Certain Factors Affecting the Gain of Directive Antennas*

Abstract

This paper analyzes the performance of antenna arrays as influenced by certain variables within the control of the designing engineer. It starts with an extremely simple analysis of the interfering effects produced by two sources of waves of the same amplitude. This is followed by a short discussion of a paper by Ronald Foster, which considers two antennas and also 16 antennas when arranged in linear array. Two antennas separated in space by 1/4 wave‐length and in phase by 1/4 period give sensibly more radiation in one direction than in the opposite. This, for convenience, has been called a unidirectional couplet. A number of these couplets may be arranged in linear array, thereby giving an extremely useful directive system. Diagrams are shown for such arrays as affected by the number and spacings of the individual couplets. The gains from such arrays are calculated and data are given showing fair agreement between calculation and observation. Directional diagrams for arrays or coaxial antennas indicate that somewhat less gain may be expected from this form than when the elements are spaced laterally. Combinations of these two types of arrays give marked directional properties in both their horizontal and vertical planes of reference. This principle has been used father generally in short‐wave communication. This paper also discusses effects resulting from combining two or more arrays. In one case the space between two arrays tends to emphasize spurious lobes. The directorial diagram of such a combination may be rotated within limits by changing the phasing between adjacent arrays or sections of an array. In all of the above cases the influence of the earth is ignored. A mathematical appendix gives general equations for calculating directional diagrams of linear arrays. Special cases of these equations apply to the figures included in the main port of the text. General equations are also given for calculating the gains of arrays. Similar equations permit the areas of diagrams to be calculated. An extended bibliography on antenna arrays is appended.

Design of Ultra High Aperture Efficiency Surface Wave Antenna Array Based on the Three-Dimensional Aperture Principle

“…Two rectangular holes are set so that the coaxial cables can cross the metal plate. According to the three-dimensional aperture principle and [17], the array obtains the maximum gain when element spacing (D_unit) is about 0.9λ and the maximum aperture efficiency when D_unit = 0.5λ.…”

“…Two rectangular holes are set so that the coaxial cables can cross the metal plate. According to the three-dimensional aperture principle and [17], the array obtains the maximum gain when element spacing ( _ ) D unit is about 0.9λ and the maximum aperture efficiency when _ 0.5 . D unit λ = The effect of element spacing on the performance of the array is simulated and the results shown in Figure 6 are in good agreement with the theoretical prediction.…”