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Search Publications by: Ronald Wittmann (Assoc)

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Displaying 76 - 100 of 158

Test-Chamber Imaging Using Spherical Near-Field Scanning

October 1, 2001
Author(s)
Ronald C. Wittmann, Michael H. Francis
Although the theory is straightforward, practical implementation of spherical near-field scanning for evaluating test chambers presents some significant challenges. Among these are the requirement for accurate probe positioning and the difficulty in

Antenna Range Imaging

October 1, 2000
Author(s)
Ronald C. Wittmann, Michael H. Francis
We present a preliminary evaluation of a microwave measurement system that has been designed to determine electromagnetic fields in the quiet-zone of an antenna measurement range and to produce an image of the sources, intended and unintended, of the

Computation of Causal Characteristic Impedances

June 12, 2000
Author(s)
Dylan F. Williams, Ronald C. Wittmann
We develop a numerical method of determining the magnitude of characteristic impedance required by causal power-normalized circuit theories from its phase using a Hilbert-transform relationship. We also estimate the uncertainty in the method.

Are the Formulas for Mode-Field Diameter Correct?

September 1, 1998
Author(s)
Ronald C. Wittmann, M. Young
We have found conceptual problems with the far-field formula 1 for mode field diameter First, the formulation is incomplete in that it ignores the obliquity factor; second, it assumes that the field at the end of a truncated fiber is identical to the mode