GB600663A - Antenna structure - Google Patents

Abstract

600,663. Aerials ; aerial coupling arrangements. HAZELTINE CORPORATION. Nov. 6, 1944, No. 21782. Convention date, Jan. 4. [Classes 40 (v) and 40 (vii)] In an aerial system for producing a horizontally polarized hemispherical directive characteristic, a folded dipole comprising two horizontal #/2 J-shaped members 42-44 and 45-47, Fig. 4, is backed by a reflector 41 comprising a conductive disc with a diameter of one to four wavelengths and the high impedance of the aerial is matched to the low impedance of the coaxial transmission line 31<11> by means of an impedance matching transformer which may comprise a #/4 transformer 48, 49 as shown or a tapered transmission line. The disc 41 also functions as an earthing screen and is connected at 41a to one conductor 48 of the matching transformer and to the outer conductor of the transmission line, the other conductor 49 of the matching transformer passing through a hole in the disc for connection at 41b to the inner conductor of the transmission line. Suitable dimensions of the systems are given, the diameter of the radiating conductors being preferably #/100 to produce a maximum wide band resonance consistent with the desired radiation characteristic. The folded dipole which without the reflector has a substantially omnidirectional characteristic, is described as a development of the aerial shown in Fig. 1, which comprises two L-shaped #/2 conductors 10, 11 and 12, 13 matched to a transmission line 31 by a #/4 transformer 14, 15, the aerial elements and transformer being supported rigidly by the insulating spacers 16, 17, 18 and 21. The aerial is supported on a hollow metal mast 30 by means of a socket in the junctionbox 25 attached to the back plate 18 and the transformer is connected to a coaxial or open wire feeder enclosed in the mast, Fig. 1a (not shown). The structural features described in connection with this aerial are stated to be applicable to the embodiment of the aerial shown in Fig. 4.