Parallel Antennas Research Articles

Array design for a specified pattern by matrix methods

A new method is presented for designing arrays of parallel wire antennas. The method relates a desired pattern with required feed voltages such that mutual coupling is taken into account in the design procedure. The technique uses matrix methods together with results of the "Method of Moments" to determine the self- and mutual impedances and the required excitations. The design method can be applied to circular, elliptical, and other planar arrays although attention is restricted here to linear arrays. The feed points and the array geometry must be specified.

On two arbitrarily located identical parallel antennas

The conventional problem of two arbitrarily located parallel antennas is solved by using an integral equation technique. The two simultaneous integral equations for the two antennas are first decoupled into two independent integral equations and then solved by an approximate method with currents represented by five trigonometric functions, three for the symmetric and two for the antisymmetric parts. Typical current distributions and input admittances are obtained for half-wave and full-wave antennas in nonstaggered, in <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">45\deg</tex> echelon, and in collinear arrangements. For the nonstaggered case, the results agree with experimental data. For the other two arrangements, no experimental data are yet available. However, the current distribution is also obtained by a numerical method. The two theoretical results agree favorably for all three cases. The five-term method can be extended to a general array of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</tex> -parallel elements. This is reserved for a further report.

Mutual impedance between two rectilinear and parallel antennas of unequal lengths with non-zero current at the ends

Mutual impedance between two rectilinear and parallel antennas of unequal lengths with non-zero current at the ends

The measurement of self and mutual impedances

There are two well-known methods which can be used to measure the self and mutual impedances of identical, parallel antennas, the symmetric-antisymmetric method, and the open circuit-short circuit method. In principle, these methods are quite simple and straightforward. In practice, however, major difficulties arise in both methods. In this paper, it is shown that by using a part of each method, the self and mutual impedances can be measured quite easily and to a good degree of accuracy.

Coupled leaky waveguides II: Two parallel slits in a cylinder

Theoretical expressions are derived for the effects of mutual coupling between two parallel leaky wave antennas which consists of slitted rectangular waveguides located in a cylinder. The expressions derived are presented in terms of the results for the mutual coupling of the same antennas but located in an infinite plane, with additional terms due to the curvature of the cylinder. The graphical presentation of the numerical attenuation constants for the cylindrical case are compared with those for the infinite plane.

Coupled leaky waveguides 1: Two parallel slits in a plane

Theoretical expressions are derived for the effects of mutual coupling between two parallel leaky wave antennas located in an infinite plane. The leaky wave antennas treated are slitted rectangular waveguides, the propagation constants of which are modified by the coupling. It is shown that the attenuation constants are influenced significantly but that the phase constants are changed only slightly, so that the coupling is different from that between neighboring surface wave lines. The nature of the coupling effects are illustrated by numerical calculations.

Self- and Mutual Impedances of Parallel Identical Antennas

A method is described for obtaining approximate second-order self- and mutual impedances of parallel identical antennas. Extensive groups of curves of the newly determined impedances are provided. Since they lead to the second-order King-Middleton impedances for isolated antennas at infinite separation, and these are known to be in excellent agreement with experimental measurements, they are necessarily more accurate than the first-order or zeroth-order values thus far available, which do not lead to experimentally verifiable impedances at infinite separation except for extremely thin antennas.

The Theory of N Coupled Parallel Antennas

The integral-equation theory of coupled antennas developed by King and Harrison, Tai and Bouwkamp for two- and three-coupled antennas is generalized to any number of units symmetrically arranged around a circle. The case of four antennas at the corners of a square is discussed in detail. Application to cage and corner-reflector antennas is indicated. The analysis of N parallel antennas arranged in line is carried out to determine the driving voltages required to maintain specified currents. It is shown that the inverse problem cannot be carried out in general except as a problem in simultaneous integral equations, but that the special conditions obtaining for half-wave dipoles permit an approximate analysis for the currents with given voltages. This is carried through.

CALCULATION OF THE IMPEDANCE PROPERTIES OF PARASITIC ANTENNA ARRAYS INVOLVING ELEMENTS OF FINITE RADIUS

Summary: After a brief resumé of a general theory for the current in coupled antennas, expressions are derived for the distribution of current along two parallel antennas of unequal length and radius. The input impedance to each antenna is then determined when the antennas are driven in phase, and in phase opposition, for applied voltages of equal magnitude. Conventional circuital relations for coupled systems yield the self‐impedance of each radiator, and mutual impedance, in terms of these four calculated impedances.Methods for obtaining optimum conditions in two element arrays, consisting of a driven antenna in proximity to a director or reflector are considered.

An Electromechanical Calculator for Directional-Antenna Patterns

An electromechanical calculator has been designed for the rapid solution of directional-antenna patterns. After the desired antenna parameters have been set up, the machine automatically draws the field-intensity curve to any desired scale on a sheet of polar co-ordinate paper and indicates the rms value for drawing a circle of the equivalent nondirectional pattern. The fundamental design of the calculator does not limit the number of antennas that can be used in the directional array. As the number of antennas is increased, the greater the degree of control is possible to mould the radiation pattern into the desired shape. Not only is the horizontal directional field-intensity pattern, such as used in broadcast practice, readily available, but the field-intensity contours at any elevation angle can be drawn with equal ease. The vertical radiation characteristics of the several antennas can be selected at will. This makes it possible to explore the solid contour surface of the whole hemisphere in a relatively short time and also determine the total power radiated from the directional-antenna system. The machine is also suitable for calculating the solid contour surface of the radiation pattern from a parallel horizontal antenna array.