volume | PIER Journals

Abstract

In this paper, a novel differential tri-band bandpass filter with a low-loss characteristic and high selectivity is proposed. The low-loss feature is attributed to the non-coupled structure, which circumvents the additional radiation losses from coupling slots. Furthermore, the excellent isolation and significantly enhanced selectivity between passbands are achieved via the inherent transmission zeros among them. Three desirable differential operating passbands can be conveniently allocated by adjusting the impedance ratios of the tri-section stepped impedance resonators. Consequently, the proposed filter design demonstrates a straightforward and efficient design methodology. To validate the feasibility of this approach, a differential tri-band bandpass with passbands at 1.35 GHz, 4.5 GHz, and 7.6 GHz was constructed and experimentally verified. The measured minimum insertion losses were 0.15 dB, 0.5 dB, and 1.2 dB respectively, indicating high performance. Specifically, the roll-off rates of the lower and upper edges of the three passbands are as follows: for the first passband, 30 dB/GHz and 23 dB/GHz; for the second passband, 27 dB/GHz and 25 dB/GHz; and for the third passband, 24 dB/GHz and 29 dB/GHz. The achieved concordance between simulated and measured results confirms the practicality and viability of this design for advanced communication systems.

1. Song, Yi, Haiwen Liu, Linping Feng, Cheng Guo, Shaoyong Zheng, and Zhewang Ma, "High-order balanced dual-band HTS BPF with flexible frequency ratio and sharp rejection skirts," IEEE Transactions on Microwave Theory and Techniques, Vol. 70, No. 4, 2185-2195, 2022. Google Scholar

2. Song, Yi, Haiwen Liu, Linping Feng, and Hexiu Xu, "Balanced dual-band HTS BPF with controllable frequency ratio and transmission zeros using mixed cross-coupling," IEEE Transactions on Circuits and Systems II: Express Briefs, Vol. 69, No. 11, 4313-4317, 2022. Google Scholar

3. Chen, Jian-Xin, Ying Xue, Xu Shi, Ye-Xin Huang, Wei Qin, and Yong-Jie Yang, "Design of double-ridge waveguide balanced filter and filtering power divider," IEEE Transactions on Microwave Theory and Techniques, Vol. 72, No. 10, 5929-5937, 2024. Google Scholar

4. Zhang, Cheng-Yang, Xu Shi, Ya-Hui Zhu, Ying Xue, and Jian-Xin Chen, "A compact interlaced-double-ridge waveguide balanced filter with wideband CM suppression," IEEE Microwave and Wireless Technology Letters, Vol. 35, No. 2, 169-172, 2025. Google Scholar

5. Shi, Jin and Quan Xue, "Dual-band and wide-stopband single-band balanced bandpass filters with high selectivity and common-mode suppression," IEEE Transactions on Microwave Theory and Techniques, Vol. 58, No. 8, 2204-2212, 2010. Google Scholar

6. Shi, Jin and Quan Xue, "Novel balanced dual-band bandpass filter using coupled stepped-impedance resonators," IEEE Microwave and Wireless Components Letters, Vol. 20, No. 1, 19-21, 2010. Google Scholar

7. Liu, Haiwen, Zhengbiao Wang, Shuangxi Hu, He-Xiu Xu, and Baoping Ren, "Design of tri-band balanced filter with wideband common-mode suppression and upper stopband using square ring loaded resonator," IEEE Transactions on Circuits and Systems II: Express Briefs, Vol. 67, No. 10, 1760-1764, 2020. Google Scholar

8. Zhang, Shi-Xuan, Zhi-Han Chen, and Qing-Xin Chu, "Design of tri-band balanced bandpass filter with controllable frequencies and bandwidths," 2017 IEEE MTT-S International Microwave Symposium (IMS), 1823-1825, Honololu, HI, USA, 2017.

9. Wei, Feng, Y. Jay Guo, Pei-Yuan Qin, and Xiao Wei Shi, "Compact balanced dual-and tri-band bandpass filters based on stub loaded resonators," IEEE Microwave and Wireless Components Letters, Vol. 25, No. 2, 76-78, 2015. Google Scholar

10. Zhang, Shi-Xuan, Lei-Lei Qiu, and Qing-Xin Chu, "Multiband balanced filters with controllable bandwidths based on slotline coupling feed," IEEE Microwave and Wireless Components Letters, Vol. 27, No. 11, 974-976, 2017. Google Scholar

11. Yang, Yong, Zanxian Wang, Le Xu, and Yaxin Liu, "A balanced tri-band bandpass filter with high selectivity and controllable bandwidths," International Journal of RF and Microwave Computer-Aided Engineering, Vol. 29, No. 12, e21976, 2019. Google Scholar

12. Chen, Lei, Jia Yi Peng, Min Wang, Tian Tian Zhang, and Feng Wei, "Compact balanced tri-band bandpass filter based on stub loaded resonator with high selectivity," International Journal of RF and Microwave Computer-Aided Engineering, Vol. 31, No. 12, e22911, 2021. Google Scholar

13. Lin, Shixian, Mengdan Wang, Kai Xu, and Lingyan Zhang, "A low-profile dielectric resonator filter with wide stopband for high integration on PCB," Micromachines, Vol. 14, No. 9, 1803, 2023. Google Scholar

14. Zhou, Li-Heng, Jian-Xin Chen, and Quan Xue, "Design of compact coaxial-like bandpass filters using dielectric-loaded strip resonator," IEEE Transactions on Components, Packaging and Manufacturing Technology, Vol. 8, No. 3, 456-464, 2018. Google Scholar

15. Cai, Rong, Chuan Shao, and Kai Xu, "A low-profile balanced dielectric resonator filtering power divider with isolation," Micromachines, Vol. 16, No. 1, 88, 2025. Google Scholar

16. Chen, Jian-Xin, Yang Zhan, Wei Qin, Zhi-Hua Bao, and Quan Xue, "Analysis and design of balanced dielectric resonator bandpass filters," IEEE Transactions on Microwave Theory and Techniques, Vol. 64, No. 5, 1476-1483, 2016. Google Scholar

17. Roshani, Sobhan and Saeed Roshani, "A compact coupler design using meandered line compact microstrip resonant cell (MLCMRC) and bended lines," Wireless Networks, Vol. 27, No. 1, 677-684, 2021. Google Scholar

18. Mohamadpour, Golshan, Salman Karimi, and Saeed Roshani, "Design of miniaturized 90-degree hybrid coupler with wide rejection Band using neural network," Micromachines, Vol. 15, No. 5, 657, 2024. Google Scholar

19. Zhang, Junjie, Qing Liu, Haiwen Liu, Dewei Zhang, and Dongfang Zhou, "Compact balanced tri-band superconducting band-pass filter using double square ring loaded resonators," International Journal of RF and Microwave Computer-Aided Engineering, Vol. 31, No. 3, e22530, 2021. Google Scholar

20. Ren, Baoping, Xinlei Liu, Xuehui Guan, and Zhewang Ma, "High-selectivity high-temperature superconducting triband balanced bandpass filter using symmetric stub-loaded resonator," IEEE Transactions on Applied Superconductivity, Vol. 33, No. 8, 1-5, 2023. Google Scholar

21. Hong, Jia-Shen G. and Michael J. Lancaster, Microstrip Filters for RF/Microwave Applications, John Wiley & Sons, 2004.

22. Hsu, C., Ching-Her Lee, and Yi-Huan Hsieh, "Tri-band bandpass filter with sharp passband skirts designed using tri-section SIRs," IEEE Microwave and Wireless Components Letters, Vol. 18, No. 1, 19-21, 2008. Google Scholar

23. Yin, Liyuan, Zhenghui Xue, Wu Ren, Qihao Lv, Binchao Zhang, and Cheng Jin, "High-roll-off-rate ultrathin polarization-rotating frequency selective surface," IEEE Antennas and Wireless Propagation Letters, Vol. 22, No. 7, 1592-1596, 2023. Google Scholar

Dr. Chuan Shao

Dr. Yang Li

Dr. Liang Wang

Dr. Rong Cai

Dr. Kai Xu