Computer-aided modeling and analysis of passive microwave and millimeter-wave high-temperature superconductor circuits and components.

摘要

As their critical temperatures continue to rise, high-temperature superconductors (HTS) promise applications in microwave, and to some extent in millimeter-wave circuits, because they should exhibit lower loss, in these frequencies, than their normal metal counterparts. However, in the case of passive circuits, fundamental performance limits (finite insertion loss) still exist and apply, as explored in this thesis.; Commercial computer-aided design (CAD) and analysis software tools exist, that permit design and analysis of normal metal microwave and millimeter-wave circuits. These tools minimize design and manufacturing errors and the need for costly re-work and design iterations. In the case of HTS circuits these tools are insufficient because of three effects present in HTS circuits that do not exist in normal metal circuits. First, because of manufacturing practices, the HTS layers on substrates are usually very thin; of the order of the magnetic field penetration depth. Second, there is an additional internal inductance, the kinetic inductance, which is due to the inertia of the superelectrons. Third, high input power induces high magnetic fields and current densities which drive the superconductor into its normal state, in which it is an insulator.; This thesis is a study of these phenomena and their effects on quasi-TEM transmission line circuit performance. Methods for accounting for these effects and introducing them into currently available CAD tools are presented. These methods are applied to three example circuits for which modeled and measured performance is compared.; The viability and advantages of HTS waveguides are also studied and analyzed. A finite difference analysis program is presented.