volume | PIER Journals

Abstract

This paper presents an independently tunable dual-band bandpass filter based on center shorting-stub-loaded resonators. The center shorting-stub-loaded resonator is a dual-mode resonator that generates odd-even modes approximately equal and coupled when the shorting stub is very short. Two different sizes of center shorting-stub-loaded resonators produce two separated resonant frequencies, which are mutually independent. The coupling between the source and load is introduced in the circuit by designing an appropriate coupling structure, and the skirt selectivity of the filter is greatly improved. Four varactor diodes are placed at the two open-circuit ends of the center shorting-stub-loaded resonator to control the two separated resonant frequencies. A prototype of a tunable dual-band filter with Chebyshev response is designed and fabricated. The measured results are in good agreement with the full-wave simulated results. Results show that the first passband varies in a frequency range from 0.81 GHz to 0.95 GHz with a 3 dB fractional bandwidth of 4.2% to 5%, whereas the second passband can be tuned from 1.51 GHz to 1.79 GHz with a 3 dB fractional bandwidth of 6.8% to 8%.

1. Wong, P. W. and I. C. Hunter, "Electronically reconfigurable microwave bandpass filter," IEEE Transactions on Microwave Theory and Techniques, Vol. 57, 3,070-3,079, 2009.
doi:10.1109/TMTT.2009.2033883

2. Entesari, K. and G. M. Rebeiz, "A differential 4-bit 6.5-10-GHz RF MEMS tunable filter," IEEE Transactions on Microwave Theory and Techniques, Vol. 53, 1,103-1,110, 2005.
doi:10.1109/TMTT.2005.843501

3. Entesari, K. and G. M. Rebeiz, "A 12–18-GHz three-pole RF MEMS tunable filter," IEEE Transactions on Microwave Theory and Techniques, Vol. 53, No. 8, 2,566-2,571, 2005.
doi:10.1109/TMTT.2005.852761

4. Huang, F., S. Fouladi, and R. R. Mansour, "High-tunable dielectric resonator filters using MEMS technology," IEEE Transactions on Microwave Theory and Techniques, Vol. 59, No. 12, 3,401-3,409, 2011.
doi:10.1109/TMTT.2011.2171984

5. Park, S. J., M. A. El-Tanani, I. Reines, and G. M. Rebeiz, "Low-loss 4–6-GHz tunable filter with 3-bit high-orthogonal bias RF-MEMS capacitance network," IEEE Transactions on Microwave Theory and Techniques, Vol. 56, No. 10, 2,348-2,355, 2008.
doi:10.1109/TMTT.2008.2003521

6. Nath, J., D. Ghosh, J. P. Maria, A. I. Kingon, W. Fathelbab, P. D. Franzon, and M. B. Steer, "An electronically tunable microstrip bandpass filter using thin-film Barium-Strontium-Titanate (BST) varactors," IEEE Transactions on Microwave Theory and Techniques, Vol. 53, No. 9, 2,707-2,712, 2005.
doi:10.1109/TMTT.2005.854196

7. Jiang, H., B. Lacroix, K. Choi, Y. Wang, A. T. Hunt, and J. Papapolymerou, "Ka and U band tunable bandpass filters using ferroelectric capacitors," IEEE Transactions on Microwave Theory and Techniques, Vol. 59, No. 12, 3,068-3,075, 2011.
doi:10.1109/TMTT.2011.2170088

8. Liu, B., F. Wei, and X. Shi, "Reconfigurable bandpass filter based on net-type stepped-impedance resonator," Electronics Letters, Vol. 46, No. 22, 1,506-1,507, 2010.
doi:10.1049/el.2010.2583

9. Chen, J.-X., J. Shi, Z.-H. Bao, and Q. Xue, "Tunable and switchable bandpass filters using slot-line resonators," Progress In Electromagnetics Research, Vol. 111, 25-41, 2011.
doi:10.2528/PIER10100808

10. Wang, Y.-Y., F. Wei, H. Xu, and X. W. Shi, "A tunable 1.4-2.5GHz bandpass filter based on single mode," Progress In Electromagnetics Research, Vol. 135, 261-269, 2013.
doi:10.2528/PIER12111704

11. Chaudhary, G., Y. Jeong, and J. Lim, "Dual-band bandpass filter with independently tunable center frequencies and bandwidths," IEEE Transactions on Microwave Theory and Techniques, Vol. 61, No. 1, 107-116, 2013.
doi:10.1109/TMTT.2012.2222910

12. Kim, G. R., "A novel compact tunable bandpass filter loaded varactor diode on the DGS," Journal of Information and Communication Convergence Engineering, Vol. 8, No. 3, 263-266, 2010.
doi:10.6109/jicce.2010.8.3.263

13. Feng, T., Y. Li, H. Jiang, W. Li, F. Yang, X. Dong, and H. Chen, "Tunable single-negative metamaterials based on microstrip transmission line with varactor diodes loading," Progress In Electromagnetics Research, Vol. 120, 35-50, 2011.
doi:10.2528/PIER11052203

14. Serrano, A. L. C., F. S. Correra, T.-P. Vuong, and P. Ferrari, "Synthesis methodology applied to a tunable patch filter with independent frequency and bandwidth control," IEEE Transactions on Microwave Theory and Techniques, Vol. 60, No. 3, 484-493, 2007.
doi:10.1109/TMTT.2011.2181533

15. Liu, B., F. Wei, and Q.-Y. Wu, "A tunable bandpass filter with constant absolute bandwidth," Journal of Electromagnetic Waves and Applications, Vol. 25, No. 11–12, 1596-1604, 2011.
doi:10.1163/156939311797164819

16. Huang, X.-G., L. Zhu, Q.-Y. Feng, Q.-Y. Xiang, and D.-H. Jia, "Tunable bandpass filter with independently controllable dual passbands," IEEE Transactions on Microwave Theory and Techniques, Vol. 61, No. 9, 3,200-3,208, 2013.
doi:10.1109/TMTT.2013.2273894

17. Chaudhary, G., Y. Jeong, and Lim, "Harmonic suppressed dual-band bandpass filters with tunable passbands," IEEE Transactions on Microwave Theory and Techniques, Vol. 60, No. 7, 2,115-2,123, 2012.
doi:10.1109/TMTT.2012.2197020

18. Liang, F., X.-F. Zhai, W.-Z. Lu, Q.-X. Wan, and Y.-Y. Zhang, "An independently tunable dual-band filter using asymmetric λ/4 resonator pairs with shared via-hole ground," Progress In Electromagnetics Research, Vol. 146, 99-108, 2014.
doi:10.2528/PIER14032505

Dr. Fei Liang

Dr. Weiwei Cai

Dr. Wenzhong Lu

Dr. Li Deng

Dr. Xiaofei Zhai