Patent GB-1062565-A (GB)
Title: Improvements in or relating to radio direction finding
IPC: G01S3/14
Filed: 1964-01-31
Abstract: 1,062,565. Radio direction finding. ATLASWERKE A.G. Jan. 31, 1964 [Feb. 1, 1963], No. 4244/64. Heading H4D. The invention relates to radio direction finders of the type providing two signals representative of orthogonal components of the incoming signal and producing, by respective application thereof to orthogonal deflection means of a C.R.T., a direction indication. The invention has for its object the reduction of the ellipicity, Fig. 1 (not shown), in the direction indication often found on ship-borne direction finders, wherein reflections, Wave 1, Wave 2, . . . Fig. 3 (not shown), of the incoming wave, Wave 0, of various amplitudes and phases, vectorially add at the antenna to produce a signal representing a wave whose amplitude and direction continuously vary such that the tip of a representative vector describes the indicated ellipse. This resultant wave can either be represented by two positionally orthogonal components which are of different magnitudes and not in phase, or by two oppositely rotating alternating fields D L  and D R  of different magnitudes. The two positionally orthogonal component signals are supplied by the crossed coil antenna, and the invention derives the fields D L  and D R  from those signals and makes the magnitudes of the fields equal, thus enabling the production of the straight line direction indication, Fig. 2 (not shown). The two signals from the antennµ U 1 , U 2 , Fig. 4, are fed to the phase shifters 3 and 4 to produce two signals U 3  and U 4  differing in phase by an angle 90 degrees different from that between U 1  and U 2 , the relative amplitudes being retained. The sum U 5  of signals U 3  and U 4  is produced at 5 and represents D L , and the difference representing D R  is produced at 6. The amplitudes of these two signals are equalized in limiting amplifiers V 7  and V 8 , to produce signals U 7  and U 8 . Signals U 9  and U 10  equivalent to corrected U 1  and U 2  signals are then reproduced by sum and difference circuits 9 and 10. After relative phase shifting by 90 degrees at 11 and 12 to produce signals U 11  and U 12 , these signals are applied to the orthogonal deflection plates of the C.R.T. 13, to produce the straight line direction indication. Alternatively, Fig. 7 (not shown), the fact that the phase differences between U 7  and U 8  represents twice the signal direction α 0  is used. Thus U 7  is fed directly to one input of a subtracting circuit (17), whilst the phase of U 8  is varied, before application to the second input of said circuit, by means of a crossed coil goniometer phaseshifter 16. Thus when the output of circuit 17, as read on means 18, is zero, the position of the rotor of phase shifter 16 represents α 0 . To enable the amount of ellipicity present to be indicated the circuit of Fig. 8 (not shown), is used. Signals U 5  and U 6  are therefore rectified to produce signals U 1  and U 2 , respectively, and sum and difference signals U 3  and U 4  are produced therefrom at 22 and 23. These two signals are converted into A.C. signals of equal frequency and phase but proportional amplitudes, which are applied to a C.R.T. 19, to produce a line having an angle indicative of the degree of ellipicity.