GB592576A - Directional antenna arrays - Google Patents

Abstract

592,576. Radio direction-finding. STANDARD TELEPHONES & CABLES, Ltd. Feb. 7, 1944, No. 2274. Convention date, March 12, 1942. [Class 40 (v)] In a dipole Adcock aerial array 1, 2, 3, 4, Fig. 3, for direction-finding, a flat horizontal conductive structure, Fig. 5, incorporating an electrostatic screen 11 for shielding the horizontal leads, is provided for the purpose of reducing errors due to any horizontally-polarized component of radiation and to the high-antenna effect. The high-frequency self-inductance of the'simple screen 11 prevents it from being an equipotential surface, and thus impairs its effectiveness, but this defect is reduced by adding conductive arms R and preferably arms Ra, Fig. 5. Further, conductors S extend beyond the dipoles 1, 2 and 3, 4 and reflect radiation so as to diminish the horizontal electric field near the dipoles. Error arising from unequal coupling, to the shield 11 or earth, of the upper and lower halves of the dipoles is balanced out, Fig. 7 (not shown), by the extension S. Two crossed pairs of Adcock aerials may be provided with a common structure, Fig. 9 (not shown), analogous to that shown in Fig. 5, or a solid horizontal sheet of metal may be used. Error due to the highantenna effect, and arising from currents which flow from the dipoles through the down leads 8, 9 in parallel, but affect the indicator 10 as a result of accidental asymmetry in the coupling, is reduced by the structure R, S, Ra, Fig. 5, in virtue of a diminution of the capacity between the dipoles and earth. The high-antenna effect is further reduced by the isolation of the dipoles 1, 2 and 3, 4 from the horizontal lines 5, 6 by means of a coupling transformer which may have an earthed screen between its windings, or preferably, Fig. 10, by means of transformers and of valves connected as push-pull cathode-followers. The horizontal conductive structure may be constructed as a unit, Fig. 14, for application to a pair of crossed Adcock aerial arrays and may comprise five circles and four rods welded together as shown.