Patent GB-541657-A (GB)
Title: Systems for determining the direction of propagation of electromagnetic waves
IPC: G01S3/12
Filed: 1940-06-01
Abstract: 541,657. Directive wireless systems. STANDARD TELEPHONES & CABLES, Ltd. June 1, 1940, No. 9627. Convention date, June 3, 1939. [Class 40 (v)] In direction-finding systems in which two crossed coils A, B, Fig. 4, connected to directional aerials form the stator of a goniometer whose rotor can be connected to a non-directional aerial at L and feeds a receiver at RR, ambiguity as to the sense of the direction of the source of radiation is resolved by providing the rotor with two or more coils CH1, CH2, CH3, and comparing the levels of two of the signals obtained from different coils so that after the direction has been found, the sense can be determined without further rotation of the rotor. With the arrangement shown in Fig. 4, the control coil CH1 is first used to find the direction DD<SP>1</SP>, Fig. 3, corresponding to minimum reception on the figure-of-eight diagram which is obtained when the non-directional aerial is cut off by the opening of the switch I. The switch I is then closed, so that the non-directional aerial is rendered operative, and coil CH2 is substituted for coil CH1 by operation of switch k, so that a signal whose strength is represented by ON<SP>1</SP> on the cardioid W<SP>1</SP> is picked up by the receiver. Switch k is then moved to select coil CH3, and a signal whose strength is represented by OM<SP>1</SP> is picked up; but if the potentiometer R is so adjusted that the polar diagram is a distorted cardioid W, readings corresponding to ON, OM instead of ON<SP>1</SP>, OM<SP>1</SP>, will be obtained. Two scales graduated in opposite directions are provided, and the reading is taken on one or the other of them, according as one or the other of the switch-settings 2, 3 is the stronger. Instead of three windings, CH1, CH2, CH3, two windings may be employed. The direction DOD<SP>1</SP> may be found with the windings in series, and the levels ON, OM with the separate windings supplemented by a compensating inductance, Fig. 5 (not shown). The Specification as open to inspection under .Sect. 91 also describes the following arrangements : Two windings, Fig. 6 (Cancelled and not :shown) at an acute angle, such as 45 degrees, may be provided ; one of them is used with the figure-of-eight system to find the direction DOD<SP>1</SP> and then with the cardioid system to find the signal-level OP; the other is then used to find the signal-level OM, whence the sense of the direction can be inferred. Alternatively (Fig. 7, Cancelled and not shown) the direction DOD<SP>1</SP> is found with one coil ; then the signal-level along the axis OX<SP>1</SP> of the cardioid is noted with another coil at tight angles to the first, in association with the non-directional aerial ; and finally the signal-level in the opposite direction along the axis OX is noted by means of reversal of the current in the second coil. Instead of the signal-levels such as OM, ON being noted in successive readings, their phase relation may be observed by means of a differential voltmeter or the like, so that the switch k may be dispensed with. Alternatively the coils CH, CH2 may govern the voltages on the deflecting plates of a cathode-ray oscillograph O, Fig. 8 (Cancelled). The direction is formed by cutting off the non-directional aerial at switch I and turning the coils CH1, CH2 until the oscillogram becomes a straight line F inclined at 45 degrees to the axis of the deflecting plates. The switch I is then closed to connect the non-directional aerial, and the sense of the direction is found by noting the direction of movement of the line F. This subject-matter does not appear in the Specification as accepted.