Patent GB-495515-A (GB)
Title: Improvements in and relating to the determination of the direction of incidence of oscillatory phenomena
IPC: G01S1/72
Filed: 1937-12-01
Abstract: 495,515. Locating sounds and like vibrations; wireless signalling. TRIGGS, W. W. (Akt.-Ges. Brown, Boveri, & Cie) Dec. 1, 1937, No. 33279. [A Specification was laid open to inspection under Sect. 91 of the Acts, June 2, 1938.] [Class 118 (ii)] [Also in Group XL] In a method for determining the direction of incidence of oscillations, particularly sound vibrations, two voltages associated with the received oscillations and shifted in phase by 90‹ relative to one another, are caused to modulate one another, the resulting D.C. component corresponding as regards sign and magnitude with the difference in phase of the received sounds. Receivers S1, S2, Fig. 3, feed amplifiers V1, V2 having automatic gain control arrangements R1, R2, the amplified outputs being fed to retarding apparatus L1, L2, which may comprise an acoustic or electric transmission system or a magnetizable steel band passing receiving and transmitting heads. Phase-shifting devices K1, K2 introduce a 90‹ shift so that if the sounds reaching the receivers S1, S2 are in phase, the inputs to the modulator M differ by 90‹ and so have no D.C. output. Otherwise the modulator M gives a D.C. output which, after passing through the low-pass filter B, operates an indicator J. Instead of the devices L1, L2, the receivers S1, S2 may be mounted on a rotatable beam as in Fig. 6. In this modification, the current to the meter J is also fed to a polarized relay R which causes a motor A to rotate to move the receivers S1, S2 into a position where there is a minimum of current. As a preliminary coarse adjustment, the phase shift may be reduced to zero, when the indicator J will give a maximum when the sounds received by S1, S2 are in phase. In a further modification, Fig. 5, a local oscillator O feeds devices D1, D2 which give outputs 90‹ out of phase with respect to one another and fed to auxiliary modulators H1, H2, the output currents from these modulators being fed through low- or high-pass filters P1, P2. Alternatively, condenser microphones may be used as receivers, carrier waves displaced by 90‹ being used instead of a constant bias, the modulators H1, H2 then being unnecessary. Eight receivers S1 ... S8 may be arranged as shown in Fig. 4 feeding retarding devices L1 ... L8 and amplifiers V1 ... V8 so that indicators J<1>, J11 show when a sound source is off a true east-west or north-south course respectively. The retarding devices L1 ... L8 are coupled to rods A<1> and A<11>, the retation of which corrects for any deviations, thus restoring the indicators J<1> and J<11> to zero. In order to indicate wrong adjustments in a northsouth or east-west direction, the voltages may be applied to a cathode-ray tube, the spot moving off-centre when adjustment is needed. In the system as applied to the determination of the direction of incidence of electromagnetic waves, Fig. 9, voltages from spaced aerials S1, S2 are fed through amplifiers to parallel wire systems 5, 6 tapping points 7, 8 being provided to feed the auxiliary modulators H1, H2, the local oscillator O feeding through the network E voltages differing in phase by 90‹. The outputs from modulators H1, H2 are fed to the main modulator M so that by adjusting the tapping points 7, 8, the delay in the wave, reaching aerial S2, may be balanced out, the indicator J then showing a minimum,