JPS60185260A - Digital signal recording system - Google Patents

Abstract

PURPOSE:To attain synchronization detection resistive to a bit slip by arranging a buffer part in the front or back of a dispersedly inserted synchronizing signal, allowing the width of a detecting window for the synchronizing signal to be expanded when synchronization detection is applied to the read-out data. CONSTITUTION:Plural sectors are arrayed in series on an optical disc, data are recorded in respective sectors and the front and back of each sector are divided by gaps 21. A preamble 20a for leading bit synchronization, sector synchronization 20b, buffer part 20g, sector address 20c, and a gap 20d are successively formed in a sector following the gap 21, then a data part is recorded. Since the sector synchronization 20b is formed as a pattern having sharp self-correlation and the preamble 20a is constituted of simply repeated patterns having minimum inversion intervals, a detecting window can be expanded to the front of the synchronization 20b. The detecting window can be expanded also to the buffer part 20g arranged on the back of the sector synchronization 20b. Thus, synchronization detection resistive to a bit slip can be attained and stable signal reproducing can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a digital signal recording method for a disk memory used in a digital data transmission system, and in particular to an optical disk and a floppy disk.

The present invention relates to a digital signal recording method that makes it possible to detect a synchronization signal inserted into a digital signal recorded on a recording medium such as a hard disk under optimal conditions.

In conventional digital signal systems, in the case of a synchronization method that uses a pattern with sharp autocorrelation as a synchronization signal, the maximum allowable detection window width is uniquely determined by the autocorrelation function of the synchronization signal pattern, and detection Increasing the window width may cause false synchronization.

However, depending on the signal system, the jitter of the transmission signal is large and it may be necessary to further widen the detection window width in cases where the jitter is large and the signal is disturbed by noise in the transmission path. Furthermore, in any case, setting the detection window width as large as permissible has the advantage that synchronization is easier to pull in, and that once synchronization is established, it is difficult to lose synchronization.

Purpose The present invention has been made in view of the above points, and it is an object of the present invention to provide a recording method for digital signals on a recording medium that makes it possible to expand the detection window width without deteriorating synchronization performance. In particular, even when a pattern with sharp autocorrelation is used as a synchronization signal, it is possible to set an optimal detection window width that is larger than the detection window width uniquely determined by such a pattern. This provides a digital signal recording method for

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows an optical disk system to which the present invention can be applied.

As shown, an optical disc 1 as a recording medium is rotatably provided, and a drive motor 3 is driven in response to a drive signal from a system controller 2 to rotate the optical disc 1. As will be described later, in this embodiment, information is recorded on the optical disc 1 in a spiral manner. The system controller 2 is connected to a linear motor 5 provided integrally with the optical pickup 4, and controls the linear motor 5 to control the radial position of the optical pickup 4 with respect to the optical disk 1. The optical pickup 4 irradiates the optical disc 1 and receives reflected light 4a from the optical disc 1 to perform tracking, focusing, etc. on the optical disc 1.
In addition to performing relative position control on the optical disc 1,
Read the information recorded in the .

Data collected from the reflected light received by the optical pickup 4 is sent to the arithmetic circuit 6. On the other hand, an optical pickup servo system 7 is provided, which controls the relative position of the optical pickup with respect to the optical disk 1 in response to respective signals from the arithmetic circuit 6 and the system controller 2. Data from the arithmetic circuit 6 is supplied to the signal detection processing circuit 8,
The required signal detection takes place. Moreover, the signal detection processing circuit 8
are connected to supply signals to the sector detection circuit 9, frame synchronization detection circuit 10, and demodulation circuit 11, respectively. or,
Sector detection circuit 9 is connected to system controller 2, while frame synchronization detection 10 and demodulation circuit 11 is connected to error correction decoding circuit 12.

Further, an automatic light amount adjustment circuit 13 for adjusting the amount of light in the optical pickup 4 is provided, and a modulation circuit 14, a frame synchronization generation circuit 15, and an error correction code circuit 16 are also connected as shown. Further, it is connected to a host device (not shown) such as a computer or the like via a system controller 2, an error correction decoding circuit 12, an error correction code circuit 16, and an interface 17, which perform overall control of the optical disk system.

Sector-type data formats 1 to 1 of the optical disk 1 conventionally used in the optical disk system of FIG. 1 are shown in FIGS. 2(a) to 2(C). As shown in FIG. 2(a), a plurality of sectors 20 are arranged in series and recorded in a spiral shape on the optical disk 1, and each sector 2
The area before and after 0 is separated by a gap 21. Figure 2 (b
) As shown in FIG.
0c, a gap 20d at the boundary between the synchronization section and the data section, a preamble 20e, and n frames 2Of. Furthermore, as shown in FIG. 2(C), each frame 2Of
is composed of a frame synchronization 20f1 and a data section 20t2.

When reading data recorded on the optical disk 1 having the data format shown in FIG. 2(a) to <O), the sector detection circuit 9 detects the sector synchronization 20b, The positions of the preamble 20e, frame synchronization 20f1, and frame data section 20f2 are determined from the positions, and data is read.

Therefore, it is impossible to read data accurately unless the position of the sector synchronization signal 20i1 is accurately determined.

An example of a detection circuit for detecting such a sector synchronization signal 20b is shown in FIG. In the circuit shown in FIG. 3, a bit synchronization detector 30 receives data supplied from the signal detection processing circuit 8, and a bit synchronization detector 30 determines whether or not the data input from the bit synchronization detector 30 matches a predetermined synchronization signal. A matched filter 31 that outputs a matching value such as a correlation value for a signal;
Beep] - Clock CLK output from the synchronization detector 30
A prediction function generation circuit 32 receives input and outputs a prediction function related to synchronization signal generation, and outputs a matching value (matching bit number) from a matched filter. ll! An adder 33 that adds to the prediction function from the I-function generating circuit 32 and an added value output from the adder 33 are compared with a predetermined threshold value, and if the value exceeds the threshold value, a sector synchronization detection pulse is output. It has a comparator 34 that performs. Therefore, when detecting the sector synchronization signal 20b using the detection circuit shown in FIG. While outputting the matching value representing the previously detected sector synchronization position @40 (see Figure 4), the matching value is set before and after the next expected expected synchronization position (this width before and after is called the detection window width). The comparator 34 detects a point at which the level is equal to or higher than the reference level, and determines it as the current synchronization position. This state is shown in FIG. In FIG. 4, WO indicates the most probable position for sector synchronization, and Wl indicates the detection window width.

In this case, the allowable maximum detection window width that can be set is uniquely determined by the autocorrelation function of the synchronization signal pattern. Outside this uniquely determined maximum allowable detection window,
The matching value from the matched filter 31 may exceed the set reference level, and therefore, if the detection window is set larger than the maximum allowable width, there is a risk of false synchronization. On the other hand, if the signal has large jitter due to effects during transmission, the amount of variation may not be within the maximum allowable range due to the expansion and contraction of the detection time between two adjacent sector synchronizations. . In order to deal with such a situation, it is necessary to expand the detection window without causing false synchronization.

FIG. 5 shows a data format when information is written on the optical disc 1 based on one embodiment of the present invention. FIG. 5 corresponds to FIG. 2 (13), and the same elements are given the same reference numbers.

In the configuration shown in FIG. 5, a buffer section 20Q is provided between the sector synchronization 20b and the sector address 200.

As mentioned above, the preamble 20a provided before the sector synchronization 20b is for acquiring bit synchronization, and has a minimum inversion interval of 11! Consists of repetitive signals.

Here, between the sector synchronization 20b of two adjacent sectors 20.20 and the next sector synchronization 20b, that is, the sector capacity is 2,000 bits, and the system jitter is ±0.
In the case of 1%, the distance between sector sync and sector sync is 20,0OOX 01001=20, so ±2
It may fluctuate around 0 bit.

In this case, when attempting to detect the next sector synchronization based on one sector synchronization 20b, the detection window width must be at least ±20 pips from the expected position. on the other hand,
If the maximum allowable detection window width determined from the autocorrelation function of the sector synchronization pattern is 5 bits at the expected position, then
Unless the detection window is further expanded outward by 15 bits, sector synchronization detection may not be performed.

Here, if the preamble 20a provided before the sector synchronization 20b is composed of a simple repeating pattern, the correlation value with the sector synchronization pattern is known in advance, so the preamble 20a provided before the sector synchronization 20b is Preamble detection window 2
0 side, that is, in front of the sector synchronization 20b, it is easy to set the level so that the output of the matched filter 31 does not exceed the reference level. It is possible to expand the detection window forward. Furthermore, in the configuration shown in FIG.
The pattern with a small correlation with the sector synchronization pattern is stored in the buffer section 2.
Since it is provided after the sector synchronization 20b as 00,
It is possible to extend the detection window to the rear of the sector synchronization 20b. Under the above conditions, a buffer of 15 bits or more may be provided.

Note that in a system with relatively little jitter, if the enlarged portion from the maximum detection window width determined from the synchronization signal pattern is relatively small, the length of the buffer section 20Q can be shortened, so it is possible to use a system with bit synchronization components. At least no particular problem will occur. Therefore, in such a case, the buffer section 20! +
It is possible to form a non-modulated region (DC signal) of about several pils. Note that this also applies when the sector interval is relatively short.

On the other hand, when the jitter in the system is relatively large and a considerably large detection window width is required, the buffer section 20
It is necessary to form g relatively long. In this case, it is necessary to configure the buffer section 20Q with a self-clockable signal, otherwise there is a risk of bit synchronization being lost. Therefore, in this case, the buffer section 20 (+) is configured with the same signal as the signal necessary to form the preamble 20a, that is, a repetitive signal with a minimum inversion interval.Furthermore, a repetitive signal with a minimum inversion interval is used. Alternatively, it is also possible to configure the buffer section 20g using a repetitive signal with an inversion interval that matches the modulation rule and a pattern that is less consistent with the sector synchronization pattern.

Effects As explained in detail above, according to the present invention, even when a sharp autocorrelation pattern is used as a synchronization signal, false synchronization is less likely to occur, and the detection window can be set larger than in the conventional technology. Therefore, strong synchronization detection for bit strips becomes possible, and stable signal reproduction becomes possible.

Although specific embodiments of the present invention have been described in detail above, the present invention should not be limited to these specific embodiments, and many modifications may be made without departing from the technical scope of the present invention. Of course, modifications are possible.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an optical disc system to which the present invention can be applied, FIGS. 3 is a block diagram showing an example of the configuration of the sector synchronization detector used in the system of FIG. 1, FIG. 4 is an explanatory diagram useful for explaining the operation of the configuration of FIG. 3, and FIG. 5 FIG. 2 is an explanatory diagram showing a data format in one embodiment of the present invention. (Explanation of symbols) 20: Sector 21: Gap 20b = Sector synchronization 20Q: tfl'ej section patent applicant Rico Co., Ltd. -

Claims (1)

[Claims] 1. When recording a digital signal series in which a synchronization signal is discretely inserted into a recording medium, a buffer section is provided before or after the synchronization signal. A digital signal recording method characterized by making it possible to widen the detection window width of the synchronization signal when performing synchronization detection from data. 2. In claim 1, the synchronization signal has an autocorrelation The recording method is a sector recording method, and each sector has at least a gap separating the sectors, a preamble for human synchronization pull-in, and a preamble for accurately reproducing data. A digital signal recording method characterized by having, in chronological order, a sector synchronization signal and a buffer section for widening a detection window when detecting the sector synchronization signal.