Use of double-layer coupling circuit and additional patch conductors to improve power handling capability of HTS transmit filter

Abstract

Abstract The use of a double-layer coupling circuit and additional patch conductors is proposed for improving the power handing capability of high-power high-temperature superconductor transmit filters with stripline (SL) structure. A double-layer coupling circuit is formed through the substrate between the edge of the resonator and the end of the feed line. This reduces the current concentration compared with that of a conventional gap-coupled circuit due to the large gap between the resonator and feed line of the double-layer coupling circuit. The additional patch conductors (placed in the upper layer of the resonator edge) improve the power handling capability by reducing the local magnetic field concentration. The current density distribution of two-pole SL dual-mode filters with a 5.0-GHz center frequency and 100-MHz bandwidth and with an Al2O3 substrate with a relative dielectric constant of 9.9 was investigated. An electromagnetic simulator based on the moment method was used to design the filters, and the maximum current densities at the edges of the resonator as a function of frequency were simulated. The results showed that the maximum current density in an SL filter with a double-layer coupling circuit and patch conductors was approximately 30% less than that of the conventional gap-coupled filter.