On the Infinitely Long Cylindrical Antenna

Using the method of steepest descents the far field and the asymptotic form of the current distribution is obtained for an infinitely long, perfectly conducting cylindrical antenna excited by a localized electromotive force. The low frequency value of the radiation conductance is determined by integrating the radiated energy flux over a large sphere

Diffraction by a Cylindrical Obstacle

The diffraction of a plane electromagnetic wave by an infinitely long, perfectly conducting cylinder has been treated by a variational method (see the two papers by H. Levine and J. Schwinger). The incident field is assumed to be polarized in the direction of the cylinder axis, and thus the entire field is of two‐dimensional nature. This formulation yields an expression for the diffracted cylindrical wave amplitude, at distances from the cylinder large compared to its transverse dimension and the wave‐length, which is stationary relative to small independent variations of the surface currents arising from plane‐wave excitation along a pair of directions in space; furthermore, the stationary form of the diffracted amplitude is independent of the scale of the surface currents. In accordance with a theorem of Levine and Schwinger, the total plane‐wave scattering cross section is simply related to the diffracted cylindrical wave amplitude in the direction of incidence. To examine the high frequency behavior of the cross section, the surface current induced by a plane wave is taken different from zero only on the illuminated part of the cylinder, where its value is derived from the tangential component of the incident magnetic field. The resulting cross section is obtained and is shown to approach 4ɑ when kɑ approaches infinity (k=2π÷wave‐length, a equals the radius of cylinder)

On the Attenuation of Guided Waves in the Limit of High Frequencies

The conventional formulas for the attenuation of waves due to the wall losses in uniform waveguides are based on the two assumptions that the wall currents are the same as the loss-free currents and that the surface resistance of the highly conductive walls is isotropic. In the limit of high frequencies the former assumption remains valid whereas the latter assumption breaks down. As the frequency is increased the surface resistance becomes anisotropic in the sense that it assumes different values depending on whether the wall current is longitudinal or transverse. In this paper new attenuation formulas are derived, which take into account the high-frequency anisotropy of the surface resistance and hence yield accurate results for all frequencies

Radiation from Wide-Angle Conical Antennas Fed by a Coaxial Line

An approximate expression for the radiation from spherically capped conical antennas is derived by the Fourier-Laméeigen-function method. Radiation patterns have been calculated for antennas with flare angle of π/6 and various lengths

The Radiation Resistance of End-Fire and Collinear Arrays

Expressions for the radiation resistances of end-fire and collinear arrays of half-wave dipoles are obtained in terms of circular functions in a form convenient for computation. No mathematical approximations except for a Fourier representation of the field of a single half-wave dipole are used. The first integral theorem of Sonine and an integral representation of the Bessel function due to Hansen are involved in the integration of the normal component of Poynting's vector. Results computed from the new formula for the radiation resistance of an n-element parallel array in which the spacings and successive phasings of the dipole elements are 180 degrees (bilateral end-fire) agree closely with those of Pistolkors, who used Brillouin's e.m.f. method; they are a little less than the figures of Bontsch-Bruewitsch, who numerically integrated Poynting's vector. Calculations for the radiation resistance of an n-element collinear array using the new formula are compared with those of Bontsch-Bruewitsch, with which they are in satisfactory agreement. The new formula is also used to compute the radiation resistance of an n-element unilateral end-fire array (i.e., an n-element parallel array in which the spacings and successive phasings of the dipole elements are 90 degrees)

Input Impedance of Wide-Angle Conical Antennas Fed by a Coaxial Line

The input impedances for conical antennas fed by a coaxial line have been computed for several flare angles. A graph of the auxiliary functions ς_n(x)is included to facilitate impedance calculation for any large flare angle

Steady state and transient electromagnetic coupling through slabs

The problem of electromagnetic transmission through a slab where transmitting and receiving antennas are at finite distances from the slab is considered. The mathematical formulation of the problem is quite general. A detailed solution is presented for the case of a highly conducting slab exposed to sinusoidal and transient excitations. A discussion is given of the conditions under which measurements with the source and receiver at finite distances are equivalent to the same measurements with plane wave excitation

Pulsed antennas

The problem of pulsed antennas has two complementary parts: i) analysis of the radiation field when the driving voltage is given and ii) synthesis of the driven voltage when the radiation field is given. In this paper a number of heuristic procedures are presented, relating to the computation of transient radiation from elementary sources, coaxial apertures, infinitely long cylindrical antennas, finite cylindrical antennas, and loop antennas. Comparison with available rigorous solutions and experiments is also provided