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25 results on '"Rensch, D. B."'

1. An experimental study of high Tc superconducting microstrip transmission lines at 35 GHz and the effect of film morphology

Author

Chorey, C. M, Bhasin, K. B, Warner, J. D, Josefowicz, J. Y, and Rensch, D. B

Subjects
Electronics And Electrical Engineering
Abstract

Microstrip transmission lines in the form of ring resonators were fabricated from a number of in-situ grown laser ablated films and post-annealed co-sputtered YBa2Cu3O(7-x) films. The properties of these resonators were measured at 35 GHz and the observed performance is examined in light of the critical temperature (Tc) and film thickness, and also the film morphology, which is different for the two deposition techniques. It is found that Tc is a major indicator of the film performance for each growth type, with film thickness becoming important as it decreases towards 1000 A. It is also found that the films with a mixed grain orientation (both a-axis and c-axis oriented grains) have poorer microwave properties as compared with the primarily c-axis oriented material. This is probably due to the significant number of grain boundaries between the different crystallites, which may act as superconducting weak links and contribute to the surface resistance.

Published
1991
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2. An experimental study of high Tc superconducting microstrip transmission lines at 35 GHz and the effect of film morphology

Author

Chorey, C. M, Bhasin, K. B, Warner, J. D, Josefowicz, J. Y, Rensch, D. B, and Nieh, C. W

Subjects
Communications And Radar
Abstract

Microstrip transmission lines in the form of ring resonators were fabricated from a number of in-situ grown laser ablated films and post-annealed co-sputtered YBa2Cu3O(7-x) films. The properties of these resonators were measured at 35 GHz and the observed performance is examined in light of the critical temperature (Tc) and film thickness and also the film morphology which is different for the two deposition techniques. It is found that Tc is a major indicator of the film performance for each growth type with film thickness becoming important as it decreases towards 100 A. It is also found that the films with a mixed grain orientation (both a axis and c axis oriented grains) have poorer microwave properties as compared with the primarily c axis oriented material. This is probably due to the significant number of grain boundaries between the different crystallites, which may act as superconducting weak links and contribute to the surface resistance.

Published
1990

9. A Solder-Free Interconnect Approach for Integrating Millimeter Wave High-Power Devices With Planar Circuitry.

Author

Choudhury, Debabani, Lawyer, Phillip H., Foschaar, James A., Wetzel, Michael D., and Rensch, D. B.

Subjects
INTEGRATED circuits, SOLDER & soldering, SEMICONDUCTORS, ELECTRONIC circuits, ELECTRIC conductivity, INFORMATION technology
Abstract

The development of commercial millimeter wave systems requires cost-effective, high-performance device/circuit assembly techniques. A solder-free thermosonic bonding approach is described here to integrate millimeter wave high-power devices with associated planar circuitry. The devices with integrated heatsink are attached to a metal block, and then ribbon bonded with planar millimeter-wave transmission line circuitry using the developed solder-free thermosonic bonding process. The assembly process is designed to minimize the stresses that damage the devices, while maintaining the bond integrity. Observations confirm that the introduction of ultrasonic energy into the bonding process significantly reduces the temperature and assembly force applied to the device. The effects of different assembly parameters on the performance of the device are also presented. [ABSTRACT FROM AUTHOR]

Published
2003
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12. High Frequency Characterization of High Temperature Superconducting Thin-Film Lines

Author

van Deventer, T. E., Katehi, P. B., Josefowicz, J. Y., and Rensch, D. B.

Abstract

An integral equation approach is applied to calculate the propagation characteristics of high temperature thin-film superconducting lines at high frequencies. To evaluate losses in these lines, the superconducting strips are replaced by frequency-dependent surface impedance boundaries. The values of these surface impedances are measured experimentally by a TE01 cavity technique. Using this method, a parametric study is performed where phase and attenuation constants as well as characteristic impedance are evaluated as functions of frequency, temperature, permittivity and geometry of the structure.

Published
1991
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13. Three-Dimensional Unstable Resonator Calculations with Laser Medium

Author

Rensch, D. B.

Abstract

A numerical procedure that uses an explicit finite difference method to solve the wave equation is described. This technique results in a propagation algorithm that can accurately propagate an arbitrary electric field through a uniform medium or a medium that is nonuniform, transversely flowing, saturable, and contains index inhomogeneities. By using the propagation algorithm to propagate an arbitrary field back and forth between two resonator mirrors, the three-dimensional transverse mode and the output beam characteristics for a laser resonator can be determined. The advantage of the finite difference method is that unlike integral techniques the computational accuracy and efficiency improve as the resonator Fresnel number increases. The computational techniques are explained, and results for several specific empty cavity confocal unstable resonators are presented and compared to results obtained using an established calculation technique. The application of the finite difference method to inhomogeneous laser media is described, and computational results for an existing CO_2 gas dynamic laser are presented and compared to measured data. The medium kinetics and shock wave models used in the calculations are described.

Published
1974

14. Comparative Studies of Extinction and Backscattering by Aerosols, Fog, and Rain at 10.6 μ and 0.63 μ

Author

Rensch, D. B. and Long, R. K.

Abstract

Theoretical calculations using continental, fog, and precipitation aerosol size distribution models are presented here for extinction and backscatter coefficients along horizontal propagation paths at sea level. The coefficients are presented for various atmospheric conditions and for wavelengths between 0.34 μ and 10.6 μ. Finally, the theoretical results are confirmed by comparison with outdoor transmission studies at 10.6 μ and 0.63 μ.

Published
1970

15. Experimental Chemical Laser Mode Control

Author

HUGHES RESEARCH LABS MALIBU CA, Rensch, D B, HUGHES RESEARCH LABS MALIBU CA, and Rensch, D B

Abstract

An experimental study was performed on integer and integer plus one- half valued equivalent Fresnel number positive branch confocal unstable resonators in a DF-CO2 flash-photolysis chemical laser. Near diffraction limited beam quality was obtained for a range of geometric output couplings from 30% to 77%. No dependence of beam quality on the resonator Fresnel number was found. This was true for uniform medium conditions as well as perturbed conditions where significant phase perturbation were introduced into the optical resonator. Extensive medium diagnostics were performed on the DF-CO2 laser and the results presented.

Published
1974

16. Chemical Laser Pulse Initiation Study.

Author

HUGHES RESEARCH LABS MALIBU CA, Parker, Jerald V., Stephens, Ronald R., Rensch, D. B., Hess, L. D., HUGHES RESEARCH LABS MALIBU CA, Parker, Jerald V., Stephens, Ronald R., Rensch, D. B., and Hess, L. D.

Abstract

The initiation of pulsed chemical laser action by a transverse electrical discharge was investigated. The laser system under study is H2-F2-HE at pressures up to 1 atmosphere. This report discusses three aspects of the electrically initiated pulsed chemical laser. These are: (1) preionization using spark generated ultraviolet radiation to provide a uniform initiating discharge, (2) parametric measurements of electrical and chemical efficiency of the electrically initiated H2-F2 laser, and (3) modeling of the pulsed H2-F2 laser system and projected performance for large-scale devices. It is the conclusion of this work that the electrically initiated H2-F2 chain reaction laser possesses an electrical efficiency significantly higher than any existing pulsed laser, and that the energy per unit volume is competitive with the best state of the art pulsed CO2 or CO lasers. (Author)

Published
1973

23. Water Vapor Continuum Absorption of Carbon Dioxide Laser Radiation near 10micro.

Author

McCoy JH, Rensch DB, and Long RK

Abstract

Laboratory measurements using a stabilized CO(2) laser and a 1-km long path absorption cell are presented here for pure water vapor and water vapor-air mixtures. An empirical extinction coefficient equation is presented and used to compute absorption for a variety of atmospheric slant paths. Finally, the laboratory results are confirmed by comparison with outdoor transmission studies over a 1.95-km path.

Published
1969
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24. Comparative Studies of Extinction and Backscattering by Aerosols, Fog, and Rain at 10.6 micro and 0.63 micro.

Author

Rensch DB and Long RK

Abstract

Theoretical calculations using continental, fog, and precipitation aerosol size distribution models are presented here for extinction and backscatter coefficients along horizontal propagation paths at sea level. The coefficients are presented for various atmospheric conditions and for wavelengths between 0.34 micro and 10.6 micro. Finally, the theoretical results are confirmed by comparison with outdoor transmission studies at 10.6 micro and 0.63 micro.

Published
1970
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25. Iterative diffraction calculations of transverse mode distributions in confocal unstable laser resonators.

Author

Rensch DB and Chester AN

Abstract

A theoretical investigation has been undertaken to study the transverse modes of two-dimensional positive branch, confocal unstable resonators. Mode amplitude and phase information is obtained from a numerical-iterative type calculation that uses the Fresnel integral for propagating the cavity radiation back and forth between resonator mirrors. Near- and far-field distributions for empty cavity resonators are presented for various resonator Fresnel numbers and magnifications, along with results of resonator mode stability and diffraction losses when cavity perturbations such as mirror misalignment and/or a uniformly saturable gain medium are included. In addition, the diffractive calculations are compared with results obtained from geometric models.

Published
1973
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