U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Search Publications

NIST Authors in Bold

Displaying 576 - 600 of 1560

Uncertainties in Spherical Near-Field Antenna Measurements

August 3, 2005
Author(s)
Michael H. Francis, Ronald C. Wittmann, Jin-Seob Kang
A general approach is presented for estimating uncertainties in far-field parameters obtained from spherical near-field antenna measurements. The error is approximately bounded in terms of the uncertainty of the probe's receiving pattern and the

Microfabricated Atomic Frequency References

August 1, 2005
Author(s)
John Kitching, Svenja A. Knappe, Li-Anne Liew, John M. Moreland, Peter D. Schwindt, V Shah, V Gerginov, Leo W. Hollberg
Using microfabrication processes, we have been able to construct physics packages for vapour cell atomic frequency references 100x smaller than previously existing versions, with a corresponding reduction in power consumption. In addition, the devices

Critical-Current Measurements on ITER Nb3Sn Strands: Effect of Temperature

July 29, 2005
Author(s)
Loren F. Goodrich, Najib Cheggour, John (Jack) W. Ekin, Theodore C. Stauffer
Transport critical-current (II c) measurements were made on commercial multifilamentary Nb 3Sn strands at temperatures (T) from 4 to 17 K and magnetic fields (H) from 0 to 14 T. Samples investigated were taken from the stage 1 pre-production strand for the

A comprehensive evaluation of an outdoor vehicular test range

July 4, 2005
Author(s)
Robert T. Johnk, David R. Novotny, Chriss A. Grosvenor, Seturnino Canales, Janalee A. Graham, Louis L. Nagy, Doug Martin, Scott Yencer, Donald Hibbard, Tyrone L. Roach
This paper summarizes a joint industry/govenment effort to eveluate a large outdoor automotive antenna test range owned by a large automotive manufacturer.

On Peculiarities of S-Parameter Measurements

June 17, 2005
Author(s)
Yves Rolain, Wendy Van Moer, Jeffrey Jargon, Donald C. DeGroot
Measured S-parameters are a key factor for many measurement/modeling applications. Experience teaches that quantities that are derived from the measurements can contain spikes, and that they tend to grow with connection imperfections. In this paper, a

Phase Noise Effects in Sampling Microwave Measurement Systems

June 17, 2005
Author(s)
Giovanni Loglio, Jeffrey Jargon, Donald C. DeGroot, Zoya Popovic
For the purpose of bounding sources of measurement uncertainty, we examine the effects of phase noise on measured wave-variables using sampling, downconvertor-based measurement systems. Utilizing an analytical description, we show that if the phase of the

A Phasor Angle Definition Suitable for Intermodulation Measurements

June 16, 2005
Author(s)
Giovanni Loglio, Jeffrey Jargon, Donald C. DeGroot
We describe a method for preserving time-invariant phase determination of non-harmonically related signals. In particular, signals lying in complex intermodulation spectra are considered. We provide simple examples to illustrate our technique, and show how

A current-density scale for characterizing nonlinearity in high-Tc superconductors

June 1, 2005
Author(s)
Kenneth Leong, James C. Booth, Susan A. Schima
In this paper, we characterize microwave nonlinearity in a high temperature superconducting (HTS) thin film sample by measurement of a geometry-independent current-density scale j o. This quanity j specifies the strenth of a material-dependent nonlinearity

Compressive Prestrain in High-Niobium-Fraction Nb 3 Sn Superconductors

June 1, 2005
Author(s)
John (Jack) W. Ekin, Najib Cheggour, Mike Abrecht, Cameron C. Clickner, Michael Field, Seungok Hong, Jeffrey Parrell, Y. Zhang
Multifilamentary Nb 3Sn superconducting strands fabricated with high niobium fractions have exceptionally high critical-current densities but are sometimes marginally stable during testing. We report a technique for determining the pre-strain in such

Effect of Conduit Material on CICC Performance Under High Cycling Loads

June 1, 2005
Author(s)
Nicolai N. Martovetsky, Pierluigi Bruzzone, Boris Stepanov, Rainer Wesche, Chen-yu Gung, J V. Minervini, M Takayasu, Loren F. Goodrich, John (Jack) W. Ekin, Arend Nijhuis
Recent International Thermonuclear Experimental Reactor (ITER) Model Coils and tests on Nb 3Sn Cable in Conduit Conductors (CICC) showed a significant and unexpected increase in the broadness of the transition to the normal state, resulting in degradation

Nanoscale Elastic-Property Mapping with Contact-Resonance-Frequency AFM

June 1, 2005
Author(s)
Donna C. Hurley, Anthony B. Kos, Paul Rice
We describe a dynamic atomic force microscopy (AFM) method to map the nanoscale elastic properties of surfaces, thin films, and nanostructures. Our approach is based on atomic force acoustic microscopy (AFAM) techniques previously used for quantitative

Unexpected Effect of Field Angle in Magnetoresistance Measurements of High-Purity Nb

June 1, 2005
Author(s)
Loren F. Goodrich, Theodore C. Stauffer, Jolene Splett, Dominic F. Vecchia
We report on unexpected field-angle dependence of the magnetoresistance measurements of commercial, high-purity Nb discovered during our study of residual resistivity ratio ( RRR) measurements. The ( RRR) value indicates the purity and the low-temperature

Variable-Temperature Critical-Current Measurements on a Nb 3 Sn Wire

June 1, 2005
Author(s)
Loren F. Goodrich, Theodore C. Stauffer
We made variable-temperature critical-current (I c) measurements on a commercial multifilamentary Nb 3Sn wire for temperatures (T) from 4 to 17 K and magnetic fields (H) from 0 to 12 T using transport current. The sample had a diameter of 0.811 mm and a Cu

Low-frequency noise measurements on commercial magnetoresistive magnetic field sensors

May 17, 2005
Author(s)
Nathan Stutzke, Stephen E. Russek, David P. Pappas, Mark Tondra
Low frequency noise was measured in the frequency range from 0.1 Hz to 10 kHz on a variety of commercially available magnetic sensors. The types of sensors investigated include anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), and tunnel

Advantages of superconducting quantum interference device-detected magnetic resonance over conventional high-frequency electron paramagnetic resonance for characterization of nanomagnetic materials

May 16, 2005
Author(s)
Brant Cage, Stephen E. Russek, David Zipse, Naresh S. Dalal
A dc-detected high-frequency electron paramagnetic resonance (HF-EPR) technique, based on a standard superconducting quantum interference device (SQUID) magnetometer, has significant advantages over traditional HF-EPR based on microwave absorption

A Behavioral Model for Reducing the Complexity of Mixer Analysis and Design

May 11, 2005
Author(s)
Alessandro Cidronali, Giovanni Loglio, Jeffrey Jargon, Gianfranco Manes
This paper considers an approach for the behavioral modeling of the conversion mechanism in a nonlinear device suitable for the analysis of RF/microwave mixers. The core of the model consists of the conversion matrix of the nonlinear cell under
Displaying 576 - 600 of 1560