KR100553915B1 - Apparatus, Method, and Computer-readable Medium for measuring jitter of sample signal - Google Patents

Abstract

An apparatus for measuring jitter of a sample signal is disclosed. An apparatus for measuring jitter of a sample signal according to the present invention includes: a) a delay unit for generating a delay signal by delaying a sample signal by a time of various multiples of a sampling period; b) a zero crossing extracting unit for extracting a zero crossing point based on a code change of a sample present at a predetermined time with respect to various delay signals generated; c) a parallax movement generating unit for generating a parallax movement at the zero crossing based on the geometric relationship of the samples present at the same time of the delay signal with respect to the extracted zero crossing; And d) a jitter generator for generating jitter values based on the parallax shift. According to the present invention, the accuracy of jitter can be increased.

Description

Apparatus, Method, and Computer-readable Medium for measuring jitter of sample signal

1 shows an optical disk system and a conventional jitter measuring device.

2A and 2B illustrate the digital and analog signals of FIG. 1;

3 is a diagram illustrating an internal configuration of a conventional jitter measuring device.

4 is a view showing a jitter measuring device according to an embodiment of the present invention.

5 is a diagram illustrating a structure of a DC compensator 500.

6 is a view showing in more detail the internal configuration of the delay unit and the parallax movement generating unit.

7 illustrates a first delay signal, an intermediate delay signal, and a second delay signal.

8 is a time flow diagram illustrating a jitter generation method according to the present invention.

TECHNICAL FIELD The present invention relates to a jitter measuring apparatus and method, and more particularly, to a method and apparatus for measuring jitter of a sample signal read out from an optical disc.

In optical disk systems, a method of measuring the jitter characteristic of a signal is widely used as a method of checking the quality of an output signal. The jitter characteristic refers to the phase change of the pulse signal passing through the transmission channel at the original pulse position by external factors. In an optical disc system, the transmission channel refers to all parts through which the signal passes until the high frequency (RF) signal read out from the optical disc passes through the decoder and the final binary signal is detected. Recently, the method of checking the signal quality is becoming more important as the optical disc becomes denser, such as DVD.

1 is a view showing an optical disk system and a conventional jitter measuring device.

The optical disc system 100 includes a signal reading and high frequency (RF) amplifier 110, an analog-to-digital converter 120, a digital signal processor 130, and a digital-to-analog converter 140. The signal readout and high frequency (RF) amplifier 110 reads the high frequency (RF) signal from the optical disk and amplifies the high frequency (RF) signal to a degree suitable for digital processing. The analog-to-digital converter 120 amplifies the amplified high frequency (RF) signal and supplies it to the digital signal processor 130. The digital signal processor 130 generates a binary signal by decoding the received digital signal. The decoding operation includes an error correction process. The digital-analog converter 140 converts the output digital signal into an analog signal and supplies the analog signal to another device that requires the analog signal as an input.

In the conventional jitter measuring method, the jitter measuring apparatus 150 receives an output signal of the digital-analog converter 140 as an input signal. That is, in the conventional method, the signal to be subjected to jitter measurement is an analog signal, the jitter value is measured after converting the output digital signal into an analog signal.

2A and 2B are diagrams illustrating the digital signal 135 and the analog signal 145 of FIG. 1.

In FIG. 2A, the output signal of the digital signal processor 130 is a pulse signal having consecutive samples having a predetermined size at a sampling time T. In theory, if no jitter occurs at all, the interval between each sample will all be constant as the sampling time T.

In FIG. 2B, the output signal of the digital-analog converter 140 is a signal having a continuous value after holding each sample for a sampling time T. In FIG. In the output signal of the ideal digital-analog converter 140, the time intervals of the samples in each section will be constant as the sampling time T.

However, in an actual embodiment, the time interval of each section of the output signal 150 is not constant. This is because the actual digital-to-analog converter includes parasitic capacitance, which generates jitter. The jitter generated at this time depends on the value of parasitic capacitance.

Yet another conventional jitter measurement method includes an analog low band filter (not shown) between the digital-to-analog converter 140 and the jitter measurement device 150 in the configuration of FIG. In this case, the accuracy of the jitter measurement also depends on the nonlinearity of the gain-frequency or phase-frequency of the lowband filter.

The phase-frequency and gain-frequency characteristics of the low-band filter are always nonlinear, as shown in Equation 1 below, which adversely affects the accuracy of jitter measurement.

[Equation 1]

Where K is the gain characteristic, T is the sampling period and f is the frequency of the signal read out from the optical disk.

3 is a diagram illustrating an internal configuration of the jitter measuring device 150.

The conventional jitter measuring device 150 includes an analog-to-digital converter 310, a band pass filter 320, a zero crossing time estimator 330, a period estimator 340, and a jitter detector 350.

The output analog signal 145 of the optical disk system is converted into a digital signal 315 by the analog-digital converter 310. The converted digital signal 315 is filtered by the band pass filter 320 to be converted into a signal 325 containing only components within a constant frequency range around the reference frequency.

The zero crossing time estimator 330 estimates the zero crossing time 335 through data interpolation on the band-passed signal 325. The data interpolation method interpolates data around a zero crossing of waveform data representing a digital signal around a reference frequency, selects waveform data closest to the zero crossing existing between the interpolated waveform data, and tactics the time of the selected waveform data. It is a technique of estimating the time of one zero crossing. Data interpolation includes linear interpolation, quadratic interpolation, Nth degree interpolation, and cubic spline interpolation.

The period estimator 340 detects instantaneous period waveform data of the measurement signal by calculating a time difference value between two estimated zero crossing times.

The jitter detector 350 calculates a cycle-cycle period waveform by calculating a differential waveform for each reference period of the instantaneous period waveform data, and calculates a jitter value using the cycle-cycle period waveform.

However, such a conventional method generates jitter measurement error in a high density optical disk system. Because according to the linear interpolation method used in the conventional method, since the sampling frequency is smaller in the high density optical disk system, the assumption that the signal varies linearly between adjacent clock times is no longer suitable.

In addition, according to the quadratic or Nth order interpolation used in the conventional method, the shape of the signal of the optical disc system is determined by the content recorded on the optical disc and consequently is not suitable to be expressed in quadrature, cubic or similar function. Because of this, the interpolation method also no longer measures accurate jitter values.

Accordingly, an object of the present invention is to provide a jitter measuring apparatus and method for improving the accuracy of jitter characteristics of an optical disk system.

According to another aspect of the present invention, there is provided an apparatus for measuring jitter of a sample signal, the apparatus comprising: a) a delay unit generating a delay signal by delaying a sample signal by a time of various multiples of a sampling period; b) a zero crossing extracting unit for extracting a zero crossing point based on a code change of a sample present at a predetermined time with respect to the generated various delay signals; c) a parallax movement generating unit for generating a parallax movement at the zero crossing point with respect to the extracted zero crossing point based on a geometric relationship of a sample present at the same time of the delay signal; And d) a jitter generator for generating jitter values based on the parallax shift.

The delay unit may include: a1) a first delay unit configured to generate a first delay signal obtained by delaying the sample signal by (N / 2) T; a2) an intermediate delay unit generating an intermediate delay signal delaying the sample signal by ((N / 2) -0.5) T; And a3) a second delay unit for generating a second delay signal that delays the sample signal by ((N / 2) -1) T, where T is a sampling period and N is the number of taps of the delay unit. Indicates.

Here, b) the zero crossing point extraction unit, b1) a first zero crossing point extraction unit for extracting a first zero crossing point based on the first delay signal and the intermediate delay signal; And b1) a second zero crossing point extracting unit configured to extract a second zero crossing point based on the second delay signal and the intermediate delay signal. At this time, each zero crossing point extracting unit extracts the zero crossing point based on the code change of the sample values of the first, middle and second delay signals.

Wherein c) the parallax movement generating unit,

Generate the parallax movement, wherein d _i is a parallax shift at an i-th zero crossing point, U _M is a sample value of the intermediate delay signal at which the zero crossing point is generated, and U _i is the first occurrence of the zero crossing point. The sample value of the first or second delay signal is shown.

에 의해 상기 지터값을 생성하고, 여기서 J는 지터값, k는 상수, d_i 는 시차 이동, M 은 영교차가 발생한 샘플의 수를 나타낸다.In addition, the d) jitter generator, the following equation,

Where j is the jitter value, k is the constant, d _i is the parallax shift, and M is the number of samples with zero crossing.

을 만족하도록 샘플 신호의 DC 성분을 보상하는 DC 보상부를 더 포함하고, 여기서 S(t)는 샘플값의 부호를 나타낸다.In the present invention, the sign of the sample signal is represented by the following equation

Further comprising a DC compensator for compensating for the DC component of the sample signal so as to satisfy, where S (t) represents the sign of the sample value.

In another aspect, the present invention provides a method of measuring jitter of a sample signal, comprising the steps of: a) generating a delay signal for delaying a sample signal by a time of various multiples of a sampling period; b) extracting a zero crossing point with respect to the generated various delay signals based on a code change of a sample present at a predetermined time; c) generating, with respect to the extracted zero crossing point, a parallax shift at the zero crossing point based on a geometric relationship of samples present at the same time of the delay signal; And d) generating a jitter value based on the parallax shift.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 is a view showing a jitter measuring device according to an embodiment of the present invention.

The jitter measuring apparatus 400 of FIG. 4 includes a DC compensator 500 (also referred to as a DC component compensator or a DC component remover), a delay unit 600, a parallax movement generator 700, and a jitter generator 800. Include.

The DC compensator 500 compensates the input signal 502 so as to satisfy the condition for the digital output signal of the optical disk system.

The delay unit 600 generates the first delay signal 612, the intermediate delay signal 622, and the second delay signal 632 by delaying the compensated input signal 602 by various time intervals.

The parallax shift generation unit 700 generates a first time-shift 712 and a first zero-cross point 722 based on the first delay signal 612 and the intermediate delay signal 622. ) Generates a second time-shift 732 and a second zero-cross point 742 based on the second delay signal 632 and the intermediate delay signal 622. do.

The jitter generator 800 generates a final jitter value 832 at the first time-shift 712 and the second time-shift 732.

5 is a diagram illustrating the structure of the DC compensator 500.

The DC compensator 500 receives the input signal 502 to compensate for unnecessary DC components of the digital output signal 502. The input signal 502 is the digital output signal 135 of the digital signal processor 130 of FIG. 1. In addition, the output signal 135 of the digital signal processor 130 must satisfy the following equation (2).

[Equation 2]

Here, S (t) is the output signal 135 of the digital signal processor.

 The DC compensator 500 compensates the input signal 502 to satisfy the above equation. The DC compensator 500 includes a subtractor 510 which subtracts a predetermined DC component from the input signal 502, and a signal selector 520 that converts an output signal of the subtracter 510 into a rectangular form. And a DC component detector 530 which extracts a predetermined DC component satisfying Equation 2 by integrating the output signal of the signal selector.

In FIG. 5, the input signal 502 is converted into a compensated input signal 602 that satisfies Equation 2 through a loop including a subtractor 510, a signal selector 520, and a DC component detector 530. do.

FIG. 6 is a diagram illustrating an internal configuration of the delay unit 600 and the parallax movement generating unit 700 in more detail.

The delay unit 600 generates the first delay signal 612, the intermediate delay signal 622, and the second delay signal 632 by delaying the compensated input signal 602 by various time intervals.

The delay unit 600 includes a first delay unit 610 that delays the input signal 602 by (N / 2) T, and an intermediate delay that delays the input signal 602 by ((N / 2) -0.5) T. The unit 620 includes a second delay unit 610 that delays the input signal 602 by ((N / 2) -1) T. Where N is the number of taps in the filter and T is the sampling period. Each delay unit 610, 620, 630 is implemented with three symmetric FIR filters having a tap number N. This filter should have a cutoff frequency greater than the maximum frequency of the input signal 602. This is to prevent distortion of the original signal.

7 is a diagram illustrating a first delay signal 612, an intermediate delay signal 622, and a second delay signal 632.

In FIG. 7, a dotted line represents a virtual analog signal representing the original signal corresponding to the input signal 602, and each sample represents samples delayed by a predetermined delay in each delay unit 610 to 630. In FIG.

The parallax movement generating unit 700 extracts a first zero-crossing point 722 based on the first delayed signal 612 and the intermediate delayed signal 622. A second zero crossing point extractor 740, a first zero crossing point 722, and a first delay to extract the second zero crossing point 742 based on the second delay signal 632 and the intermediate delay signal 622. A first parallax shift generation unit 710 for generating a first parallax shift 712 based on the signal 612 and the intermediate delay signal 622, and a second zero crossing point 742, a second delay signal 632. And a second parallax movement generator 730 that generates a second parallax movement 732 based on the intermediate delay signal 622.

The first zero crossing extracting unit 720 extracts the first zero crossing point 722 based on the first delay signal 612 and the intermediate delay signal 622, and the second zero crossing extracting unit 740 is the second. The second zero crossing point 742 is extracted based on the delay signal 632 and the intermediate delay signal 622. The first zero crossing point refers to a zero crossing point extracted from the relationship between the first delay signal 612 and the intermediate delay signal 622, and the second zero crossing point refers to a relationship between the second delay signal 632 and the intermediate delay signal 622. Refers to the zero crossing point extracted from

In the intermediate delay signal of FIG. 7, sample AB represents the median value of sample B of the first delay signal and sample A of the second delay signal. Thus, sample AB can be regarded as a new sample existing between sample A and sample B in the virtual analog signal. This property can be used to extract the zero point intersection.

In other words, in Fig. 7, sample AB has the same sign as sample A. This indicates that there is no zero crossing between samples A and AB. However, the signs of samples BC and C are different. Therefore, it can be seen that there is a zero crossing point between Sample BC and Sample C.

Using this principle, first and second zero crossings 722, 742 are extracted.

The first and second parallax movement generators 710 and 730 analyze the first, second and intermediate delay signals 612.632 and 622 to determine the positional difference between the ideal zero crossing point and the actual zero crossing point caused by signal distortion, that is, zero crossing parallax shift. produces a zero cross time shift. The parallax shift of the zero crossing can be generated from the geometric relationship of each delay signal 612, 622, 632.

The sampling frequency is synchronized with the output signal 135 of the optical disc system. Thus, we can assume that the ideal position of the zero crossing in the present invention is the intermediate position of the adjacent sample of the original signal 135. According to this assumption, for example, the time shift d between the samples BC and C can be expressed by Equation 3 according to the geometric relationship of the signal of FIG. 7.

[Equation 3]

Where U _BC is the sample value of sample BC and U _C is the sample value of sample C.

d1 is the parallax shift of the zero crossing which occurred between sample BC and sample C. From FIG. 7, since the zero crossing point between the sample BC and the sample C occurs between the first delay signal and the intermediate delay signal, d1 is the first parallax movement 712 and is generated by the first parallax movement generation unit 710. do. Here sample BC and sample C were selected based on the first zero crossing point 722.

From Fig. 7, it can be seen that the next intersection point appearing after the intersection point by the sample BC and the sample C appears between the sample DE and the sample E. In the same principle as in Equation 3, the time shift of the next intersection point is represented by the following Equation 4. Calculated as

[Equation 4]

Where U _DE is the sample value of the sample DE and U _D is the sample value of the sample D.

d2 is the parallax shift of the zero crossing that occurs between sample D and sample DE. From FIG. 7, since the zero crossing point between the sample D and the sample DE occurs between the second delay signal and the intermediate delay signal, d2 is the second parallax movement 732 and is generated by the second parallax movement generation unit 730. do. Here sample D and sample DE were selected based on the second zero crossing point.

Generalizing Equations 3 and 4 can be summarized as Equation 5 below.

[Equation 5]

Where d _i is a parallax shift at an i-th zero crossing point, U _M is a sample value of the intermediate delay signal at which the zero crossing point occurs, and U _i is a sample value of the first or second delay signal at which the zero crossing point occurs. Indicates.

The jitter generator 800 generates a final jitter value 832 based on the first parallax movement 712 and the second parallax movement 732.

Since the jitter value represents the parallax shift of the sample signal, it can be generated by the following equation (6).

[Equation 6]

Where J is the jitter value, k is the constant, d _i is the first and second parallax shifts, and M is the number of samples with zero crossings. The constant k can be selected from several values to get the output you want as a result of jitter calculations. For example, if an indicator is used to alert the user when a jitter value is output above the permissible value, the user may automatically recognize the appearance of unwanted jitter by adjusting the k value to a value suitable for the indicator's operational output. Can be.

8 is a time flow diagram illustrating a jitter generation method according to the present invention.

In step 810, the DC component of the signal 602 to be measured is compensated for. Compensation of the DC component is generated by removing a predetermined DC value from the measurement signal, generating a predetermined DC value based on Equation 2, and adding it back to the measurement signal again.

In operation 820, first and second delay signals and an intermediate delay signal are generated by delaying the measurement signal by several hours associated with a sampling period.

In step 830, by analyzing the first delay signal and the intermediate delay signal for a predetermined time, the first zero crossing point existing between the first delay signal and the intermediate delay signal is extracted, and the second delay for another predetermined time. By analyzing the signal and the intermediate delay signal, a second zero crossing point existing between the second delay signal and the intermediate delay signal is extracted. In Fig. 7, the signs of samples B, C and BC are extracted at time t2, and according to the change of these signs, it can be seen that a zero crossing occurs between sample BC and sample C, and at time t4, samples D, E And the sign of DE is extracted, and it can be seen that a zero crossing occurs between sample D and DE according to the change of these signs.

In step 840, a parallax shift of the sample at the extracted zero intersection point is generated. Based on the first zero crossing point, a parallax shift is generated between the first delay signal and the intermediate delay signal, and based on the second zero crossing point, a parallax shift between the second delay signal and the intermediate delay signal is generated.

The parallax shift can be generated from the geometric relationship between the sample value (average value) at the ideal zero crossing point and the actual sample value.

In FIG. 7, the parallax shift between samples BC and C, i.e., d1 in Equation 3 is the parallax shift between the first delay signal and the intermediate delay signal, and the parallax shift between samples D and DE, i.e. This is the parallax shift between the delay signal and the intermediate delay signal.

In step 850, the jitter value is generated based on the generated parallax movement. In one embodiment of the invention, the jitter value is expressed as

On the other hand, the jitter generation method according to the present invention can be created by a computer program. Codes and code segments constituting the program can be easily inferred by a computer programmer in the art. The program is also stored in a computer readable media, and read and executed by a computer to implement jitter value generation. The information storage medium includes a magnetic recording medium, an optical recording medium, and a carrier wave medium.

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the appended claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

According to the present invention, by generating the jitter characteristic from the geometric relationship of the sample of the measurement signal, it is possible to generate the jitter value with further increased accuracy.

Claims (20)

In the jitter measuring device of the sample signal, a) a delay unit for generating a delay signal by delaying the sample signal by a time of various multiples of the sampling period; b) a zero crossing extracting unit for extracting a zero crossing point based on a code change of a sample present at a predetermined time with respect to the generated various delay signals; c) a parallax movement generating unit for generating a parallax movement at the zero crossing point with respect to the extracted zero crossing point based on a geometric relationship of a sample present at the same time of the delay signal; And d) a jitter generator for generating a jitter value based on the parallax shift. The method of claim 1, wherein the a) delay unit, a1) a first delay unit configured to generate a first delayed signal delaying the sample signal by (N / 2) T; a2) an intermediate delay unit generating an intermediate delay signal delaying the sample signal by ((N / 2) -0.5) T; And a3) a second delay unit for generating a second delay signal delaying the sample signal by ((N / 2) -1) T, where T is a sampling period and N is a tap number of a delay unit; Device characterized in that it represents. The method of claim 2, wherein b) the zero crossing point extraction unit, b1) a first zero crossing point extraction unit configured to extract a first zero crossing point based on the first delay signal and the intermediate delay signal; And b2) a second zero crossing point extracting unit configured to extract a second zero crossing point based on the second delay signal and the intermediate delay signal. The method of claim 3, wherein b1) The first zero crossing point extraction unit extracts the first zero crossing point based on a code change of a sample of the first delay signal and the intermediate delay signal present at a predetermined time, b2) A second zero crossing point extraction unit extracts the second zero crossing point based on a code change of a sample of the second delay signal and the intermediate delay signal existing at a predetermined time. The method of claim 3, wherein the c) parallax movement generating unit, And generating the parallax shift based on the average value of the first delay signal and the second delay signal at a predetermined time present at the zero crossing point and the sample value of the intermediate delay signal. The method of claim 5, wherein the c) parallax movement generating unit,

Generate the parallax movement, wherein d _i is a parallax shift at an i-th zero crossing point, U _M is a sample value of the intermediate delay signal at which the zero crossing point is generated, and U _i is the first occurrence of the zero crossing point. And a sample value of the first or second delay signal. The method of claim 6, wherein the c) parallax movement generating unit, c1) a first parallax movement generating unit generating a first parallax movement generated at the first zero crossing point based on the first delay signal, the intermediate delay signal, and the first zero crossing point; And c2) a second parallax movement generating unit for generating a second parallax movement generated at the second zero crossing point based on the second delay signal, the intermediate delay signal, and the second zero crossing point. The apparatus of claim 1, wherein the d) jitter generator generates the jitter value by a function of increasing the jitter value as the value of the parallax shift increases. The jitter generator of claim 8, wherein

Generate the jitter value, wherein J is the jitter value, k is a constant, d _i is the parallax shift, and M is the number of samples with zero crossing. The method of claim 1, wherein the sign of the sample signal is

And a DC compensator for compensating for the DC component of the sample signal so as to satisfy?, Wherein S (t) represents the sample signal. In the jitter measurement method of a sample signal, a) generating a delay signal that delays the sample signal by a time of various multiples of the sampling period; b) extracting a zero crossing point with respect to the generated various delay signals based on a code change of a sample present at a predetermined time; c) generating, with respect to the extracted zero crossing point, a parallax shift at the zero crossing point based on a geometric relationship of samples present at the same time of the delay signal; And d) generating a jitter value based on the parallax shift. The method of claim 11, wherein step a) comprises: a1) generating a first delayed signal delaying the sample signal by (N / 2) T; a2) generating an intermediate delay signal which delays the sample signal by ((N / 2) -0.5) T; And a3) generating a second delayed signal that delays the sample signal by ((N / 2) -1) T, where T denotes the sampling period and N denotes the number of taps of the delayer; How to feature. The method of claim 12, wherein b), b1) extracting a first zero crossing point based on the first delay signal and the intermediate delay signal; And b2) extracting a second zero crossing point based on the second delay signal and the intermediate delay signal. The method of claim 13, wherein the step b1) is performed based on code changes of samples of the first delay signal and the intermediate delay signal present at a predetermined time, and the step b2) is present at a predetermined time. And performing a code change of samples of the second delay signal and the intermediate delay signal. The method of claim 13, wherein step c) And performing an average value of the first delay signal and the second delay signal at a predetermined time present at the zero crossing point, and a sample value of the intermediate delay signal. The method of claim 15, wherein the step c) is

D _i is the parallax shift at the i-th zero crossing point, U _M is the sample value of the intermediate delay signal at which the zero crossing point occurs, and U _i is the first or second occurrence of the zero crossing point. And a sample value of the delay signal. 12. The method of claim 11, wherein step d) is performed by a function of increasing the jitter value as the value of the parallax shift increases. The method of claim 17, wherein the d) is,

Wherein J is the jitter value, k is the constant, d _i is the parallax shift, and M is the number of samples with zero crossing. The method of claim 11, wherein the sign of the sample signal is

And a DC compensating step of compensating the DC component of the sample signal so as to satisfy the following formula, wherein S (t) represents the sample signal. A computer-readable recording medium having recorded thereon a program for executing the method of claim 11 on a computer.

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