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International Journal of Antennas and Propagation
Volume 2018, Article ID 9029240, 6 pages
Research Article

Design of a Suspended Stripline Narrow Bandpass Filter with Ultrawideband Harmonic Suppression

School of Electronics Engineering, Kyungpook National University, 80-Daehak-ro, Buk-gu, Daegu 41566, Republic of Korea

Correspondence should be addressed to Kang Wook Kim;

Received 16 November 2017; Revised 14 February 2018; Accepted 28 February 2018; Published 5 April 2018

Academic Editor: Chien-Jen Wang

Copyright © 2018 Ju Seong Park et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


A design method of narrow bandpass filters (NBPFs) of 4–6% bandwidth with ultrawideband suppression of harmonic passbands, utilizing two cascaded step impedance resonators (SIRs) in a suspended stripline, is proposed in this paper. The proposed design utilized the characteristics of a suspended stripline, which provides a much higher characteristic impedance ratio as compared with that of the microstripline, enabling ultrawideband harmonic suppression. As an example of the NBPF, a filter with a passband center frequency of 0.75 GHz and bandwidth of 5% was implemented and proved to suppress the harmonic passbands up to . Since the proposed filter was implemented on the suspended stripline, the passband insertion loss was only −0.9 dB, which is low as compared with other previous designs. The proposed filter is a compact high-performance low-loss NBPF, which can be applicable to various wireless systems.