Progress In Electromagnetics Research C
ISSN: 1937-8718
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By J.-M. Yan, L. Cao, and H.-Y. Zhou

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A microstrip filtering balun with a wide stopband is presented. Its filtering function is realized by four meandering stepped impedance resonators (SIRs). Except for an identical fundamental-mode resonant frequency, the SIRs have different high-order resonant frequencies. Thus, the parasitic passbands are suppressed, and a wide stopband is achieved. The unbalance-to-balance transition is accomplished by introducing two coupling output ports at two symmetry positions of the output SIR. The voltages at symmetrical positions have equal magnitudes and opposite phases, thus, signals coupled from the symmetry positions also have equal magnitude and opposite phase, i.e., balanced output signals are achieved. A more general design approach is discussed in detail, and the proposed approach is similar to the design method of the conventional filter except that a small modification is made. Additionally, two kinds of external coupling structures, microstrip coupling lines and tapped line, are compared in terms of stopband performance. The comparison shows that better stopband performance is observed when utilizing the microstrip coupling lines as the external coupling structure. A filtering balun with central frequency of 2.4 GHz and Chebyshev frequency response is designed, fabricated and measured. The measured results give a reasonable agreement with the simulated ones, which verifies the effectiveness of the filtering balun.

J.-M. Yan, L. Cao, and H.-Y. Zhou, "Design of a Microstrip Filtering Balun with a Wide Stopband," Progress In Electromagnetics Research C, Vol. 70, 63-72, 2016.

1. Lin, S., J. Wang, G. Zhang, and J. Hong, "Design of microstrip tri-mode balun bandpass filter with high selectivity," Electron. Lett., Vol. 51, No. 13, 998-999, 2015.

2. Nam, H., T.-S. Yun, and J.-C. Lee, "A broadband microstrip Marchand balun with vertical coupling structure," Microw. Opt. Technol. Lett., Vol. 49, No. 4, 752-755, 2007.

3. Park, M.-J. and B. Lee, "Stubbed branch line balun," IEEE Microw. Wireless Compon. Lett., Vol. 17, No. 3, 169-171, 2007.

4. Li, J. L., S. W. Qu, and Q. Xue, "Miniaturised branch-line balun with bandwidth enhancement," Electron. Lett., Vol. 43, No. 17, 931-932, 2007.

5. Pu, X. Y., X. Y. Zhou, S. Y. Zheng, and Y. L. Long, "Wide band balun filter using open/shorted coupled line sections," Microw. Opt. Technol. Lett., Vol. 57, No. 5, 1099-1101, 2015.

6. Jung, E.-Y. and H.-Y. Hwang, "A balun-BPF using a dual mode ring resonator," IEEE Microw. Wireless Compon. Lett., Vol. 17, No. 9, 652-654, 2007.

7. Gao, S. S. and S. Sun, "Compact dual-mode balun bandpass filter with improved upper stopband performance," Electron. Lett., Vol. 47, No. 23, 1281-1283, 2011.

8. Kang, S. J. and H. Y. Hwang, "Ring-balun-bandpass filter with harmonic suppression," IET Microw. Antennas Propag., Vol. 4, No. 11, 1847-1854, 2010.

9. Cheong, P., T.-S. Lv, W.-W. Choi, and K.-W. Tam, "A compact microstrip square-loop dual-mode balun-bandpass filter with simultaneous spurious response suppression and differential performance improvement," IEEE Microw. Wireless Compon. Lett., Vol. 21, No. 2, 77-79, 2011.

10. Sun, S. and W. Menzel, "Novel dual-mode balun bandpass filters using single cross-slotted patch resonator," IEEE Microw. Wireless Compon. Lett., Vol. 21, No. 8, 415-417, 2011.

11. Hui, J. N., W. J. Feng, and W. Q. Che, "Balun bandpass filter based on multilayer substrate integrated waveguide power divider," Electron. Lett., Vol. 48, No. 10, 571-573, 2012.

12. Jiang, W., L. Zhou, A. M. Gao, W. Shen, W. Y. Yin, and J.-F. Mao, "Compact dual-mode dualband balun filter using double-sided parallel-strip line," Electron. Lett., Vol. 48, No. 21, 1351-1352, 2012.

13. Hao, Z.-C., W.-Q. Ding, and X.-P. Huo, "A wideband high selectivity filtering balun," Microw. Opt. Technol. Lett., Vol. 57, No. 5, 1107-1110, 2015.

14. Leong, Y. C., K. S. Ang, and C. H. Lee, "A derivation of a class of 3-port baluns from symmetrical 4-port networks," IEEE MTT-S Int. Microwave Symp. Digest, 1165-1168, 2002.

15. Wu, C.-H., C.-Y. Wang, and C. H. Chen, "Balanced-to-unbalanced bandpass filters and the antenna application," IEEE Trans. Micro. Theory Tech., Vol. 56, No. 11, 2474-2482, 2008.

16. Yang, T., M. Tamura, and T. Itoh, "Compact hybrid resonator with series and shunt resonances used in miniaturized filters and balun filters," IEEE Trans. Micro. Theory Tech., Vol. 58, No. 2, 390-402, 2010.

17. Huang, G.-S. and C. H. Chen, "Dual-band balun bandpass filter with hybrid structure," IEEE Microw. Wireless Compon. Lett., Vol. 21, No. 7, 356-358, 2011.

18. Feng, W.-J. and W. Che, "Wideband balun bandpass filter based on a differential circuit," IEEE MTT-S Int. Microwave Symp. Digest, 1-3, 2012.

19. He, Y. and L. Sun, "Dual-band balun bandpass filter using coupled lines with shunt open-ended stubs," Microw. Opt. Technol. Lett., Vol. 56, No. 10, 2358-2360, 2014.

20. Yeung, L. K. and K.-L. Wu, "A dual-band coupled-line balun filter," IEEE Trans. Micro. Theory Tech., Vol. 55, No. 11, 2406-2411, 2007.

21. Armando, F.-P., A. Lujambio, J. Martel, F. Medina, F. Mesa, and R. R. Boix, "Simple and compact balanced bandpass filters based on magnetically coupled resonators," IEEE Trans. Micro. Theory Tech., Vol. 63, No. 6, 1843-1853, 2015.

22. Wu, C.-H., C.-H. Wang, and C. H. Chen, "Balanced coupled-resonator bandpass filters using multisection resonators for common-mode suppression and stopband extension," IEEE Trans. Micro. Theory Tech., Vol. 55, No. 8, 1756-1763, 2007.

23. Wu, L.-S., Y.-X. Guo, J.-F. Mao, and W.-Y. Yin, "Design of a substrate integrated waveguide balun filter based on three-port coupled-resonator circuit model," IEEE Microw. Wireless Compon. Lett., Vol. 21, No. 5, 252-254, 2011.

24. Hong, J. S. and M. J. Lancaster, Microstrip Filter for RF/Microwave Applications, John Wiley & Sons, 2001.

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