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Search Publications by: John Ladbury (Fed)

Displaying 51 - 75 of 77

Metrology Applications of Reverberation Chambers for Electromagnetic Field Probe Calibrations and Antenna Efficiency Measurements

February 13, 2005

Author(s)

Dennis Lewis, John M. Ladbury

This paper gives a brief introduction of current methods used to calibrate electric field probes as defined by IEEE Standard 1309 as well as a brief discussion of some inherent problems with the current test methods. The use of a reverberation chamber to

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

Assessing A Loaded Reverberation Chamber: Calculating Threshold Metrics

August 18, 2003

Author(s)

Christopher L. Holloway, David A. Hill, John M. Ladbury, Todd M. Lammers

In this paper we present an expression for two threshold metrics of a loaded reverberation chamber. One metric is based on the chamber quality factor (Q) and the other is based on a useable volume of a loaded reverberation chamber. These metrics are

EMC Research at NIST, Boulder

July 11, 2003

Author(s)

Perry F. Wilson, Christopher L. Holloway, Galen H. Koepke, John M. Ladbury, Arthur Ondrejka, Robert T. Johnk, Keith D. Masterson, Dennis G. Camell

N/A

Shielding Effectiveness Measurements of Materials in Nested Reverberation Chambers

May 1, 2003

Author(s)

Christopher L. Holloway, David A. Hill, John M. Ladbury, Galen H. Koepke, R. Garzia

In this paper, we present a technique for determining the shielding effectiveness of materials from nested reverberation chamber measurements. The new approach accounts for both aperture and cavity size effects. Various examples are presented to illustrate

Reverberation Chambers Measurements for the Shielding Effectiveness of Advanced Composite Materials

September 9, 2002

Author(s)

Christopher L. Holloway, R. Garzia, John M. Ladbury, David A. Hill, Galen H. Koepke

The use of advanced composite material (ACM) is drawing considerable attention in recent years as an alternative to metals. In many applications, these materials must have the ability to shield electromagnetic fields. Shielding effectiveness (SE) is the

Coupling to Devices in Electrically Large Cavities, or Why Classical EMC Evaluation Techniques are Becoming Obsolete

August 19, 2002

Author(s)

John M. Ladbury, T. H. Lehman, Galen H. Koepke

We show that the coupling between a sensor in an electrically large cavity and the outside world is a very complicated problem, with small changes inside the cavity resulting in signal changes of greater than 20 dB. However, this problem can be greatly

Pseudo-Isotropic Source for Anechoic Chamber Qualification

August 19, 2002

Author(s)

Perry F. Wilson, John M. Ladbury, Galen H. Koepke

A pseudo-isotropic source is presented. The source consists of an electrically-large cavity with internal excitation (horn antenna), a variable internal boundary condition (a rotating paddle as in a reverberation chamber), and randomly placed apertures for

Analysis of Electrically-Short Dipoles with a Nonlinear Load, Revisited

February 1, 2002

Author(s)

John M. Ladbury, Dennis G. Camell

We reexamine the characteristics of electrically short dipoles with nonlinear loads and, specifically, the early work of Motohisa Kanda. Although this problem has been examined in great detail in the past, some errors have not been addressed. We describe

Reverberation-Chamber Research - Then and Now: A review of early work and comparison with current understanding

February 1, 2002

Author(s)

Paolo Corona, John M. Ladbury, Gaetano Latmiral

The main part of this paper is an English translation (from the original Italian) of an early (1976) paper by P. Corona and G. Latmiral. Alongside this translation is an original critical review of that paper. Much of the current thory, models, and

Spatial Correlation Functions of Fields and Energy Density in a Reverberation Chamber

February 1, 2002

Author(s)

David A. Hill, John M. Ladbury

A plane-wave integral representation is used to derive spatial correlation functions for the complex electric and magnetic field components, and the results agree with previously published results derived by volume averaging of a mode sum. Results are also

Emission and Immunity Standards: Replacing Field-at-a-Distance Measurements with Total-Radiated-Power Measurements

August 1, 2001

Author(s)

Perry F. Wilson, Galen H. Koepke, John M. Ladbury, Christopher L. Holloway

The radiation and reception patterns of devices become more complicated as the measurement frequency is increased. These complicated patterns pose a challenge to EMC emission/immunity tests where the direction of maximum radiation/reception needs to be

Directivity of the Test Device in EMC Measurements 1

December 1, 2000

Author(s)

Galen H. Koepke, David A. Hill, John M. Ladbury

We present a statistical theory for estimating the directive characteristics of unintentional emitters based on the electrical size of the device. We compare this theory to directivity derived from pattern measurements in an anechoic chamber. We also use

Radiated Power Measurements in Reverberation Chambers

December 1, 2000

Author(s)

Galen H. Koepke, John M. Ladbury

The electromagnetic reverberation chamber is widely used as a test facility to generate complex fields for interference and compatibility measurements. The chamber is also effective as a method to quantify the total radiated power from an emitter

Reverberation Chamber Verification Procedures on How to Check if Your Chamber Ain't Broke and Suggestions on How to Fix It If It Is

August 1, 2000

Author(s)

John M. Ladbury

We present three tests for evaluating the agreement between measurements taken in a reverberation chamber and the expected results given by simple statistical models. We then apply these tests to a chamber that is known to be sub-optimal. We also give

Test Device Directivity for EMC Measurements

August 1, 2000

Author(s)

Galen H. Koepke, David A. Hill, John M. Ladbury

Monte Carlo Simulation of Reverberation Chamber

October 1, 1999

Author(s)

John M. Ladbury

This paper describes how to simulate a reverberation chamber using a uniform random number generator and mathematical manipulation.

Reverberation Chamber Relationships: Corrections and Improvements or Three Wrongs Can (Almost) Make a Right

August 1, 1999

Author(s)

John M. Ladbury, Galen H. Koepke

We correct a number of errors that have crept into the reverberation-chamber literature over the past several years.

Evaluation of the NASA Langley Research Center Mode-Stirred Chamber Facility

January 1, 1999

Author(s)

John M. Ladbury, Galen H. Koepke, Dennis G. Camell

We performed extensive tests on three mode-stirred (reverberation) chambers operated by the High Intensity Radiation Laboratory located at the National Aeronautics and Space Administration Langley Research (NASA/LaRC) in Hampton, VA.