Patent GB-563007-A (GB)
Title: Directive antenna system for guiding and direction finding arrangements
IPC: G01S19/09
Filed: 1940-08-21
Abstract: 563,007. Directive wireless signalling. STANDARD TELEPHONES & CABLES, Ltd. Aug. 21, 1940, No. 13291. Convention date, Nov. 7, 1939. [Class 40 (v)] A directive system for defining a twodirectional course by the overlapping beam method, or for use in a direction-finder, comprises a central radiator 101, Fig. 1, and two radiators 102, 103 spaced therefrom, the three radiators being connected by transmission lines 114, 121 to conjugate points of a hybrid bridge 115. In the case of a direction-finder, the other conjugate points are connected to the two channels of the receiver, Fig. 13 (not shown). In the case of a radio-beacon, the other conjugate points are connected to carrierfrequency generators 110,111, Fig. 1, modulated respectively with frequencies F1, F2, and the bridge circuit is such that the antenna 101 is energized over line 114 from the two generators 110, 111 in phase, but the antennµ 102, 103 are energized in phase-opposition (due to the transposition 118 in lines 116, 117) from the generator 110. Similarly, the antennµ 102, 103 are energized in phase-opposition from the generator 111, but owing to the transposition at 120, this energization is in opposite phase with respect to the energy from source 110. Neglecting for the moment the effect of antenna 101, the two radiation patterns 30, 31, Fig. 3, are simultaneously obtained, one modulated with a frequency F1 and the other with frequency F2. These patterns superimposed upon the dumb-bell pattern due to antenna 101 produce an overlapping pattern 40, 41, Fig. 4, defining a two-direction course. The lines 116, 117 are each an odd number of quarter wavelengths long, or they may be a multiple of a half wave-length. Antennµ 102, 103 operate partly as parasitic antennµ energized in phase from antenna 101 and partly as " fed' " antennµ energized in phase opposition over line 121. The individual dipoles may be replaced by antennµ of the kind shown in Fig. 5 and described in Specification 538,036. The two generators 110, 111 may be replaced by a single carrier-frequency generator feeding conjugate points of the bridge 115 over separate modulating means to distinguish the overlapping beams. The course may be further sharpened by additional parasitic antennµ 604, 605, Fig. 7, placed at each side of the beacon 101, 102, 103, and the radiation in a backward direction reduced by a set of parasitic radiators 701, 702, 703 arranged at the back of the beacon and tuned to resonance. In order to avoid distortion due to antennµ 702, 703 being energized in phase by radiation from 101, the antennµ 702, 703 are connected by a transmission line 720 transposed at 721. The antennµ 702, 703 may be tuned by shortcircuiting bars or by a line 730 an integral number of wave-lengths long. Fig. 8 shows the radiation patterns 80, 81 produced by the arrangement of Fig. 7, the field in the backward direction being reduced by antennµ 701, 702, 703. In order to indicate on an aircraft if approach is being made to the side of a beacon, so as to indicate the presence of a landing freld in the vicinity, the three antennµ 101, 102, 103 may be supplemented by auxiliary parasitic antennµ 90, 91, Fig. 9, arranged behind and in front of the central radiator 101. By bringing the antennµ 90, 91 alternately into resonance, the energy in the backward and forward directions is alternately reduced, thus alternately producing the patterns 1000, 1012 and 1011, 1013, Fig. 10. The antennµ 90, 91 may be alternately tuned and detuned by intermittently energizing a relay 1205, Fig. 12, which connects a. tuning line 1203 to the antennµ in turn. Fig. 12 shows in addition a valve circuit 1204 for producing an audio-frequency signal of,. say, 300 cycles for indicating the identity of the beacon, this signal being applied by relay 1206 alternately to the two antennµ 90, 91.