JPH03278376A - Jitter generating method and asymmetry generating method by delay element - Google Patents

Abstract

PURPOSE:To generate a lengthwise symmetric EFM signal to be measured in digital fashion by employing such constitution that prescribed quantity of jitter can be outputted by selecting delay before and behind for the reference delay of a delay element only a specific signal is inputted. CONSTITUTION:When an EFM signal is inputted from an EFM signal generator 21 to a delay 20, a jitter control unit 24 senses only the 3T of the EFM signal, and a command to operate a selector 22 only for prescribed time before and behind the end of a 3T signal is sent out, and a tap except for B is selected by the selector 22. At this time, when the taps A and C are selected, the 3T signal is shortened by, for example, 10ns if it is the tap A, and it is extended by 10ns if it is the tap C, which means that the signal is changed by + or -10ns from a reference 3T signal, and the constant quantity of jitter of 20ns before and behind is generated. In such a manner, it is possible to generate the lengthwise symmetric jitter of constant quantity only for the 3T of the EFM signal including 3T-11T in the digital fashion.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a jitter generation method and an asymmetry generation method for calibrating and evaluating a compact disk (CD) jitter measuring device, and relates to a digital jitter generation method using a delay element. This article concerns how to generate jitter and asymmetry.

[Conventional technology]

EFM and EFM-R used in compact discs
The jitter of the F modulation signal is measured by extracting the 3T wave component with the minimum pulse width from the EFM signal and measuring its fluctuation.

In order to calibrate and evaluate such a jitter measurement device, it is necessary to use an FM signal generator as a 3T wave signal generation source.
It is conceivable to generate a quantitative jitter of the wave, or to use a signal generator for a CD player.

[Problem to be solved by the invention]

An actual EFM signal is composed of composite waves from 3T to ILT. However, unlike an actual EFM signal, the EFM signal generator can only generate jitter of 3T waves, and the generated 3T waves are asymmetrical in time W. Further, there is a problem that the signal generator for CD players cannot be used because the jitter generated is completely uncertain.

Therefore, in order to obtain a measured EFM signal containing quantitative jitter of the 3T wave for appropriately calibrating and evaluating a jitter measuring device, the present invention does not generate the 3T wave using the conventional FM modulation method. By means of using a delay element as a jitter generating device, quantitative jitter is generated in 3T to 11T1 or a specific signal for an EFM signal containing 3T to 11T, and thus a symmetrical EF to be measured is generated.
It is an object of the present invention to provide a jitter generation method in which an M signal is generated digitally.

[Means for Solving the Problems] The above problem is solved by the delay element standard of the present invention only when 3 signals among 3T to 11T EFM signals are input with respect to the input jitter amount and jitter frequency. A jitter generation method using a delay element, characterized in that a predetermined amount of jitter is output by selecting a delay before and after the delay, and a jitter generation method using a delay element, which is characterized in that a predetermined amount of jitter is output by selecting a delay before and after the delay, This is achieved by an asymmetry generation method using a delay element, characterized in that a predetermined asymmetry is output by selecting a rising or falling edge that is earlier or later than the reference delay by a predetermined amount of asymmetry input to the reference delay. Ru.

[Function] Compact disc jitter refers to the fact that when a player reads the bits recorded on the disc, the length of the bits read changes due to the effects of the player's mechanical system, control system, and optical system. This is the occurrence of frequency fluctuation components in the signal. The amount of change in bit length (the amount of jitter) is expressed by time, and the speed of change is expressed by jitter frequency. The amount of jitter is obtained by a jitter input, and the jitter frequency is obtained by a jitter frequency generator. Then, with respect to the input jitter amount and jitter frequency, only when 3 signals among the 3T to 11T EFM signals are input, the delays before and after the standard delay of the delay element are selected. Quantitative jitter is output.

According to the present invention, in order to obtain an EFM signal to be measured containing quantitative jitter of 3T waves for appropriately calibrating and evaluating a jitter measurement device, instead of generating only 3T waves using the conventional FM modulation method, By using a delay element as a jitter generating device, fixed jitter is generated in only three of the EFM signals including 3T to 11T, and thus it is possible to digitally generate a symmetrical EFM signal to be measured. .

The invention can also be applied to the generation of asymmetry, by changing the duty of the pulse by selecting a delay of the rising (or falling) edge earlier or later than the standard to change the duty of the pulse. , asymmetry can be digitally generated in the EFM signal.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram of a jitter generating device according to the present invention. FIGS. 2(a) and 2(b) are diagrams for explaining a jitter generation method using the jitter generation device shown in FIG. 1. FIG. 3 is a schematic diagram of the asymmetry generating device according to the present invention. FIG. 4 is a diagram for explaining an asymmetry generation method using the asymmetry generation device shown in FIG. 3. FIG.

In Figure 1, 20 is a delay, and the total delay is 2
00ns (1 step Ions, total 20 steps)
A C-MOS delay having a delay line is used. 21 is an EFM signal generator, which inputs an EFM signal to the delay 20 and jitter control unit 24.

A selector 22 selects a delay terminal according to a command from the jitter control unit 24 in response to an EFM signal input manually to the delay 20, and outputs a predetermined jittered EFM signal. 23 is a jitter frequency generator. 24 is an EF select signal sent to the selector 22.
This jitter control unit generates an EFM signal input from the M signal generator 2, a jitter input 25, and a jitter frequency input from the jitter frequency generator 23, and controls the selector 22.

In such a jitter generator, the EFM signal from the EFM signal generator 21 is input to the delay line of the delay 20.

Jitter input 25 or jitter frequency generator 23
If either signal is zero, no jitter is output. Figure 2 (a) is based on such O jitter.
The output is output from the 10th tap with a delay of 100 ns as shown in FIG. 2, and the taps are not switched. In this case, the signal is simply delayed by 100 ns.

Next, a case where a jitter of, for example, 20 ns is generated will be explained with reference to FIG. 2(b). Jitter can be generated by inputting a predetermined jitter amount and jitter frequency from the jitter input 25 and the jitter frequency generator 23 to the jitter control unit 24, but the EFM signal input from the EFM signal generator 21 to the delay 20 is 4T. When the signal is ~11T and until the 3T signal is input, the selector 22 remains set to tap B (loons tap) by finger 6 of the jitter control unit 24, and the signal is 10 as in the case of 0 jitter 1 reference.
There is only a delay of 0 ns. And EFM signal generator 2
1 to the delay 20, the jitter control unit 24 senses only 3T of this EFM signal and sends a command to operate the selector 22 only for 230 ns before and after the end of the 3T signal. Taps other than B can be selected at . At this time, A
If you select tap and C, the 3T signal will be 10ns shorter if it is an A tap, and Ions longer if it is a C tap, which means that it has changed by ±10ns from the standard 3T signal, and a fixed jitter of 20ns between the front and rear needles will occur. . In this way, a predetermined jitter can be generated digitally. The jitter thus obtained is 3T selected from 3T to 11T of the EFM signal, and unlike the FM signal, it is symmetrical.

As an application example of the present invention, an asymmetry generation method using a delay element will be described.

FIG. 3 is a schematic diagram of the asymmetry generating device. 30 is a delay, which is composed of a delay line or a delay element for generating asymmetry.

31 is an EFM signal generator that outputs an EFMFM signal to the delay 30 and the asymmetry control unit 34. 32 is a selector for selecting a delay terminal necessary for generating asymmetry. 34 is an asymmetry control unit for operating the selector 32 to generate asymmetry.

35 is an asymmetry input for inputting the amount of asymmetry.

This asymmetry is generated in the same way as the jitter generation method described above, but the difference is that in the case of jitter generation, delays before and after the standard delay are selected, without changing the asymmetry. This is due to the occurrence of jitter. In the case of asymmetry, by changing the duty of the pulse, the EFM is Asymmetry can be generated digitally in the signal.

The jitter generating device and the asymmetry generating device according to the present invention are based on the same principle as described above, but in concrete implementation, both devices can be used in a single device. It can be built into a cascade, or peripheral circuits of the same device can be switched and used.

[Effect of the Invention J As explained above, according to the present invention, in order to obtain a measured EFM signal including quantitative jitter of the 3T wave for appropriately calibrating and evaluating jitter measurement snowmaking, the conventional FM
Instead of generating only 3T waves using a modulation method, 3T-L is generated by using a delay as a jitter generator.
It is possible to digitally generate symmetrical quantitative jitter only in 3T of the EFM signal including IT.

Further, by adding asymmetry to the EFM signal to be measured, it is possible to obtain a jitter generation method that allows accurate jitter measurement under the influence of this asymmetry.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a jitter generating device according to the present invention. FIGS. 2(a) and 2(b) are diagrams for explaining a jitter generation method using the jitter generation device shown in FIG. 1. FIG. 3 is a schematic diagram of the asymmetry generating device according to the present invention. FIG. 4 is a diagram for explaining an asymmetry generation method using the asymmetry generation device shown in FIG. 3. FIG. 20...Delay, 21...EFM signal generator 22
... Selector, 23... Jitter frequency generator, 24... Jitter control unit, 25...
・Jitter input, 30...Delay, 31...
・EFM signal generator, 32...Selector, 34...
・Asymmetric control unit, 35...Asymmetric input

Claims (2)

[Claims] (1) For the input jitter amount and jitter frequency, when an EFM signal of 3T to 11T or a specific signal among them is input, the delay before and after the reference delay of the delay element is selected, so that a predetermined value is determined. A jitter generation method using a delay element, characterized in that a fixed amount of jitter is outputted. (2) For the input EFM signal, a predetermined asymmetry can be achieved by selecting a delay of a rising or falling edge that is earlier or later than the reference delay by a predetermined amount of asymmetry that is input with respect to the reference delay of the delay element. A method for generating asymmetry using a delay element, characterized in that an asymmetry is generated by a delay element.