Search

Mechanisms for conduction via low-frequency noise measurements of High-Tc Thin-film microbridges

REA Auditado

We have investigated possible mechanisms for conduction in high-T/sub c/ thin-film microbridges biased into the voltage state via the low-frequency noise properties. Measurements on thinned YBCO microbridges indicate that the voltage noise power spectral density S/sub V/(f) is proportional to the DC voltage. Peer reviewed

Tema: general: 

• Ingeniería y Ciencias Aplicadas›Ingeniería›Ingeniería Eléctrica

Analysis and Simulation of the Effects of Distributed Nonlinearities in Microwave Superconducting Devices

REA Auditado

This paper presents a comprehensive study of microwave nonlinearities in superconductors, with an emphasis on intermodulation distortion and third-harmonic generation. It contains the analysis of various resonant and nonresonant test devices and its validation using numerical simulations based on harmonic balance (HB). The HB simulations made on test devices show that the closed-form equations for intermodulation and third-harmonic generation are only valid at low power levels.

Tema: general: 

• Ingeniería y Ciencias Aplicadas›Ingeniería›Ingeniería Eléctrica

Modeling superconducting transmission line bends and their impact on nonlinear effects.

REA Auditado

This paper reports on a numerical technique to obtain the current distribution in the annular bent sections of planar layouts. This is used to obtain the linear and nonlinear circuit distributed parameters modeling a superconducting strip bend and its impact on intermodulation distortion. As an example, we analyze a superconductive open-loop resonator and assess the linear and nonlinear contribution of its bends in its overall linear and nonlinear performance. These simulations are very useful for optimizing the resonators of a filter in order to minimize its nonlinear distortion.

Tema: general: 

• Ingeniería y Ciencias Aplicadas›Ingeniería›Ingeniería Eléctrica

6.763 Applied Superconductivity, Fall 2001

REA Auditado

Phenomenological approach to superconductivity, with emphasis on superconducting electronics. Electrodynamics of superconductors, London's model, and flux quantization. Josephson Junctions and superconducting quantum devices, equivalent circuits, and high-speed superconducting electronics. Quantized circuits for quantum computing. Overview of type II superconductors, critical magnetic fields, pinning, the critical state model, superconducting materials, and microscopic theory of superconductivity. Alternate years.

Tema: general: 

• Ingeniería y Ciencias Aplicadas›Ciencias Computacionales

Analysis of dielectric-loaded cavities for characterization of the nonlinear properties of high temperature superconductors

REA Auditado

This work describes and compares two alternative methods of analyzing dielectric-loaded cavities for measurement of intermodulation distortion in HTS films. One of them is based on assuming a specific type of HTS nonlinearities and developing theoretical equations based on them. The second is based on a numerical approach that can be applied to many types of nonlinearities. Both methods are shown to work on measured data of representative HTS films. Peer reviewed

Tema: general: 

• Ingeniería y Ciencias Aplicadas›Ingeniería›Ingeniería Eléctrica

HTS nonlinearities in microwave disk resonators

REA Auditado

This article describes a procedure for the calculation of the intermodulation behavior of the TM010 mode in high temperature superconducting (HTS) disk resonators from a description of the local HTS nonlinearities. Successful cross-checks are performed by comparing the theoretical results with experimental measurements and simulations based on the multiport harmonic balance algorithm for a specific model of HTS nonlinearity.

Tema: general: 

• Ingeniería y Ciencias Aplicadas›Ingeniería›Ingeniería Eléctrica

Harmonic balance algorithms for the nonlinear simulation of HTS devices

REA Auditado

This paper describes the application of Harmonic Balance algorithms to predict nonlinear effects in planar High Temperature Superconductors (HTS) microwave circuits. The resulting algorithms are fast and efficient and can be used both for the characterization of the nonlinearities in the HTS material, and for the prediction of the behavior of an HTS circuit given the parameters of these nonlinearities (such as a dependence of the surface impedance on the current density).

Tema: general: 

• Ingeniería y Ciencias Aplicadas›Ingeniería›Ingeniería Eléctrica

Nonlinear Analysis of Disk Resonators. Application to Material Characteritzation and Filter Design.

REA Auditado

A procedure for the numerical prediction of the microwave nonlinear behavior (intermodulation products, degradation of quality factors, etc.) of TM010 disk resonators has been developed. The procedure is based on relating a very general description of HTS nonlinearities with the circuit elements of a nonlinear radial transmission line. This radial transmission line is then analyzed using the harmonic balance algorithm. Successful cross-checks are performed by comparing simulations with theoretical results obtained for a specific model of HTS nonlinearity.

Tema: general: 

• Ingeniería y Ciencias Aplicadas›Ingeniería›Ingeniería Eléctrica

Analysis and Simulation of Distributed Nonlinearities in Ferroelectrics and superconductors for Microwave Applications

REA Auditado

This paper gives closed-form equations for the intermodulation and third harmonic signals generated in a nonlinear transmission line with distributed quadratic nonlinearities in the conductor and dielectric. Although the formulation developed is general, it is intended to be used in planar devices combining high-temperature superconductor (HTS) and oxide ferroelectrics. The analysis in this paper shows that the intermodulation and third harmonic signals produced by an HTS tend to cancel those of a ferroelectric, and that full cancellation is theoretically possible.

Tema: general: 

• Ingeniería y Ciencias Aplicadas›Ingeniería›Ingeniería Eléctrica

Application of selective leaching in fabrication of thin film ybco devices

REA Auditado

Ethylenediamine solutions have been shown to turn bulk YBCO into insulating materials. The effect of these solutions on thin YBCO films is studied. In both unpatterned and patterned films, a smooth decrease in critical currents, a transition to normal state, and a subsequent gradual increase in resistance are observed as a function of exposure time to the solution. It is noted that these characteristics might make this process desirable for weak-link and on-film resistor fabrication. Peer reviewed

Tema: general: 

• Ingeniería y Ciencias Aplicadas›Ingeniería›Ingeniería Eléctrica