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Displaying 676 - 700 of 1582

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.

Errors due to the reflectivity of calibration targets

September 20, 2004
Author(s)
James P. Randa, Dave K. Walker, Amanda Cox, Robert L. Billinger
For a microwave total-power radiometer, we consider the error introduced by neglecting the difference in the antenna reflection coefficient between when it views a distant scene and when it views a nearby calibration target. An approximate expression is

Antenna Gain Factor Equivanlent for TEM Cells

September 6, 2004
Author(s)
Perry F. Wilson
This paper derives a gain factor equivalent for TEM cells. The gain factor is then used in simple transmission fomulas to investigate emissions tests in TEM cells and correlation of TEM cell emissions measuremetns to other methods. The correlation

The Effects of Loading Configurations on the Performance of Reverberation Chambers

September 6, 2004
Author(s)
Christopher L. Holloway, Todd Lammers, John M. Ladbury
The presence of lossy objects in reverberation chamber may significantly disturb the reverberant environment and affect the desired field statistics. In this paper, we present a numerical study of the effects of different loading configurations on the

Uncertainty Analysis of Radar Cross Section Calibration at Etcheron Valley Range

September 1, 2004
Author(s)
Lorant A. Muth, Dale M. Diamond, John A. Lelis
The Etcheron Valley Range, Naval Air Warfare Center, Weapons Division at China Lake, CA conducts monostatic and bistatic radar cross section measurements on various targets of interest to DoD. This document, which follows general guidelines proposed by the

Quantum-Based Microwave Power Measurements: Proof-of-Concept Experiment

August 1, 2004
Author(s)
Thomas P. Crowley, E. A. Donley, T P. Heavner
An initial proof-of-concept experiment to measure microwave power based on quantum-mechanical principles is presented. Ground state cesium atoms exposed to 9.192631770 GHz microwave oscillate between two hyperfine states at a rate that is proportional to

Quantum-Based Microwave Power Measurements: Proof-Of-Concept Experiment

August 1, 2004
Author(s)
Thomas P. Crowley, E. A. Donley, T P. Heavner
An initial proof-of-concept experiment to measure microwave power based on quantum-mechanical principles is presented. Ground state cesium atoms exposed to 9.192631770 GHz microwave oscillate between two hyperfine states at a rate that is proportional to

TEM horn antennas: A promising new technology for compliance testing

August 1, 2004
Author(s)
Chriss A. Grosvenor, Robert T. Johnk, David R. Novotny, Seturnino Canales
Abstract-This paper discusses the advantages of using a TEM-horn antenna over conventional EMC antennas such as the log-periodic, hybrids, or biconical antennas. Important issues such as frequency coverage, linearity, time-resolution of events, cost, and

Large-angle, gigahertz-rate random telegraph switching induced by spin-momentum transfer

July 27, 2004
Author(s)
Matthew Pufall, William Rippard, Shehzaad F. Kaka, Stephen E. Russek, Thomas J. Silva, Jordan A. Katine, Matt Carey
We show that a spin-polarized dc current passing through a small magnetic element induces two-state, random telegraph switching of the magnetization via the spin-momentum transfer effect. The resistances of the states differ by up to 50% of the change due

Measuring residual resistivity ratio of high-purity Nb

July 27, 2004
Author(s)
Loren F. Goodrich, Theodore C. Stauffer, Jolene Splett, Dominic F. Vecchia
We compared methods of measuring the residual resistivity ratio (RRR) of high-purity Nb using transport current. Our experimental study is intended to answer some fundamental questions about the best measurement for RRR and the biases that may exist among

Variable-temperature critical-current measurements on a Nb-Ti wire

July 27, 2004
Author(s)
Loren F. Goodrich, Theodore C. Stauffer
We made variable-temperature critical-current (I c) measurements on a commercial multifilamentary Nb-Ti wire for temperatures (T) from 4 to 9 K and magnetic fields (H) from 0 to 11.5 T using transport current. The measurements cover the whole range of

Arrays of magnetoresistive sensors for nondestructive testing

July 20, 2004
Author(s)
David P. Pappas, Fabio C. da Silva, Alexy V. Nazarov
Magnetic field distributions were measured for test stripline structures with anisotropic magnetoresistive (AMR), thin film Permalloy sensors. Linear arrays of eight barber-pole-type AMR sensors were used to increase the speed of the imaging and stability

Finite coplanar waveguide width effects in pulsed inductive microwave magnetometry

July 12, 2004
Author(s)
Michael Schneider, Anthony B. Kos, Thomas J. Silva
The effect of finite coplanar waveguide (CPW) width on the measurement of the resonance frequency in thin ferromagnetic films has been characterized for pulsed inductive microwave magnetometry. A shift in resonant frequency is a linear function of the

In-situ observation of nano-oxide formation in magnetic thin films

July 4, 2004
Author(s)
Andrew McCallum, Stephen E. Russek
In situ conductance and reflected high energy electron diffraction (RHEED) measurements were taken during the oxidation of 20-nm-thick Co and CoFe layers. The conductance shows an initial drop with exposure to oxygen followed by a period of increasing

Structure and Magnetic Switching of Thin Film HITPERM/SiO 2 Soft Magnetic Multilayers

July 4, 2004
Author(s)
Hideyuki Okumura, C Y. Um, S Y. Chu, M E. McHenry, D E. Laughlin, Anthony B. Kos
Laminated (Fe 0.7Co 0.3) 88Zr 7B 4Cu a-HITPERM/SiO 2 multilayer thin films have been previously shown to exhibit thermally activated, stepped magnetization curves associated with sequential switching of layers. A model for the thickness dependence of the

Linking Microwave Remote Sensing Measurements to Fundamental Noise Standards

July 2, 2004
Author(s)
James P. Randa, Dave K. Walker, Michael H. Francis
We outline the formalism for linking microwave remote-sensing measurements to fundamental noise standards and estimate the achievable uncertainty. Plans for the development and use of standard radiometers for this purpose are presented.
Displaying 676 - 700 of 1582
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