Temperature Dependence of Microwave Properties of HTS Multipole Lowpass Filters Consisting of Microstrip Open‐Stub Lines

• Published in: ETRI journal 1997-07, Vol.19 (2), p.48-58, Article 48
• Main Authors: Kim, Jeha, Han, Seok Kil, Kang, Kwang‐Yong, Ahn, Dal
• Format: Article
• Language: English
• Subjects: Applied sciences; Circuit properties; Electric, optical and optoelectronic circuits; Electronics; Exact sciences and technology; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits
• ISSN: 1225-6463; 2233-7326
• DOI: 10.4218/etrij.97.0197.0022

Using high quality high‐Tc superconducting (HTS) YBCO thin films, we designed and fabricated 3‐pole, 5‐pole, and 7‐pole lowpass filters consisting of microstrip transmission lines and open‐stub lines. We measured the microwave response of the filters in the temperature range of T=85 K to 27 K. At T = 30 K, the observed inband insertion loss was 0.14 dB and 0.02 dB for the 5‐pole and 7‐pole filters, respectively. The cut‐off frequency was 4.7 GHz for the 5‐pole filter and 7.9 GHz for the 7‐pole filter. To the authors’ knowledge, the measured inband insertion losses are the best values reported so far for the open‐stub line type HTS multipole lowpass filters. The skirt property of the 5‐pole filter showed a large improvement over that of the 3‐pole filter as predicted from the simulation. We found that, to obtain a stable performance, the HTS multipole lowpass filters should be operated at the temperatures between 60% and 70% of Tc.