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Antennas in Material Media Near Boundaries: The Terminated Insulated Antenna

  • Ronold W. P. King
  • Margaret Owens
  • Tai Tsun Wu

Abstract

When the ambient medium in which a bare metal antenna is embedded is conducting, radial currents from the antenna into the medium decrease the axial current. This means that often only electrically relatively short antennas are useful with correspondingly small effective lengths. Radial currents can obviously be eliminated by enclosing the metal cylinder (radius a, conductivity σ c , internal impedance per unit length z i ) in a dielectric sheath (outer radius b, wave number k d = ω[μ0(ε d + d /ω)]1/2, σ d ~ 0, as shown in Fig. 17.1.1. This greatly changes the properties of the antenna. In particular, the wave number of the current is no longer the wave number kI = k1[1 + (i4πz i /ωμ0Ψ)]1/2 as given by (16.2.4)—which reduces simply to the wave number k1 = ω[μ0(ε1 + 1/ω)]1/2 of the ambient medium except at very low frequencies.

Keywords

Oceanic Crust Effective Length Ambient Medium Coaxial Line Radial Electric Field 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag New York, Inc. 1992

Authors and Affiliations

  • Ronold W. P. King
    • 1
  • Margaret Owens
    • 1
  • Tai Tsun Wu
    • 1
  1. 1.Gordon McKay LaboratoryHarvard UniversityCambridgeUSA

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