Clock and data recovery scheme for multi-channel data communications receivers

• US 6,307,906 B1
• Filed: 10/07/1998
• Issued: 10/23/2001
• Est. Priority Date: 10/07/1997
• Status: Expired due to Term

• Current Assignee: MACOM Connectivity Solutions, LLC (MACOM Technology Solutions Holdings, Inc.)
• Original Assignee: Applied Micro Circuits Corporation (MACOM Technology Solutions Holdings, Inc.)
• Inventors: Welch, James R., Tanji, Todd M.
• Primary Examiner(s): Pham, Chi
• Assistant Examiner(s): Nguyen, Dung X.
• Application Number:
  US09/168,028
• Time in Patent Office: 1,112 Days
• Field of Search: 375/354, 375/376, 375/326, 375/327, 375/375, 327/148, 359/119, 359/158, 359/189, 359/180, 359/183, 359/187
• US Class Current: 375/376
• CPC Class Codes: H03D 13/004 the logic means delivering pulses at more than one terminal, e.g. up and down pulses
• CPC Class Codes: H03L 7/087 using at least two phase detectors or a frequency and phase detector in the loop
• CPC Class Codes: H03L 7/0891 the up-down pulses controlling source and sink current generators, e.g. a charge pump
• CPC Class Codes: H03L 7/091 the phase or frequency detector using a sampling device H03L7/087 takes precedence
• CPC Class Codes: H03L 7/0995 the oscillator comprising a ring oscillator
• CPC Class Codes: H04L 25/14 Channel dividing arrangements , i.e. in which a single bit stream is divided between several baseband channels and reassembled at the receiver
• CPC Class Codes: H04L 7/033 using the transitions of the received signal to control the phase of the synchronising-signal-generating means, e.g. using a phase-locked loop

Abstract

The multiple-channel clock and data recovery scheme of the present invention derives a single clock signal from multiple mis-matched data streams. The single clock is phased to provide a clocking signal such that the data sampler of the clock and data recovery scheme performs bit center sampling of the data at the bit center average of all channels. The phase of the recovery clock is the average of all the data stream phases, and is the optimal sampling phase for minimum combined bit error rate of all the channels.

Claims

1. A data synchronization system for a fiber optics data communications receiver, the system comprising:

a plurality of input channels;

a plurality of data samplers having at least first and second inputs and an output, wherein each of the first data sampler inputs is connected to an associated input channel;

a plurality of phase detectors having at least first and second inputs and an output, wherein each of the first phase detector inputs is connected to an associated data sampler output; and

a single clock having an input and an output, wherein the clock input is connected to the output of the plurality of phase detectors and the clock output is connected to the second inputs of the plurality of phase detectors and to the second inputs of the plurality of data samplers.

2. The system of claim 1, wherein said single clock comprises a voltage-controlled oscillator and a loop filter operably connected to said voltage-controlled oscillator.

3. The system of claim 1, further comprising a plurality of charge pumps operably connected between the plurality of phase detectors and the single clock.

4. The system of claim 1, wherein said phase detector generates a voltage pulse representative of said phase difference.

5. The system of claim 4, further comprising a charge pump, wherein said charge pump converts said voltage pulse of said phase detector to a current pulse.

6. The system of claim 2, further comprising a charge pump, wherein said phase detector generates a voltage pulse representative of said phase difference, and wherein said charge pump converts said voltage pulse of said phase detector to a current pulse for input to said loop filter.

7. A data synchronization system for a fiber optics data communications receiver, said system comprising:

a plurality of fiber optic data inputs;

a data sampler, wherein said data sampler samples the data from each of said plurality of fiber optic data inputs according to a clock signal from a single clock and produces a data output for each of said plurality of fiber optic data inputs from the sampled data; and

a phase detector, wherein said phase detector compares said data output for each of said plurality of fiber optic data inputs with said clock signal to determine a phase difference between said data output and said clock signal for each of said plurality of fiber optic data inputs;

wherein said single clock averages said phase difference for all of said plurality of fiber optic data inputs to determine an average data center of all of said plurality of fiber optic data inputs and produces said clock signal such that said data sampler samples the data from each of said plurality of fiber optic data inputs at said average data center.

8. The system of claim 7, wherein said single clock comprises a voltage-controlled oscillator and a loop filter operably connected to said voltage-controlled oscillator.

9. The system of claim 7, further comprising a charge pump operably connected between the phase detector and the clock.

10. The system of claim 7, wherein said phase detector generates a voltage pulse representative of said phase difference.

11. The system of claim 10, further comprising a charge pump, wherein said charge pump converts said voltage pulse of said phase detector to a current pulse.

12. The system of claim 8, further comprising a charge pump, wherein said phase detector generates a voltage pulse representative of said phase difference, and wherein said charge pump converts said voltage pulse of said phase detector to a current pulse for input to said loop filter.

13. A data synchronization system for a fiber optics data communications receiver, wherein said fiber optics data communications receiver has a plurality of fiber optic data inputs, said system comprising:

data sampling means for sampling data from each of said plurality of fiber optic data inputs according to a clock signal from a single clocking means and for producing a data output for each of said plurality of fiber optic data inputs from the sampled data; and

phase detecting means for comparing said data output for each of said plurality of fiber optic data inputs with said clock signal and for determining, from the comparison, a phase difference between said data output and said clock signal for each of said plurality of fiber optic data inputs;

wherein said single clocking means is for averaging said phase difference of all of said plurality of fiber optic data input, for determining, from said averaging, an average data center of all of said plurality of fiber optic data inputs, and for producing said clock signal such that said data sampling means samples the data from each of said plurality of fiber optic data inputs at said average data center.

14. The system of claim 13, wherein said single clocking means comprises a voltage-controlled oscillator and a loop filter operably connected to said voltage-controlled oscillator.

15. The system of claim 13, further comprising charge pumping means for converting a pulse of said phase detecting means to a current pulse for input to said loop filter.

16. The system of claim 13, wherein said phase detecting means generates a voltage pulse representative of said phase difference.

17. The system of claim 16, further comprising charge pumping means for converting said voltage pulse of said phase detecting means to a current pulse.

18. The system of claim 14, further comprising charge pumping means, wherein said phase detecting means generates a voltage pulse representative of said phase difference, and wherein said charge pumping means is for converting said voltage pulse of said phase detecting means to a current pulse for input to said loop filter.

19. A method of synchronizing a plurality of fiber optic data inputs, said method comprising the steps of:

sampling data from each of a plurality of fiber optic data inputs according to a single clock signal;

producing a data output for each of said plurality of fiber optic data inputs from the sampled data;

comparing said data output for each of said plurality of fiber optic data inputs with said single clock signal;

determining a phase difference between said data output and said single clock signal for each of said plurality of fiber optic data inputs;

averaging said phase difference of all of said plurality of fiber optic data inputs;

determining an average data center of all of said plurality of fiber optic data inputs; and

producing said single clock signal such that the step of sampling is performed at said average data center.

20. The method of claim 19, further comprising the step of producing a voltage pulse representative of said phase difference.

21. The method of claim 20, further comprising the step of converting said voltage pulse to a current pulse representative of said phase difference.

22. The method of claim 19, further comprising the step of mathematically summing the determined phase differences from each of said plurality of fiber optic data inputs.