In this paper, a compact microstrip wideband bandpass filter (BPF) based on square ring loaded resonator (SRLR) is proposed. The SRLR is formed by loading a pair of bent open-stubs outside the diagonal corners of a square ring, which generates three split degenerated modes. The first two split modes form a dominant wideband passband. By introducing another pair of loaded open-stubs, the third split mode is moved into the passband to achieve an extra bandwidth for the wideband passband. Measured results show that this proposed BPF has a 3 dB fractional bandwidth of 69%, and the insertion loss of the BPF is less than 1.0 dB.
2. Sohail, K., P.-W. Wong, and Y.-C. Lee, "Synthesis and design of four pole ultra-wide band (UWB) bandpass filter (BPF) employing multi-mode resonators (MMR)," IEEE MTT-S Int. Microw. Symp. Dig., 1-3, 2012.
3. Chen, C.-P., J. Oda, T. Anada, Z. Ma, and S. Takeda, "Theoretical design of wideband filters with attenuation poles using improved parallel-coupled three-line units," IEEE MTT-S Int. Microw. Symp. Dig., 1-3, 2012.
4. Amir, N., M. Masoud, and H. Ahmad, "A novel wideband stepped-impedance rectangular-ring resonator bandpass filter with two notched bands," IEEE MTT-S Int. Microw. Symp. Dig., 1-3, 2012.
5. Chen, D., L. Zhu, and C.-H. Cheng, "A novel wideband bandpass filter using stub-loaded ring resonator and tapped feed," Progress In Electromagnetics Research Letters, Vol. 42, 37-44, 2013.
6. Cao, H.-L., S.-J. He, H. Li, and S.-Z. Yang, "A compact wideband bandpass filter using novel CSRR loaded QMSIW resonator with high selectivity," Progress In Electromagnetics Research C , Vol. 41, 239-254, 2013.
7. Wei, F., Z.-D. Wand, F. Yang, and X.-W. Shi, "Compact UWB BPF with triple-notched bands based on stub loaded resonator," Electron. Lett., Vol. 49, No. 2, 124-126, 2013.
8. Deng, K., J.-Z. Chen, B. Wu, T. Su, and C.-H. Liang, "Miniaturized wideband bandpass filter utilizing square ring resonator and loaded open-stub," Progress In Electromagnetics Research C, Vol. 39, 179-192, 2013.
9. Sun, S. and L. Zhu, "Wideband microstrip ring resonator bandpass filters under multiple resonances," IEEE Trans. Microw. Theory Tech., Vol. 55, No. 10, 2176-2182, 2007.
10. Ahonnom, S. and P. Akkaraekthalin, "Wideband dual mode microstrip bandpass filters using a new perturbation with notch rectangular slots," Proceeding of ECTI-CON, Vol. 1, 269-272, 2008.
11. Kim, C.-H. and K. Chang, "Wideband ring resonator bandpass filter with dual stepped impedance stubs," IEEE MTT-S Int. Microw. Symp. Dig., 229-232, 2010.
12. Fan, J., D.-Z. Zhan, C.-J. Jin, and J.-R. Luo, "Wideband microstrip bandpass filter based on quadruple mode ring resonator," IEEE Microw. Wireless Compon. Lett., Vol. 22, No. 7, 348-350, 2012.
13. Ma, Z.-W., H. Sasaki, C.-P. Chen, T. Anada, and Y. Kobayashi, "Design of a wideband bandpass filter using microstrip parallel-coupled dual-mode ring resonator," Asia-Pacific Microwave Conference Proceedings, 21-24, 2010.
14. Srisathit, K., A. Worapishet, and W. Surakampontorn, "Design of tripple-mode ring resonator for wideband microstrip bandpass filters," IEEE Trans. Microw. Theory Tech., Vol. 58, No. 11, 2867-2877, 2010.
15. Deng, K., S. Yang, S.-J. Sun, B. Wu, and X.-W. Shi, "Dual-mode dual-band bandpass filter based on square loop resonator," Progress In Electromagnetics Research C, Vol. 37, 119-130, 2013.