A compact microstrip bandpass filter (BPF) with multispurious suppression is presented. The filter consists of two coupled half-wavelength stepped impedance resonators (SIRs) and tapped input/output (I/O) lines. With tuning the impedance ratio (K) and length ratio (α) of SIRs, a very wide stopband can be easily achieved. The filter is designed at 2.4 GHz (f0) with a wide stopband to 20 GHz (8.16f0) and an average rejection level better than 25 dB. This study provides a simple and effective method to achieve a filter with very wide stopband and compact circuit size simultaneously. Good agreement between the full-wave electromagnetic (EM) simulation and measurement is compared.
2. Lee, C. H., I. C. Wang, and C. I. G. Hsu, "Dual-band balanced BPF using λ\4 stepped-impedance resonators and folded feed lines," Journal of Electromagnetic Waves and Applications, Vol. 23, 2441-2449.
3. Wang, J. P., B. Z. Wang, Y. X. Wang, and Y. X. Guo, "Dual-band microstrip stepped-impedance bandpass filter with defected ground structure," Journal of Electromagnetic Waves and Applications, Vol. 22, No. 4, 463-470, 2008.
4. Makimoto, M. and S. Yamashita, "Bandpass filters using parallel-coupled stripline stepped-impedance resonators," IEEE Trans. Microw. Theory Tech., Vol. 28, 1413-1417, 1980.
5. Zhang, J., J. Z. Gu, B. Cui, and X. W. Sun, "Compact and harmonic suppression open-loop resonator bandpass filter with tri-section SIR," Progress In Electromagnetics Research, Vol. 69, 93-100, 2007.
6. Chin, K. S. and D. J. Chen, "Novel microstrip bandpass filters using direct-coupled triangular stepped-impedance resonators for spurious suppression," Progress In Electromagnetics Research Letters, Vol. 12, 11-20, 2009.
7. Chen, Y. M., S. F. Chang, C. C. Chang, and T. J. Hung, "Design of stepped-impedance combline bandpass filters with symmetric insertion-loss response and wide stopband range," IEEE Trans. Microw. Theory Tech., Vol. 55, 2191-2199, 2007.
8. Lin, S. C., Y. S. Lin, and C. H. Chen, "Extendedstopband band-pass filter using both half- and quarter-wavelength resonators," IEEE Microw. Wireless Compon. Lett., Vol. 16, 43-45, 2006.
9. Tang, C. W. and H. H. Liang, "Parallel-coupled stacked sirs bandpass filters with open-loop resonators for suppression of spurious responses," IEEE Microw. Wireless Compon. Lett., Vol. 15, 802-804, 2005.
10. Wang, Y. X., "Microstrip cross-coupled tri-section stepped-impedance bandpass filter with wide stop-band performance," Journal of Electromagnetic Waves and Applications, Vol. 23, No. 2-3, 289-296, 2009.
11. IE3D Simulator, Zeland Software, Inc., Fremont, CA, 1997.
12. Lin, W. J., C.-S. Chang, J.-Y. Li, D.-B. Lin, L.-S. Chen, and M. P. Houng, "Improved compact broadband bandpass filter using branch stubs co-via structure with wide stopband characteristic," Progress In Electromagnetics Research C, Vol. 5, 45-55, 2008.