GB654142A - Improvements in and relating to antennae - Google Patents

Abstract

654,142. Aerials. BRITISH THOMSONHOUSTON CO., Ltd. Oct. 16, 1946, No. 30842. Convention date, Oct. 16, 1945. [Class 40 (vii)] An aerial comprises two concentric, coplanar closely spaced conductors forming two peripherally incomplete loops carrying high frequency currents in phase opposition, the electrical length of each conductor being an integral number of half-wavelengths and the conductors being spaced from a concentric conducting cylinder by a mean distance of a quarter-wavelength. In the described embodiment, which provides an aerial the radiation of which is concentrated in the horizontal plane, the loops 10, 47 are supported from the conducting cylinder 11 (which also forms a mast), by insulated supports 45, 46 the loops being relatively closely spaced with respect to each other and the loop 10 spaced from the mast 11 by a distance of 0.25# to 0.3#. High frequency energy from a source 17 is supplied to the aerial via an impedance matching arrangement comprising a stub transmission line 48, 49, one end of which is short-circuited at 49<SP>1</SP> and connected to the mast 11 and the other end of which is connected to the source 17 by means of feeder 16 and, at appropriate points close to to the latter end, to the loops 10, 47 via conductors 52, 55. A plurality of assemblies of this type may be employed to form a composite aerial for radiating greater amounts of power. The Specification as open to inspection under Sect. 91 of the Acts describes the following aerial systems. In one arrangement (Fig. 1, Cancelled), providing wide band operation with horizontal (i.e. circular) radiation the aerial comprises a single peripheral incomplete loop 10 (of length n#), co-axially supported from a conductive mast 11 by means of an insulated support 12 (of length #/4, or less), energy being supplied to the mast via transmission lines 16 and 19 and matching transformer 13. An arrangement having a similar radiation pattern but employing a loop of length (n+1)#/2 is described with reference to Fig. 3 (Cancelled and not shown). In a further arrangement giving a highly directive beam of radiation in a direction vertically upwards along the axis of the system and which may be employed for feeding a parabolic reflector or for diathermy and therapeutic purposes two peripherally incomplete loops of length n# and fed in phase opposition are spaced apart about the vertical conductive mast by a distance #/2 and a conductive reflector plate is positioned at a distance #/4 below the lower loop (Fig. 4, Cancelled, not shown). In a modification of the latter arrangement a driven peripherally incomplete circular director co-axially disposed outwardly at a fraction of a wavelength from the primary loop is employed to achieve additional vertical directivity (Fig. 5, Cancelled, not shown). In a further arrangement, providing vertical directivity (Fig. 6, Cancelled), a loop radiator 30 of length substantially less than #/2 is brought to the desired electrical length (i.e. #/2) by capacity loading plates 32 and additional vertical directivity is obtained by providing a circular director 35 co-axially with and spaced outwardly from loop 30 by a distance of #/10 to #/2 the director comprising a plurality of elements 36 of length less than #/2 having capacity plates 37 between adjacent ends. To obtain still more vertical directivity with an aerial of the latter type a plurality of assemblies spaced apart vertically by #/2 may be employed (Fig. 9, Cancelled, not shown). This subject-matter does not appear in the Specification as accepted.