Teoría electromagnética y sistemas de radiofrecuencia y ópticos

2014/201

Numerical optimization of hybrid dielectric/HTS resonators for surface impedance evaluation of HTS films

This work describes an alternative to the traditional dielectric resonator topology used for measuring surface impedance in high temperature superconducting (HTS) films. A gap is introduced above the dielectric so that only the lower film is in direct contact with it. This arrangement has been used extensively for mechanical tuning of dielectric resonators and, when used for surface impedance measurement, it can be designed to make the losses in the upper film small relative to the overall resonator losses. Then, measured results are mostly due to one of the films and not the average of two. The specifics of a resonator design for measuring 2-inch wafers are presented. An analysis and optimization of the resonator is done using a numerically efficient mode-matching algorithm.Peer ReviewedPostprint (published version

Third-Harmonic and intermodulation distortion in bulk acoustic-wave resonators

This article discusses on the measured third-order intermodulation (IMD3) products and third harmonics (H3) appearing in a set of six different solidly mounted resonators (SMR) and bulk acoustic-wave (BAW) resonators with different shapes and stack configurations. The discussion is supported by a comprehensive nonlinear distributed circuit model that considers the nonlinear effects potentially occurring in any layer of the resonator stack. The aluminum-nitride (AlN) and silicon-dioxide (SiO2) layers are identified as the most significant contributors to the IMD3 and H3. The frequency profile of the third-order spurious signals also reveals that, in temperature-compensated resonators, where the SiO2 layers are usually thicker, the remixing effects from the second-order nonlinear terms are the major contributors to the IMD3 and H3. These second-order terms are those that explain the second-harmonic (H2) generation, whose measurements are also reported in this article. Unique values of the nonlinear material constants can explain all the measurements despite the resonators have different shapes, resonance frequencies, and stack configurations.Peer ReviewedPostprint (author's final draft

Correction to "Nonlinear Analysis of Disk Resonators: Application to Material Characterization and Filter Design

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. The application of this procedure to the determination of nonlinear material parameters from disk resonator measurements is illustrated as well as its use for simulating filters with several inter-coupled disks. Correction: J. Mateu, IEEE Trans. Appl. Superconduct., vol. 11, pp. 135–138, Mar. 2001. On p. 137 of the above paper, the first sentence of the paragraph immediately following equation (14) should read as follows.Peer Reviewe

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

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.Peer Reviewe

Correction to "Nonlinear Analysis of Disk Resonators: Application to Material Characterization and Filter Design

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. The application of this procedure to the determination of nonlinear material parameters from disk resonator measurements is illustrated as well as its use for simulating filters with several inter-coupled disks. Correction: J. Mateu, IEEE Trans. Appl. Superconduct., vol. 11, pp. 135–138, Mar. 2001. On p. 137 of the above paper, the first sentence of the paragraph immediately following equation (14) should read as follows.Peer Reviewe

Comparison between nonlinear measurements in patterned and unpatterned thin films

This work compares two alternative methods of characterizing the nonlinearities in a 10 × 10 mm2 superconducting thin film. Both methods are based on measuring the intermodulation distortion in high temperature superconducting (HTS) films. The first method measures the unpatterned film by using a rutile loaded cavity operating at the TE011 mode. The second method is based on intermodulation measurements made in a resonant coplanar line which is patterned on the same film that is used in the rutile cavity. In both experiments we use closed-form expressions and numerical techniques to extract local parameters related to the nonlinearities of the superconductor. The intermodulation data in both type of measurements can be fitted with identical nonlinear parameters of the HTS.Peer Reviewe

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

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. The application of this procedure to the determination of nonlinear material parameters from disk resonator measurements is illustrated as well as its use for simulating filters with several inter-coupled disks.Peer Reviewe

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

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. The paper also contains examples of application of HB to illustrate that this technique is useful to simulate superconductive devices other than simple test devices, and that the validity of the simulations is not restricted to low drive power levels. Most of the analyses and simulations of this paper are based on electrical parameters that describe the nonlinearities in the superconducting material. These parameters are compatible with many existing models of microwave nonlinearities in superconductors. We discuss the particulars on how to relate these electrical parameters with one of the existing models that postulates that the nonlinear effects are due to a dependence of the penetration depth on the current density in the superconductor.Peer Reviewe