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Displaying 626 - 650 of 1560

Measuring the Permittivity and Permeability of Lossy Materials: Solids, Liquids, Metals, and negative-Index Materials

February 1, 2005
Author(s)
James R. Baker-Jarvis, Michael D. Janezic, Billy F. Riddle, Robert T. Johnk, Christopher L. Holloway, Richard G. Geyer, Chriss A. Grosvenor
The goal of this report is to be a comprehensive guide for researchers int he area of dielectric and magnetic measurements of lossy materials. The goal is to assemble the relevant information needed to perform and interpret dielectric measurements on lossy

Errors Resulting From the Reflectivity of Calibration Targets

January 1, 2005
Author(s)
James P. Randa, Dave K. Walker, Robert L. Billinger, Amanda E. Cox
For a microwave total power radiometer, we consider the error introduced by neglecting the difference int he antenna reflection coefficient between when it views a distant scene and a nearby calibration target. An approximate expression is presented for

IPC-Split Cylinder Standard

January 1, 2005
Author(s)
James R. Baker-Jarvis
This method is intended for the nondestructive measurement of the relative permittivity and loss tangent of unclad dielectric substrates at microwave frequencies using a split-cylinder resonator

Panoramic, Ultrawideband, Diagnostic Imaging of Test Volumes

January 1, 2005
Author(s)
David R. Novotny, Robert T. Johnk, Chriss A. Grosvenor, Seturnino Canales
This paper presents developing methodologies to assess the quality and range of use (in frequency, test volume size, and test type) of EMC test facilities. Previous efforts [1-2] have focused on transmission tests that represented typical antenna and test

Representation of Acoustic Waves in Unbounded Domains

January 1, 2005
Author(s)
Bradley K. Alpert, Y Chen
Compact, time-harmonic, acoustic sources produce waves that decay too slowly to be square-integrable on a line away from the sources. We introduce an inner product, arising directly from Green s second theorem, to form a Hilbert space of these waves and

RF Behavioural Modelling Using Multisine Excitations

January 1, 2005
Author(s)
Kate Remley, Dominique Schreurs
Large-signal behavioural models for RF devices have historically been based on single- or two-tone data. This type of excitation is often not very representative, as RF devices, being used in telecommunication systems, are usually subjected to modulated

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
Displaying 626 - 650 of 1560