A method aiming to widen the upper stopband in a microwave bandpass filter based on two-conductor suspended-substrate stripline resonators is described in this letter. Applicability of the method is illustrated by simulating and fabricating fourth-order filter that has a very wide upper stopband: Δfstop/f0=7.92 measured at a level -50 dB, which is achieved because the widths of the inner resonators in the structure are 1.4 times greater than that of the outer ones.
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3. Lin, S.-C., P.-H. Deng, Y.-S. Lin, C.-H. Wang, and C. H. Chen, "Wide-stopband microstrip bandpass filters using dissimilar quarter-wavelength stepped-impedance resonators," IEEE Transactions on Microwave Theory and Techniques, Vol. 54, No. 3, 1011-1018, 2006.
doi:10.1109/TMTT.2005.864139
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doi:10.1109/LMWC.2004.832066
5. Kim, C. H. and K. Chang, "Wide-stopband bandpass filters using asymmetric stepped-impedance resonators," IEEE Microwave and Wireless Component Letters, Vol. 23, No. 2, 69-71, 2013.
doi:10.1109/LMWC.2012.2236885
6. Russian patent 2237320, published , 2004.
7. Leksikov, A. A. and F. G. Sukhin, Stripline double-wire resonator on suspended substrate, Transactions of 16th Int. Conference “Microwave & Telecommunication Technology” (CriMiCo’2006) Sevastopol, 564-565, Crimea, Ukraine, 2006.
8. Belyaev, B. A., A. M. Serzhantov, and A. A. Leksikov, "Analysis of the coupling coefficients of stripline resonators in the designs of suspended substrate filters," Journal of Communications Technology and Electronics, Vol. 55, No. 12, 1330-1339, 2010.
doi:10.1134/S1064226910120028
9. Belyaev, B. A., A. A. Leksikov, A. M. Serzhantov, and V. V. Tyurnev, "Miniature suspendedssubstrate bandpass filter," Progress In Electromagnetics Research C, Vol. 15, 219-231, 2010.
doi:10.2528/PIERC10070604
10. Zhang, Yu., K. A. Zaki, A. J. Piloto, and J. Tallo, "Miniature broadband bandpass filters using double-layer coupled stripline resonators," IEEE Transaction on Microwave Theory and Techniques, Vol. 54, No. 8, 3370-3377, 2006.
doi:10.1109/TMTT.2006.879176
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