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Displaying 626 - 650 of 1580

Pump-probe Faraday rotation magnetometer using two diode lasers

April 26, 2005
Author(s)
Forrest T. Charnock, Radek Lopusnik, Thomas J. Silva
A time-resolved Faraday rotation magnetometer using externally triggered pulsed diode lasers is described. This device permits measurement of the dynamic properties of polarized electronic spins in semiconductors. A non- equilibrium spin polarization is

Calibrated 200 GHz Waveform Measurement

April 1, 2005
Author(s)
Dylan Williams, Paul D. Hale, Tracy S. Clement
We develop a method for mismatch-correcting temporal waveforms measured with a high-speed electro-optic sampling system. The new calibration characterizes the source in both the time and frequency domains, and accounts for all impedances and multiple

Linearization of Large-Signal Scattering Functions

April 1, 2005
Author(s)
Jan Verspecht, Dylan Williams, Dominique Schreurs, Kate Remley, Michael McKinley
We present an improved smallsignal linearization of large-signal scatteringparameter functions that takes on a convenient form similar to scattering parameters. We develop rules for the evolution of the linearization and large-signal scattering functions

Finite-temperature modeling of nanoscale spin-transfer oscillators

March 31, 2005
Author(s)
Stephen E. Russek, Shehzaad F. Kaka, William Rippard, Matthew Pufall, Thomas J. Silva
Magnetization dynamics induced by spin-polarized currents in magnetic nanodevices have been numerically simulated using a single-domain model proposed by Slonczewski extended to include temperature effects. For currents with a spin polarization

Progress in scale-up of second-generation high-temperature superconductors at SuperPower Inc

March 9, 2005
Author(s)
Y Y. Xie, A Knoll, Y Chen, Y Li, Xiaoxiong Xiong, You-Lin Qiao, P Hou, J Reeves, T Salagaj, K Lenseth, L Civale, B Maiorov, Y Iwasa, V Solovyov, M Suenaga, Najib Cheggour, Cameron C. Clickner, John (Jack) W. Ekin, C Weber, V Selvamanickam
SuperPower is focused on scaling up second-generation (2-G) high-temperature superconductor (HTS) technology to pilot-scale manufacturing. The emphasis of this program is to develop R&D solutions for scale-up issues in pilot-scale operations to lay the

Radio Propagation Measurements During a Building Collapse: Applications for First Responders

March 3, 2005
Author(s)
Christopher L. Holloway, Galen H. Koepke, Dennis G. Camell, Catherine A. Remley, Dylan F. Williams
The National Institute of Standards and Technology is involved in a research project to improve wireless communications for first responders (firefighters and police) in large structures (i.e., large apartment and office buildings, supermarkets, sports

Measurement of Weak Signals Using a Communications Receiver System

March 1, 2005
Author(s)
Marc Rutschlin, Kate Remley, Robert T. Johnk, Dylan Williams, Galen H. Koepke
We describe the calibration of an inexpensive, reliable system for use in weak-signal detection. The calibration procedure described allows the conversion of signals measured with the communications receiver system-which is based on a standard

Optimized Arbitrary Wireless Device Arrays for Emergency Response Communications

March 1, 2005
Author(s)
William F. Young, Edward Kuester, Christopher L. Holloway
Wireless communications are essential to emergency responders. Unfortunately, a typical emergency response scenario involves communication into and within structures, which severely interfere with or completely block the radio frequency channel. In this

Second Harmonic Magneto-Resistive Imaging to Authenticate and Recover Data from Magnetic Storage Media

March 1, 2005
Author(s)
David P. Pappas, Alexey Nazarov, D Stevenson, Steven Voran, Mike E. Read, Erin M. Gormley, James Cash, Ken Marr, James Ryan
A scanning magneto-resistive (MR) microscope was developed for high resolution imaging of magnetic tapes and digital media. Second harmonic detection was used to remove thermal anomalies. We were able to image sufficient lengths of tape for authentication

Frequency modulation of spin-transfer oscillators

February 18, 2005
Author(s)
Matthew Pufall, William Rippard, Shehzaad F. Kaka, Thomas J. Silva, Stephen E. Russek
Spin-polarized dc electric current flowing into a magnetic layer can induce precession of the magnetization at a frequency that depends on current. We show that addition of an ac current to this dc bias current results in a frequency modulated (FM)

Challenges in Using a Reverberation Chamber for Probe Calibration

February 13, 2005
Author(s)
John M. Ladbury, Dennis Lewis, Galen H. Koepke, Randy Direen
We discuss some of the challenges associated with attempts to calibrate electromagnetic field probes in a reverberation chamber. These include immunity issues, problems related to the transient nature of the fields in a reverberation chamber, and

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
Displaying 626 - 650 of 1580
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