A super-compact wideband bandpass filter using capacitor-loaded coupled lines

Kai-Da Xu; Jing Tian; Hairui Liu; Yannan Jiang

doi:10.1515/freq-2024-0055

Article

A super-compact wideband bandpass filter using capacitor-loaded coupled lines

Kai-Da Xu , Jing Tian , Hairui Liu and Yannan Jiang

Published/Copyright: May 14, 2024

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From the journal Frequenz Volume 78 Issue 11-12

Abstract

A wideband bandpass filter (BPF) using capacitor-loaded coupled lines is proposed with super-compact circuit size and very simple structure. By loading three lumped capacitors in parallel to three same pairs of coupled lines, three transmission poles and four transmission zeros can be achieved and they can be calculated by input admittance derivation. To verify the design, a wideband BPF prototype with center frequency at 1.34 GHz is fabricated, whose measured 3-dB fractional bandwidth is 98.5 % (0.68–2 GHz), in-band insertion loss is less than 0.5 dB, return loss is greater than 17.5 dB, and circuit size is only 0.24 λ_g × 0.02 λ_g (λ_g: guided wavelength at the center frequency).

Keywords: bandpass filter; capacitor-loaded; coupled lines; wideband

Corresponding author: Hairui Liu, China Academy of Information and Communications Technology, Beijing 100095, China, E-mail: liuhairui@caict.cn

Funding source: NSAF Joint Fund

Award Identifier / Grant number: U2130102

Acknowledgment

This work was supported in part by the NSAF Joint Fund under Grant U2130102, in part by the opening project of Guangxi Key Laboratory of Wireless Wideband Communication and Signal Processing under Grant GXKL06220203, and in part by the “Siyuan Scholar” Fellowship of XJTU.

Research ethics: Not applicable.
Author contributions: The authors have accepted responsibility for the entire content of this manuscript and approved its submission.
Competing interests: The authors state no conflict of interest.
Research funding: None declared.
Data availability: The raw data can be obtained on request from the corresponding author.

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Received: 2024-02-24

Accepted: 2024-04-23

Published Online: 2024-05-14

Published in Print: 2024-12-17

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https://doi.org/10.1515/freq-2024-0055

Keywords for this article

bandpass filter; capacitor-loaded; coupled lines; wideband