Design and fabrication of 5 GHz band pass filter using circle-type HTS bulk resonator

Abstract

We designed and fabricated a transmit band pass filter (BPF) using circle-type high temperature superconductor (HTS) bulk resonators. A Dy–Ba–Cu–O bulk was fabricated using a modified quench and melt growth (QMG) process and cut into specimens of 8.40 and 8.44mm in diameter and 0.5mm thick for use as the HTS bulk resonators. A three-pole stripline (SL) BPF was designed based on a Chebyshev function and the frequency response and electromagnetic field of the filter were simulated using a three-dimensional electromagnetic field simulator. From the results of the simulation, the center frequency, bandwidth, insertion loss, and ripple of the designed filter were 4.97GHz, 100MHz, 0.03dB, and 0.048dB, respectively. In the experimental results on the actual fabricated filter, the filtering response was clearly observed; however, the center frequency of 5.46GHz was higher than that of the simulation. The simulated maximum surface current in the resonators of the SL filter was approximately 86% smaller than that of a conventional hairpin filter. Furthermore, the measured response of the Dy–Ba–Cu–O bulk filter at an input power of 20dBm was almost the same as that at 0dBm. These results mean that an SL filter using a Dy–Ba–Cu–O bulk resonator may be practicable as a high-power transmit BPF.