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Present capabilities and new developments in antenna modeling with the numerical electromagnetics code NEC

Description: Computer modeling of antennas, since its start in the late 1960's, has become a powerful and widely used tool for antenna design. Computer codes have been developed based on the Method-of-Moments, Geometrical Theory of Diffraction, or integration of Maxwell's equations. Of such tools, the Numerical Electromagnetics Code-Method of Moments (NEC) has become one of the most widely used codes for modeling resonant sized antennas. There are several reasons for this including the systematic updating a… more
Date: April 8, 1988
Creator: Burke, G. J.
Partner: UNT Libraries Government Documents Department
open access

Extending NEC to model wire objects in infinite chiral media. [Numerical electromagnetic code (NEC)]

Description: The development of a moment-method model for wire objects in an infinite chiral medium is described. In this work, the Numerical Electromagnetics Code (NEC) was extended by including a new integral-equation kernel obtained from the dyadic Green's function for an infinite chiral medium. The NEC moment-method treatment using point matching and a three-term sinusoidal current expansion was adapted to the case of a chiral medium. Examples of current distributions and radiation patterns for simple a… more
Date: January 1, 1992
Creator: Burke, G.J. (Lawrence Livermore National Lab., CA (United States)); Miller, E.K. (Los Alamos National Lab., NM (United States)) & Bhattachryya, A.K. (New Mexico State Univ., Las Cruces, NM (United States). Physical Science Lab.)
Partner: UNT Libraries Government Documents Department
open access

Low-frequency computational electromagnetics for antenna analysis

Description: An overview of low-frequency, computational methods for modeling the electromagnetic characteristics of antennas is presented here. The article presents a brief analytical background, and summarizes the essential ingredients of the method of moments, for numerically solving low-frequency antenna problems. Some extensions to the basic models of perfectly conducting objects in free space are also summarized, followed by a consideration of some of the same computational issues that affect model ac… more
Date: January 1, 1991
Creator: Miller, E.K. (Los Alamos National Lab., NM (USA)) & Burke, G.J. (Lawrence Livermore National Lab., CA (USA))
Partner: UNT Libraries Government Documents Department
open access

Wavenumbers for currents on infinite- and finite-length wires in a chiral medium

Description: There is increasing interest in determining the electromagnetic properties of material media differing from free space and the effects thereof on the radiation, propagation, and scattering of electromagnetic fields. A material property of special present interest is that of chirality. Chirality manifests itself as a handedness'' wherein a chiral medium does not support propagation of a linearly-polarized plane wave, but which instead decomposes into two circularly-polarized waves that propagate… more
Date: January 1, 1992
Creator: Bhattacharyya, A.K. (New Mexico State Univ., Las Cruces, NM (United States)); Burke, G.J. (Lawrence Livermore National Lab., CA (United States)) & Miller, E.K. (Los Alamos National Lab., NM (United States))
Partner: UNT Libraries Government Documents Department
open access

Wavenumbers for currents on infinite- and finite-length wires in a chiral medium

Description: There is increasing interest in determining the electromagnetic properties of material media differing from free space and the effects thereof on the radiation, propagation, and scattering of electromagnetic fields. A material property of special present interest is that of chirality. Chirality manifests itself as a ``handedness`` wherein a chiral medium does not support propagation of a linearly-polarized plane wave, but which instead decomposes into two circularly-polarized waves that propaga… more
Date: March 1, 1992
Creator: Bhattacharyya, A. K.; Burke, G. J. & Miller, E. K.
Partner: UNT Libraries Government Documents Department
open access

The Numerical Electromagnetics Code (NEC) - A Brief History

Description: The Numerical Electromagnetics Code, NEC as it is commonly known, continues to be one of the more widely used antenna modeling codes in existence. With several versions in use that reflect different levels of capability and availability, there are now 450 copies of NEC4 and 250 copies of NEC3 that have been distributed by Lawrence Livermore National Laboratory to a limited class of qualified recipients, and several hundred copies of NEC2 that had a recorded distribution by LLNL. These numbers d… more
Date: January 20, 2004
Creator: Burke, G J; Miller, E K & Poggio, A J
Partner: UNT Libraries Government Documents Department
open access

Extension of a thin-wire algorithm for wires moved laterally within a mesh

Description: It was shown that the accuracy of results for wires moved laterally from mesh edges can be greatly improved by taking account of the behavior of the field in the vicinity of the wire. Also, the distance to the end of the wire can be adjusted within a cell by using a general second-order difference form for the derivative. Making the wire location completely independent of the mesh would require the additional ability to tilt the wire with respect to the edges. This seems to be a considerably mo… more
Date: November 1, 1998
Creator: Burke, G J & Steich, D J
Partner: UNT Libraries Government Documents Department
open access

Extending NEC to model wire objects in infinite chiral media

Description: The development of a moment-method model for wire objects in an infinite chiral medium is described. In this work, the Numerical Electromagnetics Code (NEC) was extended by including a new integral-equation kernel obtained from the dyadic Green`s function for an infinite chiral medium. The NEC moment-method treatment using point matching and a three-term sinusoidal current expansion was adapted to the case of a chiral medium. Examples of current distributions and radiation patterns for simple a… more
Date: March 1, 1992
Creator: Burke, G. J.; Miller, E. K. & Bhattachryya, A. K.
Partner: UNT Libraries Government Documents Department
open access

A physical optics model for scattering of HF radiation by irregular terrain

Description: Physical optics models were developed for scattering of HF radiation by irregular terrain when an antenna is located on or near the scattering surface. The primary interest was in skywave radiation patterns for communication links using the ionosphere. Second-order reflections were included in the solution through an image approximation, and the UTD result for an impedance half-plane was used to reduce reflections due to truncating the current distribution on the surface. Arbitrary 2-D or 3-D t… more
Date: January 1, 1994
Creator: Burke, G. J.
Partner: UNT Libraries Government Documents Department
open access

Optimization of Aperiodic Waveguide Mode Converters

Description: Previous studies by Haq, Webb and others have demonstrated the design of aperiodic waveguide structures to act as filters and mode converters. These aperiodic structures have been shown to yield high efficiency mode conversion or filtering in lengths considerably shorter than structures using gradual transitions and periodic perturbations. The design method developed by Haq and others has used mode-matching models for the irregular, stepped waveguides coupled with computer optimization to achie… more
Date: December 9, 2004
Creator: Burke, G. J.; White, D. A. & Thompson, C. A.
Partner: UNT Libraries Government Documents Department
open access

Numerical Modeling of Left-Handed Metamaterials

Description: The EIGER method of moments program with periodic Green's function was used to model a periodic array of strips and split-ring resonators. Left-handed propagation due to negative index of refraction is demonstrated in a frequency band. The effective material parameters versus frequency are extracted from the EIGER solution.
Date: November 6, 2001
Creator: Burke, G J; Champagne, N J & Sharpe, R M
Partner: UNT Libraries Government Documents Department
open access

Comparison of equations for the EDTD solution in anisotropic and dispersive media

Description: The recursive-convolution solution for anisotropic and dispersive media was seen to yield accurate results for reflection from ferrite slabs up to a frequency limit set by the sampling interval. Depending on the application, the results shown might be considered usable up to about 300 GHz, which corresponds to about 13 cells per wavelength. Results at still higher frequencies might be usable when a time delay or frequency shift due to dispersion can be tolerated. Several different forms of the … more
Date: January 1, 1997
Creator: Burke, G. J. & Steich, D. J.
Partner: UNT Libraries Government Documents Department
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