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Displaying 651 - 675 of 1580

Scattering-Parameter Models and Representations for Microwave Mixers

January 1, 2005
Author(s)
Dylan F. Williams, Fabien Ndagijimana, Catherine A. Remley, Joel Dunsmore, Sean Hubert
We present straight-forward models and representations for RF and image mixers, and develop simple rules for transforming electrical problems involving mixers and signals at several frequencies into equivalent single-frequency problems. We show how those

Limits of Storage in Magnetic Materials

December 31, 2004
Author(s)
Thomas J. Silva
I summarize what is currently known about how thermal effects limit the storage capacity of magnetic disk drives. The physics of thermal fluctuations in magnetic materials is treated in some detail, though the essential points are covered in a tutorial

Superconductors: An Emerging Power Technology

December 31, 2004
Author(s)
John (Jack) W. Ekin
Superconductors offer effectively zero resistance to the flow of electricity and thus have the potential to significantly reduce Joule energy losses in the distribution and utilization of electric power, as well as the size and weight of power generators

Zigzag-shaped magnetic sensors

December 13, 2004
Author(s)
Fabio C. da Silva, Willard C. Uhlig, Anthony B. Kos, Susan A. Schima, Joe Aumentado, John Unguris, David P. Pappas
Magnetism in zigzag-shaped thin-film elements is investigated using scanning electron microscopy with polarization analysis, magnetotransport measurements, and micromagnetic simulations. We find that the angle of magnetization alternates along the length

EVM Calculation for Broadband Modulated Signals

December 1, 2004
Author(s)
Michael McKinley, Kate Remley, Maciej Myslinski, J. S. Kenney
We present a normalization that facilitates calculation of error vector magnitude (EVM) from measurements. We derive the IEEE 802.11a standard's EVM from a more basic equation. We compare EVM for various modulation types for a given power level under

Uncertainty of the NIST Electrooptic Sampling System

December 1, 2004
Author(s)
Dylan F. Williams, Paul D. Hale, Tracy S. Clement
We present an uncertainty analysis of measurements performed with NIST's electrooptic sampling system. The system measures the voltage waveform injected by a photodetector on a coplanar waveguide fabricated on an electrooptic LiTaO3 wafer. The frequency

Design for a multifrequency high magnetic field superconducting quantum interference device-detected quantitative electron paramagnetic resonance probe: Spin-lattice relaxation of cupric sulfate pentahydrate (CuSO 4 &#82265H 2 O

November 1, 2004
Author(s)
Brant Cage, Stephen E. Russek
We have designed a spectrometer for the quantitative determination of electron paramagnetic resonance (EPR) at high magnetic fields and frequencies. It uses a superconducting quantum interference device (SQUID) for measuring the magnetic moment as a

Microwave Power Imaging with Ferromagnetic Films Incorporated in Bimaterial Cantilevers

November 1, 2004
Author(s)
Thomas Mitchell (Mitch) Wallis, John M. Moreland, Billy F. Riddle, Pavel Kabos
We report an imaging technique that uses ferromagnetic films incorporated in bimaterial cantilevers for spatially resolved calorimetric detection of microwaves emitted by sources of high frequency (4 to 20 GHz) radiation. The ferromagnetic film absorbs

Simplifying and Interpreting Two-Tone Measurements

November 1, 2004
Author(s)
Kate Remley, Dylan Williams, Dominique Schreurs, John Wood
We develop a mathematical description of the response of systems to second-order memory mechanisms based on a time-varying gain modulation function. We show that intermodulation products arising from interactions at baseband have different phase symmetries

Micromechanical torque magnetometer with sub-monolayer sensitivity

October 29, 2004
Author(s)
Dong-Hoon Min, Andrew McCallum, Stephen E. Russek, John M. Moreland
We have developed a micromechanical torque sensor with sub-monolayer sensitivity for in situ monitoring of the magnetic moment of thin films during deposition. The film is deposited onto a microcantilever. The torque on the film is determined by measuring

Spin transfer switching of spin valve nanopillars using nanosecond pulsed currents

October 29, 2004
Author(s)
Shehzaad F. Kaka, Matthew Pufall, William Rippard, Thomas J. Silva, Stephen E. Russek, Jordan A. Katine, Matt Carey
Spin valve nanopillars are reversed via the mechanism of spin momentum transfer using current pulses applied perpendicular to the film plane of the device. The applied pulses were varied in amplitude from 1.8 to 7.8 mA, and varied in duration within the

Dynamic and static magnetic anisotropy in thin-film cobalt zirconium tantalum

October 26, 2004
Author(s)
John P. Nibarger, R Ewasko, Michael Schneider, Thomas J. Silva
The magnetic anisotropy values of thin amorphous cobalt zirconium tantalum (CZT) films were determined from static and dynamic measurements. Dynamic techniques show a rotatable component of anisotropy that decreases with increasing longitudinal bias field

Estimating Multiple-Reflection Uncertainties in Spherical Near-Field Measurements

October 17, 2004
Author(s)
Michael H. Francis, Jeffrey R. Guerrieri, Katherine MacReynolds, Ronald C. Wittmann
We propose a method to estimate multiple-reflection effects on test-antenna pattern and gain uncertainties in the far field derived from spherical near-field measurements. To estimate these uncertainties we make a near-field measurements on two spheres

Practical Implementation of Probe-Position Correction in Near-field Planar Scanning Measurements

October 17, 2004
Author(s)
Jeffrey R. Guerrieri, Katherine MacReynolds, Michael H. Francis, Ronald C. Wittmann, Douglas T. Tamura
Planar near-field measurements require taking amplitude and phase data on an accurate and equal space grid on the plane in front of the antenna under test. The position accuracy on this grid has been determined to be '/50. As frequencies become higher

NVNA Users Forum: Mission and Overview

October 12, 2004
Author(s)
Catherine A. Remley, Dominique Schreurs, Wendy Van Moer
This paper introduces the NVNA Users' Forum, an informal discussion group devoted to sharing information and issues related to instrumentation utilized in vector large-signal network analysis of microwave circuits and systems that contain nonlinear

Wide-Band Slot Antennas with CPW Feed Lines: Hybrid and Log-Periodic Designs

October 11, 2004
Author(s)
Alpesh Bhobe, Christopher L. Holloway, Melinda Piket-May, Richard Hall
In microwave and millimeter wave applications, slot antennas fed by coplanar waveguides (CPW) are receiving increasing attention. These antennas have several useful properties, such as wider bandwidth as compared to microstrip patch antennas and easier

Electrical material property measurements using a free-field, ultra-wideband system

October 1, 2004
Author(s)
Chriss A. Grosvenor, Robert T. Johnk, David R. Novotny, Seturnino Canales, James R. Baker-Jarvis, Michael D. Janezic, Jim L. Drewniak, Marina Kolednitseva, Jianmin Zhang, Poornachander Rawa
Abstract: Nondestructive measurements of materials using TEM horn antennas and an ultra-wideband measurement system are presented. Time-domain gating and genetic algorithms are used to process the data and extract the dielectric properties of the material

Nonlinear Modeling of Tunnel Diode Detectors

September 24, 2004
Author(s)
Dave K. Walker, Kevin Coakley, Jolene Splett
We investigate the sensitivity and nonlinear properties of a tunnel diode microwave detector as functions of the input power and the load impedance presented at the detector's output. We compare the two-tone method estimate of nonlinearity with precise

Standard Radiometers and Targets for Microwave Remote Sensing

September 24, 2004
Author(s)
James P. Randa, Amanda Cox, Dave K. Walker, Michael H. Francis, Katherine MacReynolds, Jeffrey R. Guerrieri
We describe the NIST effort to develop brightness-temperature standards for microwave and millimeter-wave frequencies. Results of preliminary measurements at 26 GHz are presented.
Displaying 651 - 675 of 1580
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