# US 7,613,093 B2 · Duty ratio control apparatus for pre-pit detection or header detection of an optical storage medium

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- Number: US 7,613,093 B2
- Document ID: US7613093B2
- Status: Granted
- Kind: B2
- Application number: 11/162,948
- Filed: 2005-09-28
- Published: 2007-03-29
- Granted: 2009-11-03
- Earliest claimed: 2005-09-28
- Assignees: Mediatek Inc.
- Inventors: Bing-Yu Hsieh; Chih-Ching Chen
- Web page: https://patentgrep.com/patent/US7613093B2

## CPC

- G11B 7/00745: {Sectoring or header formats within a track (formats in general G11B20/12)}
- G11B 7/0912: {by push-pull method}
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)

## Abstract

A pre-pit signal generating device includes: a first slicer for generating a sliced signal corresponding to a push-pull signal based on a first reference level; a duty ratio controller coupled to the first slicer for adjusting the first reference level or the push-pull signal to control a duty ratio of the sliced signal to a predetermined ratio; a reference level generator coupled to the duty ratio controller for generating a second reference level corresponding to the first reference level; and a second slicer coupled to the reference level generator for generating a first pre-pit signal corresponding to the push-pull signal based on the second reference level.

## Claims

### Claim 1

A pre-pit signal generating device comprising:
a first slicer for generating a sliced signal corresponding to a push-pull signal and a first reference level;
a duty ratio controller coupled to receive the sliced signal for adjusting the first reference level or the push-pull signal to control a duty ratio of the sliced signal to a predetermined ratio;
a reference level generator coupled to receive the first reference level output from the duty ratio controller for generating a second reference level corresponding to the first reference level; and
a second slicer coupled to receive the second reference signal and the push-pull signal for generating a first pre-pit signal corresponding to the push-pull signal and the second reference level.

### Claim 2 (depends on 1)

The pre-pit signal generating device of claim 1, wherein the reference level generator generates a third reference level corresponding to the first reference level, and the pre-pit signal generating device further comprises:
a third slicer coupled to receive the third reference signal and the push-pull signal for generating a second pre-pit signal corresponding to the push-pull signal and the third reference level.

### Claim 3 (depends on 2)

The pre-pit signal generating device of claim 2, wherein the first pre-pit signal is for decoding address information of an optical storage medium, the second pre-pit signal is for generating a recording/reproducing clock signal.

### Claim 4 (depends on 1)

The pre-pit signal generating device of claim 1, wherein the duty ratio controller comprises:
a duty detector coupled to the first slicer for detecting the duty ratio of the sliced signal; and
an adjusting device coupled to the duty detector for adjusting the first reference level or the push-pull signal according to the detecting result of the duty detector.

### Claim 5 (depends on 4)

The pre-pit signal generating device of claim 4, wherein the duty detector comprises:
a sampling unit for sampling the sliced signal to generate a sampled signal; and
a counter coupled to the sampling unit and the adjusting device for determining the detecting result by counting the sampled signal.

### Claim 6 (depends on 4)

The pre-pit signal generating device of claim 4, wherein the duty detector comprises:
a low-pass filter for low-pass filtering the sliced signal to generate a filtered signal; and
a comparator coupled to the low-pass filter and the adjusting device for determining the detecting result by comparing the filtered signal with a predetermined value.

### Claim 7 (depends on 4)

The pre-pit signal generating device of claim 4, wherein the adjusting device is a charge pump or an analog integrator.

### Claim 8 (depends on 4)

The pre-pit signal generating device of claim 4, wherein the adjusting device comprises:
a decision unit coupled to the duty detector for generating a first control value according to the detecting result of the duty detector; and
a first digital-to-analog converter (DAC) coupled to the decision unit for adjusting the first reference level according to the first control value.

### Claim 9 (depends on 8)

The pre-pit signal generating device of claim 8, wherein the decision unit is a counter or a digital integrator.

### Claim 10 (depends on 8)

The pre-pit signal generating device of claim 8, wherein the reference level generator comprises:
a first computing unit coupled to the decision unit for adjusting the first control value with a first offset to generate a second control value; and
a second DAC coupled to the first computing unit for adjusting the second reference level according to the second control value.

### Claim 11 (depends on 8)

The pre-pit signal generating device of claim 8, wherein the reference level generator comprises:
a second computing unit coupled to the decision unit for adjusting the first control value with a second offset to generate a third control value; and
a third DAC coupled to the second computing unit for adjusting a third reference level according to the third control value.

### Claim 12 (depends on 11)

The pre-pit signal generating device of claim 11, further comprising:
a third slicer coupled to the third DAC for generating a second pre-pit signal corresponding to the push-pull signal based on the third reference level.

### Claim 13 (depends on 4)

The pre-pit signal generating device of claim 4, wherein the adjusting device adjusts the gain or the DC level of the push-pull signal according to the detecting result of the duty detector.

### Claim 14 (depends on 13)

The pre-pit signal generating device of claim 13, wherein the adjusting device comprises:
a decision unit coupled to the duty detector for generating a control value according to the detecting result of the duty detector;
a gain amplifier coupled to the first slicer; and
a first digital-to-analog converter (DAC), coupled to and disposed between the decision unit and the gain amplifier, for controlling the gain amplifier to adjust the gain of the push-pull signal according to the control value.

### Claim 15 (depends on 13)

The pre-pit signal generating device of claim 13, wherein the adjusting device comprises:
a decision unit coupled to the duty detector for generating a control value according to the detecting result of the duty detector;
a first digital-to-analog converter (DAC) coupled to the decision unit for generating a DC signal according to the control value;
a resistor unit having a first and a second terminals where the first terminal is coupled to the first DAC and the second terminal is coupled to the first slicer; and
a capacitor unit having a first and a second terminals where the first terminal is coupled to the push-pull signal and the second terminal is coupled to the second terminal of the resistor unit.

### Claim 16 (depends on 13)

The pre-pit signal generating device of claim 13, wherein the second slicer slices an adjusted push-pull signal generated from the adjusting device based on the second reference level to generate the first pre-pit signal.

### Claim 17 (depends on 1)

The pre-pit signal generating device of claim 1, wherein the predetermined ratio is either less than 0.4 or greater than 0.6.

### Claim 18 (depends on 1)

The pre-pit signal generating device of claim 1, wherein the first reference level received by the reference level generator is identical to the first reference level output from the duty ratio controller.

### Claim 19

A detecting device for detecting a header region of an optical storage medium, the detecting device comprising:
a first slicer for generating a first sliced signal corresponding to a push-pull signal and a first reference level, wherein the push-pull signal is retrieved from the optical storage medium;
a first duty ratio controller coupled to receive the first sliced signal for adjusting the first reference level or the push-pull signal to control a duty ratio of the first sliced signal to a first predetermined ratio;
a first reference level generator coupled to the first duty ratio controller for generating a second reference level corresponding to the first reference level;
a second slicer coupled for generating a second sliced signal corresponding to the push-pull signal and a third reference level;
a second duty ratio controller coupled to receive the second sliced signal for adjusting the third reference level or the push-pull signal to control a duty ratio of the second sliced signal to a second predetermined ratio greater than the first predetermined ratio;
a second reference level generator coupled to the second duty ratio controller for generating a fourth reference level corresponding to the third reference level; and
a header region detecting module coupled to receive the second reference level, the fourth reference level, and the push-pull signal for detecting a header region of the push-pull signal according to the second and fourth reference levels.

### Claim 20 (depends on 19)

The detecting device of claim 19, wherein the header region detecting module comprises:
a third slicer coupled to receive the push-pull signal and the second reference level for generating a first detection signal corresponding to the push-pull signal and the second reference level;
a fourth slicer coupled to receive the push-pull signal and the fourth reference level for generating a second detection signal corresponding to the push-pull signal and the fourth reference level; and
a determining unit coupled to the third and fourth slicers for generating a header signal according to the first and second detection signals.

### Claim 21 (depends on 20)

The detecting device of claim 20, wherein the determining unit is an OR gate.

### Claim 22 (depends on 19)

The detecting device of claim 19, wherein the optical storage medium is a DVD-RAM disc.

### Claim 23 (depends on 19)

The detecting device of claim 19, wherein the first predetermined ratio is less than 0.4 and the second predetermined ratio is greater than 0.6.

### Claim 24 (depends on 19)

The detecting device of claim 19, wherein the first duty ratio controller adjusts the gain or the DC level of the push-pull signal coupling to the first slicer to control the duty ratio of the first sliced signal.

### Claim 25 (depends on 19)

The detecting device of claim 19, wherein the second duty ratio controller adjusts the gain or the DC level of the push-pull signal coupling to the second slicer to control the duty ratio of the second sliced signal.

### Claim 26

A detecting device for detecting a header region of an optical storage medium, the detecting device comprising:
a slicer for generating a sliced signal corresponding to a received push-pull signal retrieved from the optical storage medium and a first reference level;
a duty ratio controller coupled to receive the sliced signal for adjusting the first reference level or the push-pull signal to control a duty ratio of the sliced signal to a predetermined ratio;
a reference level generator coupled to receive the first reference level output from the duty ratio controller for generating a second reference level corresponding to the first reference level; and
a header region detecting module coupled to receive the second reference level, the push-pull signal, and a third reference level for detecting a header region of the push-pull signal according to the second reference level and the third reference level, the third reference level corresponding to the second reference level.

### Claim 27 (depends on 26)

The detecting device of claim 26, wherein the duty ratio controller adjusts the gain or the DC level of the push-pull signal coupling to the slicer to control the duty ratio of the sliced signal.

### Claim 28 (depends on 26)

The detecting device of claim 26, further comprising: a computing unit, coupled to the reference level generator and the header region detecting module, for subtracting the second reference level from two times of the maximum amplitude of the push-pull signal to generate the third reference level.

### Claim 29 (depends on 26)

The detecting device of claim 26, wherein the second reference level and the third reference level are symmetrical with respect to the DC level of the push-pull signal.

### Claim 30 (depends on 26)

The detecting device of claim 26, wherein the first reference level received by the reference level generator is identical to the first reference level output from the duty ratio controller.

### Claim 31

A duty ratio control loop comprising:
a slicer for slicing an incoming signal and a reference level to generate a sliced signal; and
a duty ratio controller coupled to receive the sliced signal for adjusting the reference level or the incoming signal to control a duty ratio of the sliced signal to a predetermined ratio, the duty ratio controller comprising:
a duty detector coupled to the slicer for detecting the duty ratio of the sliced signal; and
an adjusting device coupled to the duty detector and the slicer for adjusting the reference level or the incoming signal according to the detecting result of the duty detector, the adjusting device comprising:
a decision unit coupled to the duty detector for generating a control value according to the detecting result of the duty detector;
a gain amplifier coupled to the slicer; and
a digital-to-analog converter (DAC), coupled to and disposed between the decision unit and the gain amplifier, for controlling the gain amplifier to adjust the gain of the incoming signal according to the control value;
wherein the adjusting device adjusts the gain of the incoming signal according to the detecting result of the duty detector.

### Claim 32 (depends on 31)

The duty ratio control loop of claim 31, wherein the duty detector comprises:
a sampling unit for sampling the sliced signal to generate a sampled signal; and
a counter coupled to the sampling unit and the adjusting device for determining the detecting result by counting the sampled signal.

### Claim 33 (depends on 31)

The duty ratio control loop of claim 31, wherein the duty detector comprises:
a low-pass filter for low-pass filtering the sliced signal to generate a filtered signal; and
a comparator coupled to the low-pass filter and the adjusting device for determining the detecting result by comparing the filtered signal with a predetermined value.

### Claim 34 (depends on 31)

The duty ratio control loop of claim 31, wherein the adjusting device is a charge pump or an analog integrator.

### Claim 35 (depends on 31)

The duty ratio control loop of claim 31, wherein the adjusting device comprises:
a decision unit coupled to the duty detector for generating a control value according to the detecting result of the duty detector; and
a digital-to-analog converter (DAC) coupled to the decision unit for adjusting the reference level according to the control value.

### Claim 36 (depends on 35)

The duty ratio control loop of claim 35, wherein the decision unit is a counter or a digital integrator.

### Claim 37 (depends on 31)

The duty ratio control loop of claim 31, wherein the adjusting device adjusts the DC level of the incoming signal according to the detecting result of the duty detector.

### Claim 38 (depends on 37)

The duty ratio control loop of claim 37, wherein the adjusting device further comprises:
a decision unit coupled to the duty detector for generating a control value according to the detecting result of the duty detector;
a digital-to-analog converter (DAC) coupled to the decision unit for generating a DC signal according to the control value;
a resistor unit having a first and a second terminals where the first terminal is coupled to the DAC and the second terminal is coupled to the slicer; and
a capacitor unit having a first and a second terminals where the first terminal is coupled to the incoming signal and the second terminal is coupled to the second terminal of the resistor unit.