GB579746A - Improvements in or relating to directive electro-magnetic antenna structure - Google Patents

Abstract

579,746. Directive wireless signalling. SPERRY GYROSCOPE CO., Inc. Dec. 4, 1942, No. 17313. Convention date, Jan. 29. [Class 40 (v)] Electromagnetic horns, preferably rectangular in section, are provided with partitions 15<1> ... 18<1> so spaced and arranged that the distribution of the electric field intensity across the mouth of the horn in the plane of polarization is semi-sinusoidal, being substantially zero at the edges of the mouth of the horn and a maximum at its centre. This reduces the secondary lobes present with the simple horn. The partitions 15<1> ... 18<1> and the sides 4<1>, 51 of the horn may be pivoted at their inner ends, the outer ends being connected by links to bars 50 reciprocated by a motor, so that the position of the partitions &c. may be periodically varied to control the direction of maximum transmission. The characteristic pattern of the horn may be modified by introducing waveadjusting means into the inner mouths of the channels defined by the partitions. Such waveadjusting means may comprise rotatable vanes, Fig. 16 (not shown), or gas discharge tubes controlled by a modulated current, Fig. 17 (not shown), or apertured gates controlled by a rotating crank-shaft, Fig. 18 (not shown). Secondary lobes of radiation may be blocked by the use of (1) reflectors 87, 87<1>, Fig. 11, and energy-absorbing means 86, 86<1>, such as a poor conductor arranged between the horn and the reflector, or (2) additional horns 98, 99, Fig. 13, having in their throats discs of carbon 96 or other energy-dissipating material, or (3) corrugated or V-shaped copper reflectors 100, 101, Fig. 14, associated with absorbing material, if desired, or (4) a spherical body completely surrounding the horn except where necessary to permit radiation in the desired direction.