A Novel Compact Eight-Pole HTS Bandpass Filter Employing CPW Quarter-Wavelength Symmetric Diverging Resonators

This paper presents a novel compact high temperature superconducting bandpass filter that employs coplanar-waveguide quarter-wavelength symmetric diverging resonators. The coplanar-waveguide symmetric diverging resonator has a structure in which the open side diverges and then is folded over several times symmetrically in order to shorten the overall length of the resonator. The proposed resonator is 2.4 mm or less in length for use in the 5-GHz band, whereas the conventional straight resonator is approximately 6.4 mm long. An eight-pole Chebyshev bandpass filter is designed using the proposed symmetric diverging resonators. The entire length of the eight-pole filter is 26 mm. The frequency response of the fabricated filter agrees well with electromagnetic simulation results, and achieves a degree of miniaturization of 50% or more compared to the conventional filter in which straight resonators are arranged serially