Ronold W. P. King

The electromagnetic field of a vertical electric dipole over the Earth or sea

The analysis of King (1990) of the electromagnetic field of a vertical electric dipole over an imperfectly conducting half-space is applied to obtain the far field when the dipole is at a specified height d. The contributions by the space wave with its 1/r dependence and the lateral surface wave with its 1/r/sup 2/ dependence are separated and studied in detail when the dipole is over a wide range of media such as sea water, wet and dry Earth, lake water and dry sand. Graphs of the far-field patterns are shown. >

The electromagnetic field of a horizontal electric dipole in the presence of a three‐layered region

The electromagnetic field generated by a horizontal electric dipole in the air over the surface of a two‐layered region is determined for continuous‐wave excitation. The region of interest consists of a conductor coated with an electrically thin layer of dielectric under a half‐space of air. Simple explicit formulas are derived for the field at all points in all three regions, including the surface wave. Typical applications are to microstrip circuits and antennas and to remote sensing from the arctic ice.

Nerves in a human body exposed to low-frequency electromagnetic fields

Following a summarizing introduction in which the background research is reviewed and referenced, a detailed description is given of the properties of the elongated cell that constitutes a nerve axon. The functioning of the cell membrane is reviewed with reference to the transmission of a frequency-modulated signal. The need for successive regeneration by means of action potentials is described. Propagation within both myelinated and unmyelinated membranes is discussed. Currents and electric fields induced in the organs of the human body by external electric and magnetic fields are introduced and their determination reviewed. The interaction between these currents and electric fields and those involved in the propagation of a signal along a nerve axon is analyzed. It is shown that incident 60-Hz electric fields near high-voltage transmission lines do not induce large enough currents and fields in a nerve axon in the leg to disrupt a propagating signal. Scaling with respect to frequency and size is discussed. Surface sensations due to exposure to electric fields in the 5-15-kV/m range are analyzed. It is concluded that exposure to the electromagnetic field of a 60-Hz high-voltage transmission line or a 10-30-kHz high-power transmitting antenna should have no observable effect on the normal functioning of nerves.

A simple formula of current in dipole antennas

A simple and quantitatively accurate representation of the current distribution in a dipole antenna is derived. Numerical data are given and are found to be in good agreement with the experiment when h \geq O.15\lambda .

Driving Point and Input Admittance of Linear Antennas

An infinity in the input admittance of linear antennas owing to the use of an idealized delta‐function generator is investigated. It is shown that the infinity may be interpreted in terms of an infinite capacitance between the two halves of the antenna. The conclusion is reached that conventionally used iterative procedures are not invalidated by difficulties with respect to the driving point.

Comment on ‘‘Focus wave modes in homogeneous Maxwell’s equations: Transverse electric mode’’

The recent formulation by Brittingham [J. Appl. Phys. 54, 1179 (1983)] of a solitary electromagnetic wave called a ‘‘focus wave mode’’ in terms of three regions with discontinuities is found not to satisfy Maxwell’s equations across the discontinuities.

Compact conical antennas for wide-band coverage

A broadband antenna with a vertically polarized, omnidirectional electric field is studied. The design of the antenna and its feeding system in the wide frequency range from 20 to 1000 MHz is described and the driving-point impedance determined. Also calculated are the voltage standing-wave ratio (VSWR) and the input impedance of a transmission line connected to the antenna. More efficient operation at low frequencies is obtained by adding a length of transmission line to form a resonant section with the antenna. The effect of the different properties of the earths surface on the field pattern is treated in a companion paper. >

New formulas for the electromagnetic field of a vertical electric dipole in a dielectric or conducting half‐space near its horizontal interface

New formulas are derived for the electromagnetic field of a vertical electric dipole in a conducting or dielectric half‐space. These continuously approximate in accuracy the general complex integrals over the entire practical range, yet are quite simple. They supplement similar formulas for the horizontal electric dipole with which they are compared, and provide the means for studying the interference patterns between the direct and lateral components of the waves and the reflection and transmission of lateral waves at boundaries.

The cylindrical antenna with arbitrary driving point

A new, reasonably accurate approximate solution is obtained in trigonometric form of the distribution of current and the admittance of a cylindrical antenna when driven off center. The symmetrical problem (sleeve dipole) with two equal generators at the same distances from the center is solved first, then the antisymmetrical case with equal and opposite generators. A suitable superposition of the two results provides the solution for the dipole antenna when driven at an arbitrary point along its length. The results are sufficiently simple to be useful in the study of antennas with active or passive elements located along their length.

The complete electromagnetic field of a three‐phase transmission line over the earth and its interaction with the human body

The electromagnetic field at all points near a high‐voltage transmission line is determined in analytical form. Account is taken of the presence of the earth below the three‐wire, three‐phase power line. The electric and magnetic fields, the total axial current, and the current and power densities in the interior of a human body are determined when the body is standing on the ground under or near the line, is in an elevated basket under the line, or is reclining in bed near the height of the line. The fields are very weak and the current and power densities so small that thermal effects are ignorable, but not necessarily possible effects on nerve action, the functioning of cells, or on certain secretions.