A novel band-pass filter (BPF) with lower and upper stopband zeros is proposed. The filter mainly consists of two antisymmetric modified anti-parallel coupled-lines and double pairs of transmission lines. Compared with the traditional anti-parallel coupled-line, the new filter has a better performance at both pass band and stop band. On the basis of even-odd mode method and network theory, the filter has been analyzed in detail. In addition, a simple method to create transmission zeros is investigated, which is beneficial for controlling the stopband zeros. The proposed filter is implemented on RT/Duroid 4350 substrate. Measured results show low insertion loss of less than 1.6 dB in the pass band and good suppressing of more than 22 dB in the lower stop band. Measured results show a good agreement with simulated results.
1. Prabhu, , S. , J. S. Mandeep, and , "Microstrip bandpass filter at S band using capacitive coupled resonator," Progress In Electromagnetics Research, Vol. 76, 223-228, 2007. doi:10.2528/PIER07071205
2. Wong, , Y. S., , S. Y. Zheng, and W. S. Chan, "Multifolded bandwidth banch line coupler with filtering characteristic using coupled port feeding," Progress In Electromagnetics Research, Vol. 118, 17-35, 2011. doi:10.2528/PIER11041401
3. Ye, , C. S., Y. K. Su, M. H. Weng, C. Y. Hung, and R. Y. Yang, "Design of the compact parallel-coupled lines wideband bandpass filters using using image parameter method," Progress In Electromagnetics Research, Vol. 100, 153-173, 2010. doi:10.2528/PIER09073002
4. Cui, , D., , Y. Liu, Y. Wu, S. Li, and C. Yu, "A compact bandstop filter based on two meandered parallel-coupled lined," Progress In Electromagnetics Research, Vol. 121 , 271-279, 2011. doi:10.2528/PIER11061902
5. Chiou, , Y. C., , J. T. Kuo, and E. Cheng, "Broadband quasi-chebyshev bandpass filters with multimode stepped-impedance resonators," IEEE Trans. on Microw. Theory and Tech., 3352-3358, 2006. doi:10.1109/TMTT.2006.879131
6. Kuo, , J. T., C. Y. Fan, and S. C. Tang, "Dual-wideband bandpass filters with extended stopband based on coupled-line and coupled three-line resonators," Progress In Electromagnetics Research, Vol. 124, 1-15, 2012. doi:10.2528/PIER11120103
7. Li, , J. L. and J. X. Chen, "Microstrip bandpass filters using stepped-impedance ring resonators for harmonic suppression," Microwave and Optical Technology Letters, Vol. 44, 71-73, 2005. doi:10.1002/mop.20550
6. Wu, , Y., Y. Liu, S. Li, and C. Yu, "A new wide-stopband low-pass filter with generalized couple-line circuit and analytical theory," Progress In Electromagnetics Research,, Vol. 116, 553-567, 2011.
9. Wu, , Y., Y. Liu, S. Li, and C. Yu, "A simple microstrip bandpass filter with analytical design theory and sharp skirt selectivity," Journal of Electromagnetic Waves and Applications, Vol. 25, No. 8--9, 1253-1263, 2011. doi:10.1163/156939311795762060
10. Ma, , R., , G. Han, X. Chen, L. Li, L. Han, and W. Zhang, "Method of determining feed positions in coupled half-wavelength stepped impedance resonator bandpass filter," IET Microwaves, Antennas & Propagation, Vol. 3, 856-862, 2009. doi:10.1049/iet-map.2008.0237
11. Chiang, , C. P. and K. W. Tam, "Compact quasi-elliptic microstrip bandpass filter using terminated anti-parallel coupled-line," IET Microwaves,Antennas & Propagation , Vol. 3, 1206-1210, 2008.
12. Wu, , Y. , Y. Liu, and , "A coupled-line band-stop filter with three section transmission-line stubs and wide upper pass-band performance," Progress In Electromagnatics Research, Vol. 119, 407-421, 2011. doi:10.2528/PIER11072003
13. Lee, C.-H., C.-I. G. Hsu, and H.-K. Jhuang, "Design of a new bandpass filter using anti-parallel coupled asymmetric SIRs," IEICE Trans. Electron., Vol. E89-C, No. 4, 571-575, 2006. doi:10.1093/ietele/e89-c.4.571
14. George, I. Z., A. K. Johnson, and , "Coupled transmission line networks in an inhomogeneous dielectric medium," IEEE Trans. on Microw. Theory and Tech., Vol. 17, 753-759, 1969.
15. Hong, , J. S. and M. J. Lancaster, Microstrip Filters for RF/Microwave Applications,, Wiley, New York, 2001. doi:10.1002/0471221619