This paper presents an ultra-wideband (UWB) high temperature superconducting (HTS) bandpass filter (BPF) based on a ring resonator loaded with a pair of symmetrical cross-shaped stepped-impedance open stubs. The main advantages are that two transmission zeros are introduced to improve passband selectivity, and high mode suppression is achieved by adjusting the impedance ratio of the cross-shaped stubs and using a pair of parallel-coupled lines. The filter is designed on double-sided YBCO/MgO/YBCO HTS films with a thickness of 0.5 mm and dielectric constant of 9.8. At 77 K, the measured 3-dB bandwidth of the filter covers 1.63 GHz~6.03 GHz. Due to the use of superconducting material, the insertion loss at the center frequency of 3.83 GHz is 0.12 dB, and the rejection is greater than 36 dB in the lower stopband, and the upper stopband with 20 dB attenuation level is extended to at least 8.5 GHz.
2. Wu, X. H., Q. X. Chu, X. K. Tian, and X. O. Yang, "Quintuple-mode UWB bandpass filter with sharp roll-off and super-wide upper stopband," IEEE Microwave Wireless Components Letters, Vol. 21, No. 12, 661-663, 2011.
doi:10.1109/LMWC.2011.2170672
3. Lan, S. W., M. H. Weng, C. Y. Hung, and S. J. Chang, "Design of a compact ultra-wideband bandpass filter with an extremely broad stopband region," IEEE Microwave Wireless Components Letters, Vol. 26, No. 6, 392-394, 2016.
doi:10.1109/LMWC.2016.2558039
4. Zhu, H. and Q. X. Chu, "Ultra-wideband bandpass filter with a notch-band using stub-loaded ring resonator," IEEE Microwave Wireless Components Letters, Vol. 23, No. 7, 341-343, 2013.
doi:10.1109/LMWC.2013.2262928
5. Kim, C. H. and K. Chang, "Ultra-wideband (UWB) ring resonator bandpass filter with a notched band," IEEE Microwave Wireless Components Letters, Vol. 21, No. 4, 206-208, 2011.
doi:10.1109/LMWC.2011.2109942
6. Moradi, B., U. Martinez-Iranzo, and J. Garcia-Garcia, "Multimode ultra-wideband filters by using a grounded open ring resonator," Microwave and Optical Technology Letters, Vol. 58, No. 8, 2001-2004, 2016.
doi:10.1002/mop.29959
7. Kim, C. H. and K. Chang, "Ring resonator bandpass filter with switchable bandwidth using stepped-impedance stubs," IEEE Transactions on Microwave Theory and Techniques, Vol. 58, No. 12, 3936-3944, 2010.
8. Lu, X. L., B. Wei, Z. Xu, B. S. Cao, X. B. Guo, X. P. Zhang, R. X. Wang, and F. Song, "Superconducting ultra-wideband (UWB) bandpass filter design based on quintuple/quadruple/triple-mode resonator," IEEE Transactions on Microwave Theory and Techniques, Vol. 63, No. 4, 1281-1293, 2015.
doi:10.1109/TMTT.2015.2402152
9. Zhou, C. X., P. P. Guo, K. Zhou, and W. Wu, "Design of a compact uwb filter with high selectivity and superwide stopband," IEEE Microwave Wireless Components Letters, Vol. 27, No. 7, 636-638, 2017.
doi:10.1109/LMWC.2017.2711509
10. Honari, M. M., R. Mirzavand, H. Saghlatoon, and P. Mousavi, "Two-layered substrate integrated waveguide filter for UWB applications," IEEE Microwave Wireless Components Letters, Vol. 27, No. 7, 633-635, 2017.
doi:10.1109/LMWC.2017.2711510
Submit
