GB525182A - Method of and means for determining directly a bearing by means of a radio beacon - Google Patents

Abstract

525,182. Directive wireless systems. STANDARD TELEPHONES & CABLES, Ltd., and EARP, C. W. Feb. 17, 1939, No. 5324. [Class 40 (v)] The angular bearing (or elevation) of a moving craft relatively to a distant transmitter is obtained by comparing the signals from two overlapping beams, differently modulated, with signals containing the same modulation frequencies on a different carrier and transmitted simultaneously from a non-directional aerial. In Fig. 1, two portions of the output from the carrier wave generator C1 are separately modulated in the balanced modulators M1, M2 with different frequencies fl(t), f2(t) generated by the oscillators O1 and O2, the modulation products being fed to the crossed loops L1, L2 respectively. A non-directional comparison signal comprising a carrier of different frequency generated at C2 and modulated at M3 with both of the frequencies fl(t), f2(t) is radiated from the open aerial VI and if the overlapping characteristics are to be of the cardioid form another portion of the output from the generator C1 is also radiated from the aerial VI. At the receiver, the signals of carrier frequency C1 are amplified at A1, Fig. 2, and after detection at D1 a low-frequency signal of the form sin f1t cos # + sin f2t cos (#+90), where # is the bearing of the receiver from the loop L1, is applied to the movable coil S of a dynamometer B. Meanwhile the signal of carrier frequency C2 is amplified at A2 and after detection at D2 the two modulation frequencies fl, f2 are separated by the filters F1, F2 and applied to the field-coils X, Y. The resultant deflection of the coil S then indicates the bearing angle #. Alternatively, the connections from the detectors D1, D2 to the dynamometer may be reversed. Or a cathode-ray indicator ,can be used as described in Specification 490,940, in which case the two modulation frequencies derived from the non-directional signal are applied to the deflection plates, and the modulation components obtained from the directional signals are used to control the intensity of the electron beam. Modulating wave forms other than sinusoidal may be employed.