A high-performance microstrip low-pass filter (LPF) with low cutoff frequency, negligible passband insertion loss, very sharp transition band, and deep ultra-wide stopband is designed, fabricated and measured. The presented filter is realized using three types of resonators which are coupled C-shape defected ground structure (C-CDGS), mirrored series-resonant branch loaded by radial stub, and high impedance line loaded by radial stub. A novel equivalent circuit model of the C-CDGS resonator is created, and its corresponding parameters are also extracted. The proposed filter is experimentally verified through the measured results which show good agreement with electromagnetic simulations.
2. Velidi, V. K. and S. Sanyal, "Sharp roll-off lowpass filter with wide stopband using stub-loaded coupled-line hairpin unit," IEEE Microwave and Wireless Components Letters, Vol. 21, No. 6, 301-303, May 2011.
3. Makki, S. V., et al., "Sharp response microstrip LPF using folded stepped impedance open stubs," Radioengineering, Vol. 22, No. 1, 328-332, April 2013.
4. Mousavi, S. M. H., et al., "Design of high performance LPF with excellent return loss using stepped impedance and radial resonators," International Journal of Engineering & Technology Sciences (IJETS), Vol. 03, No. 1, 32-44, January 2015.
5. Hayati, M. and A. Sheikhi, "Microstrip lowpass filter with very sharp transition band and wide stopband," ETRI Journal, Vol. 33, No. 6, 981-984, December 2011.
6. Weng, L. H., Y.-C. Guo, X.-W. Shi, and X.-Q. Chen, "An overview on defected ground structure," Progress In Electromagnetics Research B, Vol. 7, 173-189, 2008.
7. Banerji, A., "Design of a wide stopband harmonic suppressed microstrip low pass planar filter using defected ground structure," International Journal on Electrical Engineering and Informatics, Vol. 4, No. 1, 134-147, March 2012.
8. Kushwah, M. and D. Thakur, "Design of compact lowpass filter with wide stopband using I-shape," International Journal of Engineering Sciences & Research Technology, Vol. 3, No. 3, 1603-1605, March 2014.
9. Wu, J.-Y., Y.-H. Tseng, and W.-H. Tu, "Design of compact lowpass filter with ultra-wide stopband using thin slots," Progress In Electromagnetics Research C, Vol. 31, 137-151, 2012.
10. Zhang, H., Z. Xu, Y. Lin, and R. Wu, "A novel DP-EBG structure for low-pass filter of wide stopband," PIERS Proceedings, 1477-1480, Guangzhou, China, August 25-28, 2014.
11. Shaheen, M., et al., "Compact LPF design with low cutoff frequency using V-shaped DGS structure," International Journal of Electronics and Communication Engineering & Technology (IJECET), Vol. 6, No. 1, 1-7, January 2015.
12. Wang, C.-J. and T. H. Lin, "A multi-band meandered slotted-ground plane resonator and its application of lowpass filter," Progress In Electromagnetics Research, Vol. 120, 249-262, 2011.
13. Challal, M., et al., "Compact microstrip low-pass filter design with ultra-wide reject band using a novel quarter-circle DGS shape," ACES Journal, Vol. 27, No. 10, 808-815, October 2012.
14. Li, Y., H.-C. Yang, and S.-Q. Xiao, "Lowpass filter with wide stopband and sharp skirt using novel defected ground structure," Progress In Electromagnetics Research Letters, Vol. 41, 185-191, 2013.
15. Jung, S., Y.-K. Lim, and H.-Y. Lee, "A coupled-defected ground structure lowpass filter using inductive coupling for improved attenuation," Microw. and Opt. Technol. Lett., Vol. 50, No. 6, 1541-1543, June 2008.
16. Hong, J.-S. and M. J. Lancaster, "Couplings of microstrip square open-loop resonators for cross-coupled planar microwave filters," IEEE Transactions on Microwave Theory and Techniques, Vol. 44, No. 12, December 1996.
17. Belbachir Kchairi, A., et al., "A novel compact lowpass filter using open-rectangle DGS technology for microwave mixers," International Journal of Microwave and Optical Technology, Vol. 10, No. 6, November 2015.
18. Hong, J.-S. and M. J. Lancaster, Microstrip Filters for RF/Microwave Applications, John Wiley & Sons, New York, 2001.