Miniaturized transmit dual-mode HTS patch filter with stripline structure

Abstract

A miniaturized dual-mode high-temperature superconducting (HTS) patch filter is described that has a stripline structure. A conventional microstrip dual-mode HTS patch filter, which has much weaker current concentration at the resonator edge, is usually used to improve the power handling capability of a filter. However, it is difficult to design a miniaturized microstrip filter because a microstrip dual-mode filter designed with a short distance between the resonators is limited in filter response by cross-coupling between nonadjacent modes. The proposed filter overcomes this problem because a stripline filter can be made smaller than a microstrip filter due to the weaker cross-coupling between resonators in the stripline filter. A four-pole dual-mode patch stripline filter with a 5.0GHz center frequency and a 100MHz bandwidth was designed using an electromagnetic simulator based on the moment method. Two Al2O3 substrates were used, each with a thickness of 0.5mm and a relative dielectric constant of 9.9. The filter was approximately 65% smaller than a microstrip filter. This indicates that a dual-mode HTS patch filter with a stripline structure can be miniaturized and have high-power handling capability.