US4297650A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Phase locked loop carrier recovery circuit with false lock prevention
Assignee: NEC Corp
•
Filing: 1979-12-27
•
Granted: 1981-10-27
•
Expires: 1999-12-27
Abstract
Abstract A carrier recovery apparatus for phase modulated waves including phase-locked loops is operable to prevent false locks. The apparatus includes a clock recovery circuit which generates a signal in response to a modulated carrier, a first phase comparator responsive to the modulated carrier and the output of a VCO, a second phase comparator responsive to the first phase comparator and the clock signal, and a control device for superimposing the low frequency component of the output of the second phase comparator on the output of the first phase comparator or a loop filter which controls the VCO.
Inventors
- 👤 Saburo Shinmyo
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 16:23
CPC Classifications
H; H03; H03L; H03L7/00; H03L7/06; H03L7/08; H03L7/10; H03L7/101; H03L7/102; H03L7/085; H03L7/087; H04; H04L; H04L27/00; H04L27/18; H04L27/22; H04L27/227; H04L27/2271; H04L27/2272; H10; H10P; H10P95/00; H10P95/90; H03L2207/00; H03L2207/14; Y; Y10; Y10S; Y10S331/00; Y10S331/02
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
147 words
A carrier recovery apparatus comprising an input terminal for receiving a phase-modulated carrier, a voltage-controlled oscillator for generating a variable frequency oscillation in response to a control signal, a first phase comparator for providing a comparison output representative of the phase difference between said modulated carrier and the output of said voltage-controlled oscillator, a loop filter for supplying said voltage-controlled oscillator with the low-frequency component of the output of said first phase comparator as said control signal, a clock recovery circuit for generating a clock signal in response to said modulated carrier, a second phase comparator for providing a comparison output representative of the phase difference between the output of said first phase comparator and said clock signal, and means for superimposing the low-frequency component of the output of said second phase comparator on one of the outputs of said first phase comparator and said loop filter.
Claim 2
Dependent Claim
147 words
A carrier recovery apparatus comprising an input terminal for receiving a phase-modulated carrier, a voltage-controlled oscillator for generating a variable frequency oscillation in response to a control signal, a first phase comparator for providing a comparison output representative of the phase difference between said modulated carrier and the output of said voltage-controlled oscillator, a loop filter for supplying said voltage-controlled oscillator with the low-frequency component of the output of said first phase comparator as said control signal, a clock recovery circuit for generating a clock signal in response to said modulated carrier, a second phase comparator for providing a comparison output representative of the phase difference between the output of said first phase comparator and said clock signal, and means for superimposing the low-frequency component of the output of said second phase comparator on one of the outputs of said first phase comparator and said loop filter.
Claim 3
Dependent Claim
72 words
A carrier recovery circuit as claimed in claim 1 wherein said second phase comparator comprises a mixer for mixing said clock signal and said comparison output from said first phase comparator, and a low pass filter for passing to an output thereof the low frequency component of said mixer whereby said low frequency component indicates the existence of and direction for correction of a false phase lock in said carrier recovery apparatus.
Claim 4
Dependent Claim
25 words
A carrier recovery circuit as claimed in claim 1 or 2 wherein said low frequency component is superimposed on the output of said loop filter.
Claim 5
Dependent Claim
45 words
A carrier recovery circuit as claimed in claim 1 or 2 wherein said first phase comparator includes a multiplier means for multiplying said comparison output from said first phase comparator by N where N is the number of distinct phases in the phase modulated carrier.
Claim 6
Dependent Claim
23 words
A carrier recovery circuit as claimed in claim 4 wherein said low frequency component is superimposed on the output of said multiplier means.
Claim 7
Dependent Claim
48 words
A carrier recovery apparatus as claimed in claim 1 or 2, wherein said means for superimposing has a high impedance when the carrier recovery apparatus is in the desired phase locked condition, and a lower impedance when the carrier recovery apparatus is in a false phase locked condition.
References Cited (Backward Citations)
US3768030A
Cited
US4000476A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-10-26 | 1985-04-27 | 1985-10-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-10-26 | 1989-04-27 | 1989-10-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-10-26 | 1993-04-27 | 1993-10-27 | $7700.00 | Window Closed / Lapsed |