GB563493A - Improvements in or relating to directional aerial systems - Google Patents

Abstract

563,493. Directive wireless systems. CORK, E. C. Sept. 23, 1940, No. 14491. [Class 40 (v)] A directional aerial system comprises three elements, two having a minimum in the same direction and the third a minimum in two opposite directions in the same plane as, and perpendicular to, the first direction, the elements being so arranged that the transmission or reception efficiency increases continuously with angle between the said two opposite directions. The aerial system consists of three radiating elements lying in a single plane and formed by a bent wire ABCDEF, one end A being attached to the inner conductor 1 of the screened feeder 2 and the other end F being connected to earth through a resistance 3 equal to the characteristic impedance of the wire to prevent reflections. The wire is bent into equal loops ABC and DEF at right angles to the length of the wire, the loops forming two of the radiating elements and being equal in length to one quarter of the operating wave-length. The wire CD forming the third radiating element is of a length equal to a quarter of the operating wave-length. The loops ABC and DEF have minimum or zero radiation along the axes of the loops and a maximum in a medial plane normal to the axes. The radiation from the two loops cancels in the direction CD and adds in the direction DC. Radiation from the wire CD is zero in the directions CD and DC, but a maximum in a medial plane normal to CD. In the plane of the bent wire, the total radiation is a maximum in the direction DC, half this maximum in the direction AB, and zero in the direction CD, varying between these limits directly with the angle. To avoid ambiguity, the wire may be associated with a reflector to prevent radiation or reception from unwanted directions. The earth connections shown may be centre tapped half wave-length conductors. The feeder 1,.2 may be coupled to the wire ABC DEF by an impedance matching transformer. Switching means may be provided to interchange the feeder 1, 2 and the resistance 3 so as to reverse the polar diagram. Instead of a bent wire system, separate aerial elements may be fed by separate feeders with appropriate phasing of the currents.