Wideband Bandstop Filter Based on Capacitively Coupled λ/4 Short-Circuited Lines

Duong, Thai Hoa; Kim, Ihn-Seok

doi:2010.10.3.92

J. Electromagn. Eng. Sci > Volume 10(3); 2010 > Article

Journal of the Korean Institute of Electromagnetic and Science 2010;10(3):92-98.
DOI: https://doi.org/10.5515/JKIEES.2010.10.3.092

Wideband Bandstop Filter Based on Capacitively Coupled λ/4 Short-Circuited Lines

Thai Hoa Duong¹, Ihn-Seok Kim²

¹University of Melborn
²College of Electronics & Information, Kyung Hee University

Abstract

A new wideband bandstop filter(BSF) with a sharp roll-off characteristic is introduced in a stripline structure in this paper. The BSF consists of two sections: the first is two capacitively coupled $lambda/4$ short-circuited lines with opposite ground positions, while the second is a capacitively coupled $lambda/4$ short-circuited line. The BSF provides three transmission zeros within the stopband and better than 22 dB rejection over the whole wireless local area network (WLAN) band from 5.15 to 5.825 GHz. The BSF, cascaded to an U.S. ultra-wideband(UWB: 3.1~10.6 GHz) band-pass filter(BPF), is simulated with HFSS and realized with low-temperature co-fired ceramic(LTCC) green tape with a dielectric constant of 7.8. The measurement results agree well with the HFSS simulation results. The size of the UWB BPF including the BSF is $3{times}6.3times0.45;mm^3$.

Key words: Ultra Wideband(UWB), Bandpass Filter(BPF), Wireless Local Area Network(WLAN), Bandstop Filter(BSF), Capacitive Coupling, Capacitively Coupled $\lambda/4$ Short-Circuited Lines, Low-Temperature Co-fired Ceramics(LTCC)