Demodulators – Amplitude modulation demodulator – Having specific distortion – noise or other interference...
Patent
1984-03-07
1986-05-06
LaRoche, Eugene R.
Demodulators
Amplitude modulation demodulator
Having specific distortion, noise or other interference...
329112, 329132, 375 42, 375 81, H03D 300
Patent
active
045874980
ABSTRACT:
A circuit for recovering the carrier of an amplitude-and-phase-modulated input signal (in particular QAM signal) is provided with a frequency-controlled oscillator for producing the carrier, with a quadrature detector for supplying signals representing the amplitude of the input signal projected on two quadrature components P and Q of the carrier signal produced by the oscillator and for thus determining the modulation states of the input signal, and with correction means for forming a correction signal for the frequency control of the oscillator on the basis of output signals from a circuit which determines zones in the plane of the quadrature components P and Q. To provide for a satisfactory operation also in the presence of selective fading, the correction means comprises a weighting circuit connected to the zone-determining circuit for producing the correction signal in accordance with distinct weights allocated to the respective zones defined by the zone-determining circuit.
REFERENCES:
patent: 4334312 (1982-06-01), Yoshida
Bonnerot Georges
Daout Michel
Briody Thomas A.
LaRoche Eugene R.
Pascal Robert J.
Rich Marianne
Streeter William J.
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