Carrier wave recovery system apparatus using synchronous detection

• US 4,143,322 A
• Filed: 09/30/1977
• Issued: 03/06/1979
• Est. Priority Date: 09/30/1976
• Status: Expired due to Term

• Current Assignee: Nippon Electric Company Limited (NEC Corporation)
• Original Assignee: Nippon Electric Company Limited (NEC Corporation)
• Inventors: Shimamura, Tadao
• Primary Examiner(s): Martin, John C.
• Application Number:
  US05/838,173
• Time in Patent Office: 522 Days
• Field of Search: 325/30, 325/320, 325/345, 325/346, 325/349, 325/419, 325/420, 325/423, 178/66 R, 178/66 A, 178/67, 178/88, 329/110, 329/112, 329/122, 329/124, 329/125, 331/9, 331/12, 331/64
• US Class Current: 375/327
• CPC Class Codes: H04L 2027/0048 Frequency multiplication
• CPC Class Codes: H04L 2027/0067 Phase error detectors
• CPC Class Codes: H04L 27/2273 associated with quadrature demodulation, e.g. Costas loop

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.

Claims

1. 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°

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.

2. A carrier wave recovery apparatus as claimed in claim 1 further comprising first and second low pass filter means interposed between said first phase detector and said first comparator, and between said second phase detector and said second comparator.

3. A carrier wave recovery apparatus as claimed in claim 1 further comprising first delay means, connected between said first phase detector and said first subtractor for imparting a delay corresponding to the delay caused by said first comparator, and second delay means, connected between said second phase detector and said second subtractor for imparting a delay corresponding to the delay caused by said second comparator.

4. A carrier wave recovery apparatus as claimed in claim 1 further comprising a first low pass filter connected between said first comparator and said first subtractor, and a second low pass filter connected between said second comparator and said second subtractor.

5. 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°

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.

6. A carrier wave recovery apparatus as claimed in claim 5 further comprising first and second low pass filter means interposed between said first phase detector and said first comparator, and between said second phase detector and said second comparator.

7. A carrier wave recovery apparatus as claimed in claim 5 further comprising first delay means, connected between said first phase detector and said first subtractor for imparting a delay corresponding to the delay caused by said first comparator, and second delay means, connected between said second phase detector and said second subtractor for imparting a delay corresponding to the delay caused by said second comparator.

8. A carrier wave recovery apparatus as claimed in claim 5 further comprising a first low pass filter connected between said first comparator and said first subtractor, and a second low pass filter connected between said second comparator and said second subtractor.