Development of High-Speed Tuning System for HTS Filters

S. Ohshima, M. Ohsaka, J. H. Lee, S. Takeuchi, H. Kinouchi, S. Ono, Y. Takano, T. Nakamura, M. Yokoo, and A. Saito

Abstract— We developed a high-speed tuning system for HTS microstrip line (MSL) filters using a dielectric tuning plate, dielectric trimming rods, and conducting trimming rods. The tuning plate has windows through which the dielectric and conducting trimming rods pass. It was designed for a 3-pole filter with 5 GHz center frequency (f_c) and 100 MHz bandwidth (BW) using a 3-dimensional electromagnetic simulator. We simulated the shift of the f_c to frequencies below 500 MHz using the tuning plate with a dielectric constant of 45 and improving the insertion loss (IL), the pass-band ripple, and the BW of the filter responses by adjusting the positions of the ceramic and copper (Cu) trimming rods. In the experiment, the positions of the plate and the rods above the filter were adjusted by using high-resolution stepping motors, which function at room temperature. The minimum step of moving the plate and the rods was 0.001 mm. We found that the f_c was shifted to 500 MHz while retaining the IL, pass-band ripple, and BW by experimental evaluation. The time taken by the 500 MHz tuning was less than 1 second. These results indicate that our method and system will be useful for the next generation of wireless communication systems.

Index Terms— high-speed tuning, HTS filter, trimming rods, tuning plate

Manuscript received August 18, 2008. The authors thank T. Takeuchi for technical supports of the refrigerator. This work was supported in part by "Research and development of fundamental technologies for advanced radio frequency spectrum sharing in mobile communication systems" from the Ministry of Internal Affairs and Communications of Japan, Science, Sports, and Culture, Grant-in-Aid for Scientific Research (C) 18560325, 2006-2008, and JST. A part of this work was carried out in the clean room of Yamagata University.
S. Ohshima is with Graduate School of Science and Engineering, Yamagata University, 4-3-16, Jonan, Yonezawa, 992-8510, Japan (corresponding author to provide phone: +81-238-26-3286; fax: +81-238-26-3293; e-mail: ohshima@yz.yamagata-u.ac.jp).
M. Ohsaka, J. H. Lee, S. Takeuchi, H. Kinouchi, S. Ono, and A. Saito are with Graduate School of Science and Engineering, Yamagata University, 4-3-16, Jonan, Yonezawa, 992-8510, Japan.
Y. Takano, T. Nakamura, and M. Yokoo are with Tohoku Seiki Industries, LTD., 3-1246, Tachiyagawa, Yamagata 990-2251, Japan.

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