GB318619A - Improvements in or relating to directional antenna - Google Patents

Abstract

318,619. Marconi's Wireless Telegraph Co., Ltd., (Assignees of Lindenblad, N. E.). Sept. 7, 1928, [Convention date]. Directive signalling. - A series of linear antennµ which are long relatively to the working wave-length, are collaterally spaced and are so tuned and energized as to be the seat of stationary waves. Fig. 3 illustrates the directional lobes 34, 36 and 30, 32 produced by a pair 14, 16 of such antennae, energized from a source 20 in phase opposition through tuned circuits 22, an impedance 26 being interposed, as shown, to separate the standing-wave systems on the aerials from the feed lines 24. By stagger. ing transversely the open ends of the aerial couple 14, 16 to an angle a equal to the angle made by the principal lobes with the longitudinal axis, the lobes 34, 36 are practically merged into the lobes 30, 32 as shown in Fig. 4. The spacing D between the aerial is such that D cosec. a is equal to an odd number of half wavelengths. In order to secure a unilateral lobe 30, Fig. 5, the primary couple 14, 16 is backed by an auxiliary couple 114, 116 spaced apart from the first by a distance d such that d cosec. alpha equals an odd member of quarter wavelengths. The aerials 114, 116 may be energized directly from the source 20 in phase quadrature, or they may be energized by reflection from the primary aerials 14, 16, and be tuned by a trombone slide so as to favour the production of standing waves. In the latter case the spacing is adjusted empirically. The conductors 114, 116 may be artificially lengthened by the insertion of looped sections. Fig. 8 shows two tiers of aerials 50, 52 forming a system A for horizontal transmission, the directivity of which is sharpened in azimuth by a similar system B arranged in broadside. Fig. 10 shows a modified aerial arranged to give a vertically-polarized radiation. The conductors 70, 72, 74 point in the direction of desired transmission in azimuth, whilst the angle of stagger a (between the open ends of the antennae pairs) determines the angle of elevation of the beam. The angle a remains constant over a considerable range of tuning.