Analysis and modeling of linear and nonlinear microwave superconducting devices

High temperature superconducting (HTS) materials have potential applications for microwave and millimeter-wave devices. The performance of superconductors is substantially superior to normal conductors and semiconductors concerning low loss, high sensitivity and low dispersion. However, new methodologies are needed for the design and analysis of such devices. Field penetration effects must be taken into consideration, especially for high power applications. As with other fabrication technologies, it is desirable to simulate these devices before they are built to save money and time. Similarly, to exploit the exciting characteristics of these new materials, accurate and flexible models have to be developed.; An accurate analysis for microwave and millimeter-wave devices, which include high temperature superconductor materials, is presented in this dissertation. This study covers both low linear and high nonlinear power applications. This analysis is based on blending a full electromagnetic wave model with phenomenological linear and nonlinear superconductor model, and the two-fluid model. The linear model is based on the low power London's model. On the other hand, the nonlinear model is developed using the Ginzburg-Landau theory. These models are capable of fully characterizing HTS microwave devices, including obtaining the current distributions inside the superconducting material, the electromagnetic fields, and the power handling capability.; These solutions are obtained using the finite-difference scheme. The superconductor thickness is rigorously modeled. No approximations are made to the superconductor thickness. The anisotropy associated with the superconductor is also considered. The linear problem can be solved in either the frequency or the time domain. However, the nonlinear solution must be performed in the time domain. This approach is employed to investigate HTS transmission lines and filter. Results have shown that the number of superfluid electrons decreases near the edges of transmission strips as the applied power increases, indicating the breaking of superfluid electrons pairs. The linear model underestimates the magnetic field penetration inside the superconductor. The change in the losses with the applied field is much larger than the change in the velocity of the wave propagating along the device. A variation in the frequency spectrum of the applied signal resulting from the nonlinearity is seen. Also, simulation of HTS filter has revealed that dimension and layout of HTS filters must be optimized in the design cycle to avoid nonlinearity effects.; A novel nonlinear phenomenological two-fluid model for superconducting materials has also been proposed, where the thermodynamics and electromagnetics properties of HTS are considered simultaneously. This model is very useful for computer-aided design applications.