The Electromagnetic Field of a Horizontal Electric Dipole in the Presence of a Plane Boundary

Abstract

The vertical electric dipole is an effective and very useful transmitter when erected in air on the surface of the earth or ocean and operated in the range of frequencies used in broadcast radio communication. Antenna lengths of a quarter- or half-wavelength in air are practical and directional arrays are readily constructed. The entire far field along the surface of the earth or sea is a lateral wave often called the Norton surface wave. At lower frequencies required for communication with submerged submarines, the vertical dipole becomes impractical because it cannot be made high enough to have a reasonable electrical length and radiation resistance. When embedded in the earth or sea (Region 1, wave number k₁) near a boundary with air, rock, or sediment (Region 2, wave number k₂), the effectiveness of the vertical dipole is greatly diminished because its field is multiplied by the very small factor (k ₂ /k ₁ )². This restricts its application to the near range and part of the intermediate range unless enormous amounts of power are supplied.