passband and high harmonic suppression in ultra-wide stopband. Asymmetric compact microstrip resonant cells combined with a shunt open-circuited microstrip line are employed as admittance inverters instead of the traditional quarter-wavelength lines to suppress the second, third and fourth harmonics in the upper bands. Folded lines are used to realize the half-wavelength shunt open-circuited stubs to achieve a size reduction and performance improvement. By introducing a new optimization strategy, the filter can be efficiently optimized by separately optimizing the resonant cells and folded lines. Measured results show very good performance with a low insertion loss of 0.69dB and return loss of 30.5dB at the center frequency with 0.01dB equal-ripple bandwidth of 5%. The ultra-wide stopband is from 3.37GHz to 9.88GHz, where harmonics up to the fourth order are highly suppressed.