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US 4,143,322 AGranted
Carrier wave recovery system apparatus using synchronous detection
AssigneeNippon Electric Co., Ltd.
InventorTadao Shimamura
Life of this patent
Estimating the term…
Abstract
A carrier wave recovery apparatus of the decision feedback type having analog multipliers of lower dynamic range. The modulated signal is phase detected by comparison with a VCO signal. The analog multipliers receive a signal derived by subtraction of the phase detected signal from the same phase detected signal compared with a reference. That signal is multiplied in an analog multiplier by the phase detected signal or by the signal produced from comparing the phase detected signal with a reference.
Claims8
A carrier wave recovery apparatus comprising:
- an input terminal for receiving a carrier-suppressed modulated signal;
- a voltage controlled oscillator forming a source of a carrier wave for demodulation of said modulated signal;
- first and second phase detector means supplied with the output of said voltage controlled oscillator directly and through a 90.degree. phase shifter, respectively, for demodulating said modulated signal;
- first and second comparator means for determining the polarity of the output voltages of said first and second phase detector means with respect to a reference voltage and for providing a predetermined output voltage of a polarity depending on the determined polarity;
- a first subtractor for providing the difference between the outputs of said first phase detector and said first comparator;
- a second subtractor means for providing the difference between the output of said second phase detector and said second comparator;
- a first analog multiplier means for multiplying the outputs of said first subtractor and said second comparator;
- a second analog multiplier means for multiplying the outputs of said second subtractor and said first comparator;
- a third subtractor means for providing the difference between the outputs of said first and said second multipliers;
- and means for supplying the output of said third subtractor to said voltage controlled oscillator for phase control.
7 more elements
A carrier wave recovery apparatus comprising:
- an input terminal for receiving a carrier-suppressed modulated signal;
- a voltage controlled oscillator forming a source of a carrier wave for demodulation of said modulated signal;
- first and second phase detector means supplied with the output of said voltage controlled oscillator directly and through a 90.degree. phase shifter, respectively, for demodulating said modulated signal;
- first and second comparator means for determining the polarity of the output voltages of said first and second phase detector means with respect to a reference voltage and for providing a predetermined output voltage of a polarity depending on the determined polarity;
- a first subtractor means for providing the difference between the outputs of said first phase detector and said first comparator;
- a second subtractor means for providing the difference between the output of said second phase detector and said second comparator;
- a first analog multiplier means for multiplying the outputs of said first subtractor and said second phase detector;
- a second analog multiplier means for multiplying the outputs of said second subtractor and said first phase detector;
- a third subtractor means for providing the difference between the outputs of said first and said second multipliers;
- and means for supplying the output of said third subtractor to said voltage controlled oscillator for phase control.
7 more elements
Dependencies are inferred from the claim text.