GB373692A - Improvements in or relating to antenna systems - Google Patents

Abstract

373,692. Directive wireless signalling. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Marconi House, Strand, London.-(Assignees of Carter, P. S. ; Port Jefferson, Long Island, New York, U.S.A.) March 13, 1931, No. 7813. Convention date, June 11, 1930. [Class 40 (v).] A directional antenna system comprises a pair of angularly disposed linear conductors, a plurality of half wavelengths long, and energized to produce standing waves thereon, the direction of radiation being the bisector of the angle formed by the conductors. In the arrangements shown in Figs. 2, a, b, c, a transmission line 10 supplies out of phase energy to a pair of wires A, B forming an angle 2alpha with each other and either joined together at their apex and fed intermediate their ends or forming continuations of the transmission lines or preferably joined through a U-shaped loop 12 whose length can be adjusted by the bridge 14, the feeder being tapped adjustably to the loop at 18. The loop is non-radiating and can be made of suitable length so that the system presents a pure resistive load to the transmission line, which is equal to the surge impedance of the line for maximum efficiency. The angle alpha is determined from the value of # which makes the expression for the field strength H, in the direction desired, a maximum. H is given for a conductor an odd number of half wavelengths long by the expression and for one an even number of half wavelengths long by An empirical formula which may be used is:-alpha=50À9 (1/#)<-0À513> degrees, where # is the wavelength. In order further to concentrate the beam pairs of wire A, B and A<1>, B<1>, Fig. 4, may be placed in parallel horizontal planes at least one half wavelength apart, the lower pair being at least one half wavelength above the ground. To obtain a unidirectional characteristic the system is duplicated, Fig. 5, a further set of wires a, b, being placed behind the set A, B an odd number of quarter wavelengths and having standing waves generated thereon ninety degrees leading or lagging those in A, B, according to whether forward or backward radiation is desired. Several of these systems may be placed broadside on, Fig. 8, or end on, Fig. 9, being excited in the latter case with suitable lagging or leading phase-difference between each unit U. Alternatively, the units may be arranged to form a diamond shaped figure, Fig. 10, or in overlapping formation, Fig. 10a. Specifications 340,892 and 346,023 are referred to.