Patent US2975711A successfully refreshed from Google Patents.
EP0502739A2
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EP
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NRZ clock and data recovery system employing phase lock loop
Assignee: Grass Valley Group Inc
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Filing: 1992-03-05
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Granted: —
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Expires: 2012-03-05
Abstract
Abstract An improved NRZ clock and data recovery system lends itself to integration, includes a NRZ phase detector, an NRZ frequency detector and a lock detector, and provides automatic centering of the clock edge within the bit interval in a manner that is independent of analog delays and process and temperature variations. NRZ data is applied to one side of an exclusive-OR gate (6) and a twice delayed (2, 4) version of the NRZ data is applied to the other side. The output of the XOR gate (6), a "blivet" signal, is applied to a NRZ phase detector (10) comprising two AND gates (12,14), one of which (12) has as its other input a recovered clock signal output of a VCO (20) and the other of which has as its other input an inverted (16) version of the recovered clock signal. The "up" and "down" outputs of the AND gates (10,12) indicate which direction a frequency control signal (26) should change the VCO (20) frequency. A data holding flip-flop (28) whose input is a once delayed (2) version of the NRZ data is clocked with the recovered clock signal. The NRZ frequency detector (50) monitors the state of the recovered clock signal on opposite edges (52,53) of the blivet to detect too-high (56), too low (55) and good (54) conditions. The results of the detection can be ignored if a lock signal indicates that the phase lock loop is locked. The lock detector (30) consists of a saturating up/down counter (42) that is incremented (38) by one when good blivets (32) occur and is decremented (40) by four when not-good blivets (36) occur.
Inventors
- 👤 David L. Hershberger
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-01 17:08
CPC Classifications
H; H03; H03L; H03L7/00; H03L7/06; H03L7/08; H03L7/085; H03L7/089; G; G11; G11B; G11B20/00; G11B20/10; G11B20/14; G11B20/1403; G11B20/1407; G11B20/1419; H03L7/087; H03M; H03M5/00; H03M5/02; H03M5/04; H03M5/14; H04; H04L; H04L7/00; H04L7/0079; H04L7/0087; H04L7/02; H04L7/033; Y; Y10; Y10S; Y10S331/00; Y10S331/02
Claims Analysis
Total Claims: 42
Claim 1
Independent Claim
73 words
An NRZ clock recovery system comprising: a blivet generator (8) coupled to receive an NRZ input and producing a blivet signal in response to a transition of the NRZ input; a controllable oscillator (20) coupled to receive an oscillator control signal and producing a recovered NRZ clock signal; and a control signal generator (10, 26) coupled to receive the recovered NRZ clock signal and the blivet signal and producing the oscillator control signal.
Claim 2
Dependent Claim
70 words
An NRZ clock recovery system according to claim 1 wherein the blivet generator (8) comprises: a delay element (2,4) coupled to receive an NRZ input and producing a delayed NRZ output; and an exclusive-OR gate (6) coupled to receive the NRZ input and the delayed NRZ output and producing a blivet signal when the stade of the NRZ input is different from the state of the twice delayed NRZ output.
Claim 3
Dependent Claim
58 words
An NRZ clock recovery system according to claim 2 wherein the delay element comprises: a first delay element (2) coupled to receive the NRZ input and producing a once delayed NRZ output; and a second delay element (4) coupled to receive the once delayed NRZ output of the first delay element and producing a twice delayed NRZ output.
Claim 4
Dependent Claim
22 words
An NRZ clock recovery system according to claim 3, wherein the first (2) and second (4) delay elements produce substantially equal delays.
Claim 5
Dependent Claim
65 words
An NRZ clock recovery system according to claim 1 wherein the control signal generator (10,26) comprises: a phase detector (10) coupled to receive the recovered NRZ clock signal and the blivet signal and producing an up signal and a down signal; and oscillator control means (26) coupled to receive the up and down signals from the phase detector (10) and producing the oscillator control signal.
Claim 6
Dependent Claim
117 words
An NRZ clock recovery system according to claim 5, wherein the phase detector (10) comprises: first gating means (12) coupled to receive the recovered NRZ clock signal and the blivet signal and producing an up output while the state of the recovered NRZ clock signal is the same as the state of the blivet signal; an inverter (16) coupled to receive the recovered NRZ clock signal and producing an inverted recovered NRZ clock signal; and second gating means (14) coupled to receive the inverted recovered NRZ clock signal and the blivet signal and producing a down signal while the state of the inverter recovered NRZ clock signal is the same as the state of the blivet signal.
Claim 7
Dependent Claim
76 words
An NRZ clock recovery system according to claim 1 further comprising: a frequency detector (50) coupled to receive the recovered NRZ clock signal and the blivet signal and producing an up signal and a down signal; and up/up-down/down combining means (24,22), coupled to receive the up and down signals from the phase detector (10) and the up and down signals from the frequency detector (50) and producing a combined up signal and a combined down signal.
Claim 8
Dependent Claim
77 words
An NRZ clock recovery system according to claim 7, wherein the frequency detector (50) comprises: means for determining (52,51,53) the states of the clock signal at the times that blivet edges occur; and means for ascertaining (55,56) from the determined states when the frequency of the recovered NRZ clock signal is apparently low or apparently high, and producing the up signal when the frequency is apparently low and the down signal when the frequency is apparently high.
Claim 9
Dependent Claim
62 words
An NRZ clock recovery system according to claim 8, wherein the means for ascertaining comprises: means for ignoring (55,62,63) an apparently low frequency when the result of an immediately preceding ascertaining was that the frequency was apparently high; and means for ignoring (56,60,61) an apparently high frequency when the result of the immediately preceding ascertaining was that the frequency was apparently low.
Claim 10
Dependent Claim
43 words
An NRZ clock recovery system according to claim 7, wherein the frequency detector (50) is further coupled to receive a lock signal, and while the lock signal is active the frequency detector does not produce (58,59) the up signal or the down signal.
Claim 11
Dependent Claim
66 words
An NRZ clock recovery system according to claim 7, wherein the frequency detector (50) further produces (54,57) a not-good blivet signal and wherein the system further comprises: a lock detector (30) coupled to receive the blivet signal and the not-good blivet signal and producing a lock signal when the number of blivet signals received bears a predetermined relationship to the number of not-good blivet signals received.
Claim 12
Dependent Claim
51 words
An NRZ clock recovery system according to claim 11, wherein the lock detector (30) comprises: a saturating up/down counter (42), the counter incrementing (38) by a first constant in response to each good blivet (32,34) signal and decrementing (40) by a second constant in response to each not-good (36) blivet signal.
Claim 13
Dependent Claim
43 words
An NRZ clock recovery system according to claim 4 further comprising: means for recovering data (28) coupled to receive the once delayed NRZ output of the first delay element (2) and the recovered NRZ clock (20) and producing a recovered NRZ data output.
Claim 14
Dependent Claim
68 words
An NRZ clock and data recovery system according to claim 13 wherein the means for recovering NRZ data (28) comprises: means for holding data (28) having a data input and a clock input, the data input being coupled to receive the once delayed NRZ output and the clock input being coupled to receive the recovered NRZ clock signal, the holding means (28) producing the recovered NRZ data output.
Claim 15
Dependent Claim
101 words
An NRZ frequency detector (50) for a phase lock loop circuit, the NRZ frequency detector having a first terminal for receiving a blivet signal and a second terminal for receiving a clock signal, the NRZ frequency detector comprising: means for determining (52,53) the states of the clock signal at the times that edges of the blivet signal occur; and means for ascertaining (55,56) from the determined states when the frequency of the clock signal is apparently low or apparently high, and producing a too-low signal when the frequency is apparently low and a too-high signal when the frequency is apparently high.
Claim 16
Dependent Claim
122 words
An NRZ frequency detector according to claim 15, wherein the means for determining comprises: a first flip-flop (52) having the clock signal as a data input and the blivet signal as a clock input, the first flip-flop (52) producing a first indication signal if the clock signal was high at the time of a first edge of the blivet signal; an inverter (51) coupled to receive the blivet signal and producing an inverted blivet signal; and a second flip-flop (53) having the clock signal as a data input and the inverted blivet signal as a clock input, the second flip-flop producing a second indication signal if the clock signal was high at the time of a second edge of the blivet signal.
Claim 17
Dependent Claim
118 words
An NRZ frequency detector according to claim 15, wherein the means for ascertaining comprises: first gating means (55) coupled to receive a first indication signal if the clock signal was high at a time of a first edge of the blivet signal and a second indication signal if the clock signal was high at a time of a second edge of the blivet signal, the first gating means (55) producing a too-low signal if the first and second indication signals are both active; and second gating means (56) coupled to receive the first indication signal and the second indication signal, the second gating means producing a too-high signal if the first and second indication signals are both inactive.
Claim 18
Dependent Claim
34 words
An NRZ frequency detector according to claim 17, wherein the means for ascertaining further comprises: means for holding (58) a previously produced too-low signal; and means for holding (59) a previously produced too-high signal.
Claim 19
Dependent Claim
52 words
An NRZ frequency detector according to claim 18 further comprising a lock signal generating means (30), and the means for ascertaining (55,56,58,59) is coupled (58,59) to receive the lock signal and while the lock signal is active the means for ascertaining does not produce (58,59) the up signal or the down signal.
Claim 20
Dependent Claim
63 words
An NRZ frequency detector according to claim 18, wherein the means for ascertaining (55,56,58,59) further comprises: means for ignoring (55,62,63) an apparently low frequency when the result of an immediately preceding ascertaining was that the frequency was apparently high; and means for ignoring (56,60,61) an apparently high frequency when the result of the immediately preceding ascertaining was that the frequency was apparently low.
Claim 21
Dependent Claim
118 words
A lock detector (30) for a phase lock loop circuit, the lock detector having a first terminal for receiving blivet pulses and a second terminal for receiving not-good pulses, the lock detector (30) comprising: a saturating up/down counter (42); means for incrementing (38) the counter by a first constant in response to each blivet pulse that is not accompanied by a not-good pulse (32,34); means for decrementing (40) the counter by a second constant in response to each blivet that is accompanied by a not-good pulse (36); and means for determining (44) if a count in the counter (42) is above a predetermined threshold value and producing a lock signal when the count is above the predetermined threshold.
Claim 22
Independent Claim
58 words
A method for NRZ clock recovery comprising comprising the steps of: generating a blivet (8) in response to a transition of an NRZ input; producing a recovered NRZ clock signal (20) according to an oscillator control signal; and generating a control signal (10,26) based on the timing relationship between the recovered NRZ clock signal and the blivet signal.
Claim 23
Dependent Claim
56 words
A method for NRZ clock recovery according to claim 22 wherein the step of generating a blivet (8) comprises the steps of: delaying (2,4) an NRZ input to produce a delayed NRZ output; and producing (6) a blivet signal when the state of the NRZ input is different from the state of the delayed NRZ output.
Claim 24
Dependent Claim
47 words
A method for NRZ clock recovery according to claim 23 wherein the delaying step comprises the steps of: delaying once (2) the NRZ input to produce a once delayed NRZ output; and delaying again (4) the once delayed NRZ output to produce a twice delayed NRZ output.
Claim 25
Dependent Claim
26 words
A method for NRZ clock recovery according to claim 24 wherein the delaying once step (2) and the delaying again step (4) produce substantially equal delays.
Claim 26
Dependent Claim
63 words
A method for NRZ clock recovery according to claim 22 wherein the step of generating a control signal (10,26) comprises: detecting a phase relationship (10) between the recovered NRZ clock signal and the blivet signal and producing an up signal and a down signal according to the detected relationship; and producing an oscillator control signal (26) according to the up and down signals.
Claim 27
Dependent Claim
70 words
A method for NRZ clock recovery according to claim 26 wherein the step of detecting a phase relationship (10) comprises: producing (12) an up output while the state of the recovered NRZ clock signal is the same as the state of the blivet signal; and producing (14) a down signal while the state of an inverted recovered NRZ clock signal is the same as the state of the blivet signal.
Claim 28
Dependent Claim
76 words
A method for NRZ clock recovery according to claim 22 further comprising the steps of: detecting a frequency relationship (50) between the recovered NRZ clock signal and the blivet signal to produce an up signal and a down signal; and combining (24,22) the up and down signals from the phase detecting step (10) and the up and down signals from the frequency detecting step (50) to produce a combined up signal and a combined down signal.
Claim 29
Dependent Claim
79 words
A method for NRZ clock recovery according to claim 28, wherein the detecting step (50) comprises the steps of: determining (52,51,53) the states of the recovered NRZ clock signal at the times that blivet edges occur; and ascertaining (55,56) from the determined states when the frequency of the recovered NRZ clock signal is apparently low or apparently high, to produce the up signal when the frequency is apparently low and the down signal when the frequency is apparently high.
Claim 30
Dependent Claim
65 words
A method for NRZ clock recovery according to claim 29, wherein the step of ascertaining comprises the steps of: ignoring (55, 62,63) an apparently low frequency when the result of an immediately preceding ascertaining step was that the frequency was apparently high; and ignoring (56,60,61) an apparently high frequency when the result of the immediately preceding ascertaining step was that the frequency was apparently low.
Claim 31
Dependent Claim
40 words
A method for NRZ clock recovery according to claim 28, wherein the detecting step (50) further comprises the steps of: receiving a lock signal; and not producing the up signal or the down signal while the lock signal is active.
Claim 32
Dependent Claim
54 words
A method for NRZ clock recovery according to claim 28, wherein the detecting step (50) further comprises the steps of: generating a not-good blivet (54,57); and detecting a lock (30) to produce a lock signal when the number of blivet signals received bears a predetermined relationship to the number of not-good blivet signals received.
Claim 33
Dependent Claim
60 words
A method for NRZ clock recovery according to claim 32 wherein the detecting a lock step (30) comprises the step of: incrementing (38) a saturating up/down counter (42) by a first constant in response to each good blivet (32,34) signal; and decrementing (40) the saturating up/down counter (42) by a second constant in response to each not-good (36) blivet signal.
Claim 34
Dependent Claim
26 words
A method for NRZ clock recovery according to claim 25 further comprising the step of: recovering (28) NRZ data to produce a recovered NRZ data output.
Claim 35
Dependent Claim
66 words
A method for NRZ clock and data recovery according to claim 34 wherein the recovering step (28) comprises the steps of: receiving the once delayed NRZ output from the delaying once step (2) at an input of a means for holding data; and clocking the once delayed NRZ output from the delaying once step into the means for holding data using the recovered NRZ clock (20).
Claim 36
Independent Claim
76 words
A method for NRZ frequency detecting in a phase lock loop circuit, the method comprising the steps of: determining (52,53) the stades of a clock signal at the times that edges of a blivet signal occur; and ascertaining (55,56) from the determined states when the frequency of the clock signal is apparently low or apparently high, producing a too-low signal when the frequency is apparently low and a too-high signal when the freqency is apparently high.
Claim 37
Dependent Claim
76 words
A method for NRZ frequency detecting according to claim 36, wherein the determining step comprises the steps of: producing (52) a first indication signal if the clock signal was high at the time of a first edge of the blivet signal; inverting (51) the blivet signal to produce an inverted blivet signal; and producing (53) a second indication signal if the clock signal was high at the time of a second edge of the blivet signal.
Claim 38
Dependent Claim
114 words
A method for NRZ frequency detecting according to claim 36 wherein the step of ascertaining comprises the steps of: ANDing (55) a first signal indicating if the clock signal was high at a time of a first edge of the blivet signal with a second signal indicating if the clock signal was high at a time of a second edge of the blivet signal to produce a too-low signal if the first and second indication signals are both active; and ANDing (56) an inverted version of the first indicating signal with an inverted version of the second indicating signal to produce a too-high signal if the first and second indicating signals are both inactive.
Claim 39
Dependent Claim
35 words
A method for NRZ frequency detecting according to claim 37 wherein the step of ascertaining further comprises the steps of: holding (58) a previously produced too-low signal; and holding (59) a previously produced too-high signal.
Claim 40
Dependent Claim
37 words
A method for NRZ frequency detecting according to claim 39 further comprising the step of: generating a lock signal (30); and not producing (58,59) the too-low signal or the too-high signal while the lock signal is active.
Claim 41
Dependent Claim
66 words
A method for NRZ frequency detecting according to claim 39 wherein the step of ascertaining (55,56,58,59) further comprises the steps of: ignoring (55,62,63) an apparently low frequency when the result of an immediately preceding ascertaining step was that the frequency was apparently high; and ignoring (56,60,61) an apparently high frequency when the result of the immediately preceding ascertaining step was that the frequency was apparently low.
Claim 42
Independent Claim
100 words
A method of lock detecting (30) for a phase lock loop circuit, the method comprising the steps of: incrementing (38) a saturating up/down counter (42) by a first constant in response to a blivet pulse that is not accompanied by a not-good pulse (32,34); decrementing (40) the saturating up/down counter (42) by a second constant in response to a blivet pulse that is accompanied by a not-good pulse (36); and determining (44) if a count in the saturating up/down counter (42) is above a predetermined threshold value to produce a lock signal when the count is above the predetermined threshold.
References Cited (Backward Citations)
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