Patent GB-1279861-A (GB)
Title: Method of direction-finding wherein a voltage is produced, the phase position of which in relation to the phase position of a reference voltage represents a measure of the angle of incidence
IPC: G01S3/14
Filed: 1969-07-03
Abstract: 1279861 Radio direction-finders TELEFUNKEN PATENTVERWERTUNGS GmbH 3 July 1969 [5 July 1968] 33649/69 Heading H4D The invention is concerned with a method of direction-finding wherein, from a plurality of voltages corresponding to the angle of incidence α of radio waves, and obtained by means of a crossed direction-finding aerial system, and from an additional voltage of the same frequency which is without directional significance and has the same or opposite phase, a low-frequency voltage is produced, the phase position of which in relation to a reference voltage represents the angle of incidence α. The voltages corresponding to the angle of incidence are added to, and are then subtracted from, the additional non-directional voltage, which is of higher amplitude, within the period of the lowfrequency voltage, to give a resultant voltage or voltages. The low-frequency voltage is obtained from the resultant voltage or voltages by rectification and filtering. In a first embodiment, shown in Fig. 1, two crossed loop aerials 1, 2 are alternately connected during successive intervals of T/4 seconds to one input of a superimposing network 8 by means of a switching device 4. A timing-pulse generator 5 of period T and angular frequency # drives the device 4 through a frequency doubler 6. An auxiliary non- directional aerial 3 is connected through a reversing switch 7, which is directly driven by the generator 5, to the other input of the network 8, which provides an output derived by combining the two inputs in phase or in phase opposition. Said output therefore represents, in successive quarter-periods T/4, (i) signal from aerial 3 plus signal from aerial 1, (ii) signal from aerial 3 plus signal from aerial 2, (iii) signal from aerial 3 minus signal from aerial 1, (iv) signal from aerial 3 minus signal from aerial 2, and, after amplification in an amplifier 9 it is rectified in a network 10 to produce a stepped waveform (Figs. 2(a) to 2(e), not shown). The fundamental signal of angular frequency # is extracted by a filter 11 and is compared in phase with a reference signal from the generator 5 in a network 12. The phase difference between the two signals is related to the angle of incidence α of the radio waves received by the aerials 1, 2, and said angle is indicated by an element 13. In a second embodiment, shown in Fig. 3, the aerials 1, 2 are connected through respective separate channels to a summing network 27, which provides an output for phase comparison to a network 29. The aerial outputs are switched by devices 14, 15 which are driven by a timing pulse generator 5 of period T. Said devices switch the aerials to first inputs of respective superimposing devices 17 or 18 in successive quarter-periods T/4 of (i) normal polarity, (ii) off, (iii) reversed polarity, (iv) off, &c. A device 16 causes the operation of the devices 14, 15 to be staggered by a quarterperiod T/4, or 90 degrees at the angular frequency #. Second inputs to the devices 17, 18 are provided by the auxiliary non-directional aerial 3, and the first inputs are added to or subtracted from them to give outputs which are amplified, rectified and filtered. The resulting two voltage waves of angularfrequency # are added in the network 27 (Figs. 4a to 4e, not shown) and are phase-compared with a reference signal from the generator 5 in the network 29. The indication given by an element 13 is related to the angle of incidence of radio waves upon the aerials 1, 2. Voltages equivalent to those obtained from two perpendicularly disposed direction-finding aerials may be obtained from an aerial system such as a six or eight mast Adcock by means of a co-ordinate transformer. However, in such a case the voltages supplied by the aerials may first of all be added in succession to the associated substantially non-directional voltage, and then be subtracted in succession. Alternatively the voltages obtained at these aerials may be respectively added and subtracted to and from substantially non-direction voltages separately, either the individual additions and subtractions being staggered by #/n (n = number of direction-finding aerials), or an appropriate phase displacement effected later, before the voltages are combined. In using this method, two direction-finding receivers may be used with a single aerial system, by suitably staggering the periods when the aerials are connected to either receiver.