In this letter, an interdigital band-pass filter is proposed for out-of-band rejection improvement. Seven quarter-wavelength resonators are employed to form the passband. Three extra transmission zeros (TZs) on both sides of the passband are implemented by introducing source-load coupling and dumbbell defected ground structures (DGS). As demonstrated by the measured results, out-of-band rejection and selectivity are improved by these three TZs, and good performances are achieved. The proposed method of increasing out-of-band rejection is feasible and applicable in the design of modern microstrip filters.
2. Jankovic, N., et al., "A compact dual-band bandpass filter using folded quarter-wavelength resonators," 2012 42nd European Microwave Conference (EuMC), IEEE, 360-363, 2012.
3. Jankovic, N., V. Radonic, and V. Crnojevic-Bengin, "Compact tri-band bandpass filter based on quarter-wavelength resonators," Journal of Electromagnetic Waves and Applications, Vol. 27, No. 6, 750-757, 2013.
doi:10.1080/09205071.2013.786206
4. Yang, Z., et al., "Design of a compact dual-band dual-mode microstrip filter with an adjustable transmission zero," 2012 IEEE MTT-S International Microwave Symposium Digest (MTT), IEEE, 1-3, 2012.
5. Wang, L., et al., "Dual-band bandpass filter using stub loaded resonators with multiple transmission zeros," 2010 9th International Symposium on Antennas Propagation and EM Theory (ISAPE), IEEE, 1208-1211, 2010.
6. Cameron, R. J., "Advanced coupling matrix synthesis techniques for microwave filters," IEEE Transactions on Microwave Theory and Techniques, Vol. 51, No. 1, 1-10, 2003.
doi:10.1109/TMTT.2002.806937
7. Zhou, M., X. Tang, and F. Xiao, "Compact dual band bandpass filter using novel E-type resonators with controllable bandwidths," Microwave and Wireless Components Letters, IEEE, Vol. 18, No. 12, 779-781, 2008.
doi:10.1109/LMWC.2008.2007696
8. Sun, S., L. Zhu, and H. H. Tan, "A compact wideband bandpass filter using transversal resonator and asymmetrical interdigital coupled lines," Microwave and Wireless Components Letters, IEEE, Vol. 18, No. 3, 173-175, 2008.
doi:10.1109/LMWC.2008.916780
9. Pozar, D. M., Microwave Engineering, 4th Ed., John Wiley & Sons Inc., USA, 2012.
10. Cameron, R. J., C. M. Kudsia, and R. R. Mansour, Microwave Filters for Communication Systems: Fundamentals, Design, and Applications, John Wiley & Sons Inc., USA, 2007.
11. Hong, J.-S. and M. J. Lancaster, Microstrip Filters for RF/Microwave Applications, John Wiley & Sons Inc., USA, 2001.
doi:10.1002/0471221619
12. Montejo-Garai, J. R., "Synthesis of N-even order symmetric filters with N transmission zeros by means of source-load cross coupling," Electronics Letters, Vol. 36, No. 3, 232-233, 2000.
doi:10.1049/el:20000242
13. Amari, S., "Direct synthesis of folded symmetric resonator filters with source-load coupling," IEEE Microwave & Wireless Components Letters, Vol. 11, No. 6, 264-266, 2001.
doi:10.1109/7260.928933
14. Boutejdar, A., et al., "A simple transformation of improved WLAN band pass to low pass filter using defected ground structure (DGS), defected microstrip structure (DMS) and multilayer-technique," Journal of Microwaves, Optoelectronics and Electromagnetic Applications, Vol. 12, No. 1, 111-130, 2013.
doi:10.1590/S2179-10742013000100010
15. Khan, M. T., et al., "Tuning of end-coupled line bandpass filter for 2.4GHz using defected ground structure (DGS) parameters," Business Engineering and Industrial Applications Colloquium (BEIAC), 2013 IEEE, 131-134, 2013.
doi:10.1109/BEIAC.2013.6560098
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