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Compact input-reflectionless balanced bandpass filter with flexible bandwidth using three-line coupled structure

基于三线耦合结构的具有灵活带宽的 紧凑型平衡式输入无反射带通滤波

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Abstract

A compact input-reflectionless balanced bandpass filter (BPF) with flexible bandwidth (BW) using a three-line coupled structure (TLCS) is presented in this paper. For the differential mode (DM), the TLCS is applied to achieve the bandpass response; meanwhile, the input coupled-feed line of the TLCS is reused in the input absorption network. This design shows a good fusion of the absorptive and BPF sections, effectively reducing the circuit size, and the BWs of the two sections that can be controlled separately result in a flexibly controllable DM response BW of the proposed input-reflectionless balanced BPF. Detailed analyses of the ratio of the two-part BWs have been given for the first time, which is vital for the passband flatness and reflectionless feature. In the codesign of this work, the input-reflectionless DM bandpass response can be optimized easily, while wideband common mode (CM) noise absorption is achieved by the input absorption network. To verify the design method, a prototype with a compact layout (0.52λ×0.36λ) is designed and measured in the 0–7.0 GHz range. The DM center frequency (f0) is 2.45 GHz with a measured 3 dB fractional bandwidth of 31.4%. The simulation and measurement results with good agreement are presented, showing good performance, e.g., low insertion loss (0.43 dB), wide upper stopband for the DM bandpass response (over 20 dB rejection level up to 2.72f0), and wideband DM reflectionless and CM noise absorption (fractional absorption bandwidth of 285.7%).

摘要

本文提出一种基于三线耦合结构的具有灵活带宽的紧凑型平衡式输入无反射带通滤波器。在差模模式下, 带通响应由三线耦合结构实现, 同时三线耦合结构的输入耦合馈线被输入吸收网络复用。带通滤波部分和吸收部分实现了良好的融合, 有效地减小了电路尺寸, 并且两部分的带宽独立可控, 进而使得该滤波器的差模响应带宽具有灵活可控的特性。此外, 首次对两部分的带宽比进行详细分析,以获得通带平坦度与无反射性能的良好折衷。因此, 该协同设计的输入无反射差模带通响应具有易于优化的特点。同时, 输入端的吸收网络还实现了宽频带内的共模噪声吸收。为了验证该设计方法, 设计了一款尺寸为0.52λ×0.36λ的平衡式输入无反射滤波器, 测量范围为0–7.0 GHz。测得差模响应的中心频率为2.45 GHz, 3 dB相对带宽为31.4%。实测和仿真结果展现了良好的一致性, 并且该滤波器具有0.43 dB的低插入损耗、较宽的差模上阻带(超过20 dB的抑制水平至2.72倍频)以及宽带的差模无反射和共模噪声吸收(吸收相对带宽为285.7%)等优点。

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Correspondence to Jianxin Chen  (陈建新).

Additional information

Project supported by the National Natural Science Foundation of China (No. 20201438)

Contributors

Yahui ZHU designed the research, processed the data, and drafted the paper. Jing CAI, Wei QIN, Wenwen YANG, and Jianxin CHEN helped organize the paper. Yahui ZHU and Jianxin CHEN revised and finalized the paper.

Compliance with ethics guidelines

Yahui ZHU, Jing CAI, Wei QIN, Wenwen YANG, and Jianxin CHEN declare that they have no conflict of interest.

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The data that support the findings of this study are available from the corresponding author upon reasonable request.

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Zhu, Y., Cai, J., Qin, W. et al. Compact input-reflectionless balanced bandpass filter with flexible bandwidth using three-line coupled structure. Front Inform Technol Electron Eng 24, 314–326 (2023). https://doi.org/10.1631/FITEE.2200261

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  • DOI: https://doi.org/10.1631/FITEE.2200261

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