GB1259364A - - Google Patents

Abstract

1,259,364. Pulse modulation. COMPAGNIE DES COMPTEURS. 24 March, 1969 [25 March, 1968], No. 15338/69. Heading H3R. [Also in Divisions G1 and G4] A signal generator produces quadrature signals which may represent the components H x , H z of the earth's magnetic field H within a ship's component where the ship is considered to be rolling about an axis Z between limits Œ α at an angular frequency #, the axis Z being at an angle # to the earth's field H. A signal w having an amplitude proportional to α and a frequency equal to the roll frequency # (of the order of 0À01 to 5 c.p.s.) is generated in an oscillator 10 and fed to a phase modulator 12 which is also fed with two signals Œ V sin #t, where # is an arbitrary carrier frequency much higher than #. The signal w is combined with the phase-opposed signals v 0 , v# in the circuits 21, 22, Fig. 4 (this Figure shows details of the modulator 12), which produce pulses whose leading edges are phase modulated in accordance with the signal w (Fig. 3, not shown). These signals are differentiated by RC circuits 23, 24 and fed to two AND circuits 25A, 25B, each having one input connected to the output of the other, which produce an output in the form of rectangular phase-modulated pulses at a frequency #/2#. This signal is integrated in RC circuit 26 and the resultant triangular pulses fed to a resonant circuit 27 which produces a phasemodulated sinusoidal output. The modulator 12 is provided with a phase shifter 13 which produces two outputs in quadrature, viz. where ## = - α sin #t. The source 11 of the carrier signal v also produces four reference signals having phase displacements 0, #/3, 2#/3 and # respectively and one of these signals is fed to a selector 14 which selects a phase # equal to the deviation of the earth's field (see Fig. 1). The phase-adjusted signal is fed to an attenuator 17 to which is applied a variable proportional to the field H. The resultant signal is fed to a phase-splitter 15 which produces two signals in phase opposition, viz. The circuit 16 (details in Fig. 5, not shown) effects addition and subtraction of the above four signals to produce four further signals, viz. These signals are fed to detectors and the detected signals subtracted in pairs to produce the voltages and The values of U 0 , U 1 , U 2 are selected so that the amplitudes of the two signals are both substantially equal to U = 2U 0 as required. The signals may be fed to orthogonal coils which generate the required magnetic field for testing purposes.