Ground Model Options in the NEC-4.2 Antenna Code

Technical Report · Wed Jun 15 04:00:00 EDT 2011

DOI:https://doi.org/10.2172/1117909· OSTI ID:1117909

Burke, G. J. ^[1]

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1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

The antenna modeling code NEC–4 includes a capability for modeling antennas above or in a homoeneous ground using interpolation in tables of Sommerfeld integrals and asymptotic approximations for large distances. This model has been validated in a number of ways and yields accurate results for common antennas such as monopoles on ground stakes and ground screens and horizontal wires very close to the earth. The original NEC–4 Sommerfeld interpolation was set up for typical ground parameters and has difficulties covering the range of conductivity up to seawater at lower HF. Errors are sometimes seen in plots as discontinuities or spikes, especially in the H field which is obtained from a numerical evaluation of the curl of E. A new ground option has now been added in the version NEC–4.2 with a more accurate interpolation method and asymptotic approximations and direct evaluation of H. Filling the interpolation tables takes somewhat longer than in the original method, but time to fill the matrix is about the same. Since desktop computers are now more than an order of magnitude faster than the large computers used when NEC–4 was first released in 1992, it is reasonable to trade some speed for accuracy. The original Sommerfeld/interpolation method, which is still available, uses the input option GN2 while the new method is obtained with GN3. Some initial results of the new method are compared with the old solution here.

• Research Organization: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 1117909
• Report Number(s): LLNL-TR--490316
• Country of Publication: United States
• Language: English

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97 MATHEMATICS AND COMPUTING