A lossy filter with resistive coupling is proposed based on substrate integrated waveguide (SIW) resonators, where nonresonating nodes are not required to simplify the realization. The sensitivity analysis of S-parameter to the resistive coupling coefficient is carried out to determine the parameters of coupling structure and mounted resistors. When resistive couplings are added to the structure, the measured 0.2-dB passband bandwidth increases from 198 to 256 MHz, compared with the case without resistive couplings. At a sacrifice on the additional insertion loss of 1.1 dB, the passband flatness and selectivity are improved significantly. The lossy SIW filter can provide a smaller in-band insertion loss than the microstrip counterparts, because the unloaded Q-factor of SIW resonators is higher than that of microstrip resonators. Moreover, a simpler topology and a less insertion loss are obtained in the proposed resistively coupled SIW filter than those of the lossy filter synthesized with lossy coupling matrix. Excellent agreement between the simulated and measured results is achieved to demonstrate our idea.
2. Williams, A. E., W. G. Bush, and R. R. Bonetti, "Predistortion techniques for multicoupled resonator," IEEE Trans. Microw. Theory Tech., Vol. 33, No. 5, 402-408, May 1985.
3. Guyette, A. C., I. C. Hunter, and R. D. Pollard, "The design of microwave bandpass filters using resonators with nonuniform Q," IEEE Trans. Microw. Theory Tech., Vol. 54, No. 11, 3914-3922, Nov. 2006.
4. Meng, M., I. C. Hunter, and J. D. Rhodes, "The design of parallel connected filter networks with nonuniform Q resonators," IEEE Trans. Microw. Theory Tech., Vol. 62, No. 1, 372-381, Jan. 2013.
5. Miraftab, V. and M. Yu, "Generalized lossy microwave filter coupling matrix synthesis and design using mixed technologies," IEEE Trans. Microw. Theory Tech., Vol. 56, No. 12, 3016-3027, Dec. 2008.
6. Miraftab, V. and M. Yu, "Advanced coupling matrix and admittance function synthesis techniques for dissipative microwave filters," IEEE Trans. Microw. Theory Tech., Vol. 57, No. 10, 2429-2438, Oct. 2009.
7. Basti, A., A. perigaud, S. Bila, S. Verdeyme, L. Estagerie, and H. Leblond, "Design of microstrip lossy filters for receivers in satellite transponders," IEEE Trans. Microw. Theory Tech., Vol. 62, No. 9, 0018-9480, Sep. 2014.
8. Chen, X.-P. and K. Wu, "Substrate integrated waveguide filters: Design techniques and structure innovations," IEEE Microw. Magazine, Vol. 15, No. 6, 121-133, Sep. 2014.
9. Wu, L.-S., X.-L. Zhou, L. Zhou, W.-Y. Yin, and J.-F. Mao, "A substrate integrated evanescent-mode waveguide filter with nonresonating node in low temperature co-fired ceramic," IEEE Trans. Microw. Theory Tech., Vol. 58, No. 10, 2654-2662, Oct. 2010.
10. Mira, F., J. Mateu, and M. Bozzi, "Substrate integrated waveguide predistorted filter at 20 GHz," IET Microw. Antennas Propag., Vol. 5, No. 8, 928-933, Jan. 2011.
11. Jedrzejewski, A., N. Leszczynska, L. Szydlowski, and M. Mrozowski, "Zero-pole approach to computer aided design of in-line SIW filters with transmission zeros," Progress In Electromagnetics Research, Vol. 131, 517-533, 2012.
12. Szydlowski, L., A. Lamecki, and M. Mrozowski, "Design of microwave lossy filter based on substrate integrated waveguide (SIW)," IEEE Microw. Wireless Compon. Lett., Vol. 21, No. 5, 249-251, May 2011.
13. Cameron, R. J., "General coupling matrix synthesis methods for Chebyshev filtering functions," IEEE Trans. Microw. Theory Techn., Vol. 47, No. 4, 433-442, Apr. 1999.