Patent GB-574651-A (GB)
Title: Wave-signal direction finder
IPC: G01S3/46
Filed: 1943-05-03
Abstract: 574,651. Sound-ranging. HAZELTINE CORPORATION. May 3, 1943, No. 6993. Convention date, May 23, 1942. [Class 118 (ii)] [Also in Group XL] An apparatus for determining the direction of the source of radiated wave signals, e.g. a machine gun firing at a substantially constant rate, comprises a pair of microphones 11, 12 mounted at opposite ends of a rotatable arm 15 and provided with adjustable-gain arnplifiers 13, 14 connected to the control electrode 29 of a cathode-ray tube 21. The electrostatic deflecting plates 25 receive saw-tooth scanning waves of adjustable frequency from a linescanning generator 26 which may, as described in U.S.A. Specification 2,052,183, comprise a condenser C charged by battery E through a constant current device H having an adjustable tap f for varying the frequency, a vacuum tube S and a feed-back tube RV. The other defleeting plates 27 receive scanning waves from a field-scanning generator 28 similar in construction to the line-scanning generator 26 and connected therewith through a frequency divider 30. One of the amplifiers 13 has a higher gain than that of the other and the spots M on the screen 22 of the tube 21 derived from the microphone 11 are correspondingly brighter than those N from the other microphone so that an indication is given as to which microphone is nearer the sound source. From the amount of separation of the lines M and N, and knowing the frequency of the generator 26 and that of the received sounds, the difference in the distances of the two microphones from the source of sound can be calculated and if this. difference is represented by xz, Fig. 2, the angle wxz between north and the direction of the sound source can be determined, the angle wxy being known and the distance xy being fixed and small compared with the distance of the microphones from the sound source so that the lines S', S<2> from the microphones may be considered parallel. Alternatively, a direct reading may be obtained by a pointer 18 either by swinging the arm 15 so that the lines M, N coincide as at O, where both microphones are at the same distance from the sound source and the arm 15 is normal to S and S<2>, or by swinging the arm so that maximum separation of the lines M, N as at M<1>, N<1> occurs, corresponding to the arm being along the line of direction from the sound source. The inclination of the lines M, N depends on the relative frequencies of the waves applied to the deflecting plates of the cathode-ray tube and the pulses applied to the control electrode 29. The lines are vertical when the line-scanning frequency is substantially equal to an integral multiple of the frequency of the received pulse, sloped as shown when the line-scanning frequency is slightly greater than an integral multiple of the frequency of the received pulse, and sloped reversely when the line-scanning frequency is slightly less than an integral multiple of the frequency of the received pulse. This permits identification of several sounds operating with different frequencies. By using two sets of microphones spaced a known distance d apart, as in Fig. 6, both the direction and the location of the sound source can be determined. Another application of the invention is for determining the position or direction of a ship, the signal of substantially sinusoidal wave form given out by the propeller being picked up and peak-rectified to deliver periodic pulses. The invention may also be applied to lightranging by substituting photo-electric cells for the sound-ranging microphones.