| 摘要 |
<p>1. A digital demodulator for demodulating a signal xs (t) which is frequency modulated around a frequency F, or a signal xp (t) which is modulated in amplitude and which results from an amplitude modulation of two carriers of identical frequency F and of phase quadrature by two modulation signals, followed by a carrier suppression, this demodulator comprising a sampler (3) applied to the signal which is to be demodulated, an analog-digital-converter (4) to which the samples selected by the sampler are applied, a delay circuit (5, 6) coupled to the output of the converter (4), a device (10, 11, 12) for determining the module and the phase of the vector Z(t) which is representative for the signal to be demodulated, this device having first (31) and second outputs (32) furnishing respectively the module and the phase of the vector Z(t), and first computer means (B) for determining the frequency variation of the signal xs (t) as a function of the phase variations of the vector Z(t), characterized in that the sampler has a sampling frequency of 4F, that the delay circuit comprises a first delay member (5) having a delay THETA 1 equal to 1/4F, and having an input which is coupled to the output of the converter (4), and a second delay member (6) of a delay THETA 1 , having an input which is coupled to the output of the first delay member, that the device for determining the module and the phase of the vector Z(t) comprises first, second and third inputs, which are coupled respectively to the output of the converter (4), to the output of the first delay member (5) and to the output of the second delay member, and that the demodulator comprises second computer means (C) for determining the amplitudes alpha and beta of the two modulation signals of the signal xp (t) as a function of the values of the module and of the phase of the vector Z(t).</p> |
