US 2003/0118209 A1 · Data and clock extractor with improved linearity

Abstract

Phase-locked-loop based data and clock extraction comprising a phase detector that generates up and down pulses. Down pulses are maintained in width approximately equal to 1.5 unit intervals of a local sampling clock. Up pulses are allowed to vary with the phase relationship between the local sampling clock and an incoming encoded bit stream. The up pulses are allowed to vary between 1 and 2 unit intervals of the local sampling clock. The up and down pulses drive a charge pump D/A converter that generates a control voltage. The control voltage sets the frequency of the local sampling clock generated by a voltage controlled oscillator. Shift register controlled by a state machine and clocked by the local clock allows reception of complex data packets arriving by the encoded bit stream.

Claims17

Dependent claims

A method for extracting clock and data from an encoded data bit stream comprising the steps of:

generating a local sampling clock;
discovering the difference between the phase of the local sampling clock and the phase of state transitions exhibited by the encoded data bit stream;
creating a down pulse that is maintained at a width greater than a critical value dictated by linearity requirements for a D/A converter;
creating an up pulse that varies in width and is precluded from diminishing in width below a critical value dictated by linearity requirements for a D/A converter;
and
adjusting the frequency of the local sampling clock in relation to the ratio of the width of the down pulse and the up pulse.

3 more elements

A phase-locked-loop comprising:

voltage controlled oscillator that generates a local clock based on a control voltage;
phase detector that receives an encoded bit stream and the local clock and generates a down pulse that is maintained in width and is precluded from narrowing in width below a critical value dictated by linearity requirements for a digital-to-analog converter and
generates an up pulse that varies in width according to the difference in phase between the local clock and state transitions exhibited by the encoded bit stream and is precluded from narrowing in width below a critical value dictated by linearity requirements for a digital-to-analog converter;
and
digital to analog converter that generates the control voltage based on the ratio of the widths of the up and down pulses and that is used as the basis for the frequency of the local clock generated by the voltage controlled oscillator.

2 more elements

A data and clock extraction unit comprising:

voltage controlled oscillator that generates a local clock based on a control voltage;
phase detector that receives an encoded bit stream and the local clock and generates a down pulse that is maintained in width and is precluded from narrowing in width below a critical value dictated by linearity requirements for a digital-to-analog converter and
generates an up pulse that varies in width according to the difference in phase between the local clock and state transitions exhibited by the encoded bit stream and is precluded from narrowing in width below a critical value dictated by linearity requirements for a digital-to-analog converter;
digital to analog converter that generates the control voltage based on the ratio of the widths of the up and down pulses and that is used as the basis for the frequency of the local clock generated by the voltage controlled oscillator;
and
data sampling unit that saves the state of the encoded bit stream coincident with the local clock as a bit of data

3 more elements

Dependencies are inferred from the claim text.

Data and clock extractor with improved linearity

Life of this patent

Data and clock extractor with improved linearity

Life of this patent

Abstract

Claims17