Process for the demodulation of an amplitude modulated signal and demodulator performing this process

Abstract

A process for the demodulation of an amplitude modulated signal composed of two suppressed carriers, at a same frequency F and in phase quadrature, which are respectively modulated by two modulation signals, the modulated signal being preceded by a reference signal at frequency F, by sampling the reference signal and the modulated signal, according to a frequency m.F (m being an integer); determining a polar angle .psi..sub.t of a rotating vector representing the reference signal, at time t, by calculating: ##EQU1## where x(t) and x(t-(1/4F)) are the values of two successive samples of the reference signal; determining polar coordinates (.rho..sub.t, .theta..sub.t) of a rotating vector representing the modulated signal, at time t, by calculating: ##EQU2## where y(t) and y(t-(1/4F)) are values of two successive samples of the modulated signal, calculating .gamma.=.theta..sub.t -.omega..sub.t -.phi..sub.o, where .phi..sub.o is the phase displacement between the reference signal and one of the carriers, calculating .alpha.=.rho..sub.t.cos .gamma. .beta.=.rho..sub.t.sin .gamma. and generating two signals whose instantaneous amplitudes are .alpha. and .lambda..beta..

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