This paper presents a novel design of dual-band filters with individually controllable passband responses and orders. Besides the center frequency and bandwidth, the response and order of each passband can be different and controlled individually. The dual-band filter is formed by synthesizing each filter element (resonator, inverter) one by one, exploiting the corresponding individual single-band filters design tables/formulas for different prototype responses and orders. Trisection stepped-impedance resonators (TSSIR) are adopted with novel considerations as dual-band resonators, whose additional design parameters could help to realize the required in-band responses (resonances, slope parameters) and improve simultaneously the out-of-band performances (transmission zeros of TSSIR). Furthermore, they can be used to design a dual-band filter with far separation between two passbands. Meanwhile, stepped-impedance inverters are chosen as dual-band inverters with novel additional conditions to obtain symmetric passbands, which can also provide different inverter immittance parameters J/K at two center frequencies when the response or order of each passband is different. To illustrate the two passbands being controlled individually, two dual-band filters with different orders and responses are demonstrated.
2. Matthaei, G. L., L. Young, and E. M. T. Jones, Microwave Filters, Impedance Matching Networks and Coupling Structures, Ch. 8, Artech House, Norwood, MA, 1980.
3. Hong, J. S. and M. J. Lancaster, Microstrip Filter for RF/Microwave Application, Wiley, New York, 2001.
doi:10.1002/0471221619
4. Collin, R. E., Foundations for Microwave Engineering, 2nd Ed., IEEE Press, 2001.
doi:10.1109/9780470544662
5. Lai, M.-I. and S.-K. Jeng, "Compact microstrip dual-band bandpass filters design using genetic-algorithm techniques," IEEE Trans. Microwave Theory Tech., Vol. 54, 160-168, 2006.
doi:10.1109/TMTT.2005.860327
6. Shang, X., Y. Wang, G. L. Nicholson, and M. J. Lancaster, "Design of multiple-passband filters using coupling matrix optimisation," IET Microw. Antennas Propag., Vol. 6, 24-30, 2011.
doi:10.1049/iet-map.2011.0261
7. Tsai, L.-C. and C.-W. Hsue, "Dual-band bandpass filters using equal-length coupled-serial-shunted lines and Z-transform technique," IEEE Trans. Microwave Theory Tech., Vol. 53, 3265-3271, Apr. 2004.
8. Liu, Y. and W. Dou, "A dual-band filter realized by alternately connecting the main transmission- line with shunt stubs and shunt serial resonators," IEEE Microw. Wireless Compon. Lett., Vol. 19, 296-298, 2009.
doi:10.1109/LMWC.2009.2020027
9. Liu, A.-S., T.-Y. Huang, and R.-B. Wu, "A dual wideband filter design using frequency mapping and stepped-impedance resonators," IEEE Trans. Microwave Theory Tech., Vol. 56, 2921-2929, Dec. 2008.
doi:10.1109/TMTT.2008.2007357
Submit
