Telecommunications – Transmitter and receiver at separate stations – Distortion – noise – or other interference prevention,...
Patent
1990-01-30
1992-04-28
Eisenzopf, Reinhard J.
Telecommunications
Transmitter and receiver at separate stations
Distortion, noise, or other interference prevention,...
455310, 455317, 329319, H04B 100, H04B 1506
Patent
active
051095327
ABSTRACT:
Phase noise and drift in a broadcast communication system caused by imperfections in transmitter and receiver local oscillators used for up and down conversion of a frequency or phase modulated information signal is eliminated from a downconverted component that is provided for demodulation by adding a pilot frequency component to the modulated signal for mixing by the local oscillator in the transmitter and by frequency locking the local oscillator in the receiver, so that a signal at a frequency equal to the sum of the intermediate frequency and the pilot frequency provided by a phase-locked loop that tracks the pilot frequency component of the downconverted signal is maintained at a desired value. The downconverted signal is mixed with the sum signal provided by the phase-locked loop to provide a component for demodulation at the difference between the pilot frequency and the modulation frequency that is free from the phase noise and drift caused by the local oscillators. Since the phase noise and drift caused by the local oscillators affects the phases of the modulation frequency information component and the pilot frequency component equally, the frequency modulated information is proportional to the difference between the pilot signal frequency and the modulation frequency, and the effect of phase noise and drift is eliminated.
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Fong William
Petrovic Branislav A.
Callan Edward W.
Charouel Lisa
Eisenzopf Reinhard J.
General Instrument Corporation
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