JPH081737B2 - Digital signal recording system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a digital signal recording method for a disc memory used in a digital data transmission system, and more particularly, it is inserted into a digital signal recorded on a recording medium such as an optical disc, a floppy disc, a hard disc. The present invention relates to a digital signal recording method that enables the detection of a synchronizing signal that is present under optimum conditions.

In the prior art digital signal system, in the case of a synchronization method in which a pattern with a sharp autocorrelation is used as the synchronization signal, the maximum allowable detection window width is uniquely determined by the autocorrelation function of the pattern of the synchronization signal 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 increase the detection window width in the case where the signal is disturbed by noise in the transmission path. In any case, if the detection window width is set to be as large as possible, there is an advantage that the synchronization pull-in becomes easier and the synchronization once obtained is less likely to be lost.

The present invention has been made in view of the above points, and an object of the present invention is to provide a method of recording a digital signal on a recording medium that enables highly accurate sector synchronization. In particular, even when a pattern with sharp autocorrelation is used as the synchronization signal,
It is intended to provide a digital signal recording method capable of setting an optimum detection window width larger than a detection window width uniquely determined by such a pattern.

Configuration 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 in the figure, 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. still,
As will be described later, in this embodiment, information is spirally recorded on the optical disc 1. 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 disc 1. The optical pickup 4 irradiates the optical disc 1 and receives the reflected light 4a from the optical disc 1 to control the relative position of the optical disc 1 such as tracking and focusing and read the information recorded on the optical disc 1.

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 and controls the relative position of the optical pickup with respect to the optical disc 1 in response to signals from the arithmetic circuit 6 and the system controller 2. The data from the arithmetic circuit 6 is supplied to the signal detection processing circuit 8 to perform the required signal detection. The signal detection processing circuit 8 is connected to the sector detection circuit 9, the frame synchronization detection circuit 10, and the demodulation circuit 11 to supply signals. or,
The sector detection circuit 9 is connected to the system controller 2, while the frame synchronization detection 10 and the demodulation circuit 11 are connected to the error correction decoding circuit 12.

Furthermore, an automatic light amount adjusting circuit 13 for adjusting the light amount in the optical pickup 4 is provided, and a modulation circuit 14, a frame synchronization generating 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 via a system controller 2 for performing overall control of the optical disc system, an error correction decoding circuit 12, an error correction coding circuit 16 and an interface 17.

The sector type data format of the optical disc 1 conventionally used in the optical disc system of FIG. 1 is 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 on the optical disk 1 in a spiral shape, and the front and rear of each sector 20 are separated by a gap 21. As shown in FIG. 2B, the sector 20 following the gap 21 for sector division
Has another sector synchronization 20b of the preamble 20a for performing bit synchronization pull-in, a sector address 20c, a gap 20d at the boundary between the synchronization part and the data part, a preamble 20e and n frames 20f. Furthermore, as shown in FIG. 2 (c), each frame 20f frame synchronization 20f ₁ and data section 2
It consists of 0f ₂ .

When reading the data recorded from the optical disc 1 having the data format as shown in FIGS. 2A to 2C, the sector detection circuit 9 performs the synchronization detection of the sector synchronization 20b, and the detection thereof is performed. The positions of the preamble 20e, the frame synchronization 20f ₁ and the frame data portion 20f ₂ are calculated from the position and the data is read. Therefore, it is impossible to accurately read the data unless the position of the sector synchronization signal 20b is accurately determined.

An example of a detection circuit for detecting such a sector synchronization signal 20b is shown in FIG. In the circuit of FIG. 3, the bit synchronization detector 30 to which the data supplied from the signal detection processing circuit 8 is input, and the matching state between the data input from the bit synchronization detector 30 and a predetermined synchronization signal are discriminated. From a matched filter 31 that outputs a matched value as a correlation value for a signal, a predictive function generation circuit 32 that inputs a clock CLK output from the bit synchronization detector 30 and outputs a predictive function related to synchronous signal generation, and a matched filter Of the match value (the number of matching bits) of the adder 33 that adds the match value to the predictive function from the predictive function generating circuit 32, and the added value output from the adder 33 is compared with a predetermined threshold value and exceeds the threshold value. And a comparator 34 that outputs a sector synchronization detection pulse. Therefore, when the sector sync signal 20b is detected using the detection circuit of FIG. 3, the matching filter 31 determines the matching state between the correct sync signal pattern and the incoming data to determine the number of matching bits of both patterns. While outputting the matching value represented, the matching value is set as a reference value before and after the expected predicted sync position from the previously detected sector sync position 40 (see FIG. 4) (this front-back width is called the detection window width). The point at which the level is higher than or equal to the level is detected by the comparator 34, and the current synchronization position is determined. This state is shown in FIG. still,
In FIG. 4, W ₀ indicates the most probable predicted position for sector synchronization, and W ₁ indicates the detection window width.

In this case, the maximum allowable detection window width that can be set is uniquely determined by the autocorrelation function of the pattern of the synchronization signal. Outside the uniquely determined maximum allowable detection window, the matching value from the matched filter 31 may exceed the set reference level. Therefore, setting the detection window larger than the maximum allowable width may cause false synchronization. There is. On the other hand, if the signal has large jitter due to the influence during transmission, 2
Due to the expansion and contraction of the detection time between the adjacent sector synchronizations, the variation amount may not be within the allowable maximum width. 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 for writing information on the optical disc 1 according to one embodiment of the present invention.
FIG. 5 corresponds to FIG. 2 (b), and the same reference numerals are given to the same elements. In the configuration of FIG.
Buffer part 20g between sector synchronization 20b and sector address 20c
Is provided. As described above, the preamble 20a provided before the sector synchronization 20b is for taking in bit synchronization, and is composed of a simple repetitive signal with a minimum inversion interval.

Here, the sector synchronization 20b of two adjacent sectors 20, 20
And the next sector synchronization 20b, that is, when the sector capacity is 2,000 bits and the system jitter is ± 0.1%, the distance between the sector synchronization is 20,000 × 0.001 = 20. It can fluctuate around 20 bits. In this case, if one sector synchronization 20b is used as a reference to detect the next sector synchronization, the detection window width requires at least the expected position ± 20 bits. On the other hand, if the maximum allowable detection window width determined from the autocorrelation function of the sector synchronization pattern is the expected position ± 5 bits, the sector synchronization detection will not be performed unless the detection window is expanded further by 15 bits. There are cases.

Here, when the preamble 20a provided before the sector synchronization 20b is composed of a simple repetitive pattern, the correlation value with the sector synchronization pattern is known in advance, so detection for sector synchronization detection is performed. Window preamble 20
Side, that is, even if it is expanded to the 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, and therefore the sector synchronization 20b of the It is possible to extend the detection window forward. Further, in the configuration of FIG. 5, since a pattern having a small correlation with the sector synchronization pattern is provided behind the sector synchronization 20b as the buffer unit 20g, the sector synchronization 20b
It is possible to extend the detection window to the rear of. Under the above-mentioned conditions, a buffer unit of 15 bits or more may be provided.

It should be noted that, in a system with a relatively small amount of jitter, if the expanded portion from the maximum detection window width determined from the sync signal pattern is relatively small, the length of the buffer section 20g can be short, so there is a bit sync component. Even if it does not occur, no particular problem occurs. Therefore, in such a case, the buffer portion 20g can be formed as a non-modulated area (DC signal) of about several bits. 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 unit 20
It is necessary to form g relatively long. In this case, it is necessary to configure the buffer section 20g with a signal capable of self-clocking, otherwise there is a risk of bit synchronization being lost. Therefore, in this case, the buffer section 20g is set to the preamble 2
It is composed of the same signal as that required to form 0a, that is, a repetitive signal with a minimum inversion interval. Further, instead of using the repetitive signal having the minimum inversion interval, it is also possible to configure the buffer section 20g by using a repetitive signal having an inversion interval that matches the modulation rule and having a pattern that is less compatible with the sector synchronization pattern.

Effects As described above in detail, according to the present invention, even when a pattern having a sharp autocorrelation is used as a synchronization signal, missynchronization is unlikely to occur, and the detection window can be set larger than in the conventional technique. Therefore, it is possible to perform strong synchronization detection on the bit strip and to perform stable signal reproduction.

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 various modifications can be made without departing from the technical scope of the present invention. Of course, it is possible.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an optical disc system to which the present invention is applicable, and FIGS. 2 (a) to 2 (c) are explanatory diagrams showing a normal data format when recording data on the optical disc 1, and FIG. FIG. 4 is a block diagram showing one configuration example 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.
FIG. 1 is an explanatory diagram showing a data format in one embodiment of the present invention. (Description of code) 20: Sector, 21: Gap 20b: Sector synchronization, 20g: Buffer unit

Claims (1)

[Claims] 1. A digital signal recording method in which a data format is composed of a gap, a preamble, a sector synchronization section, a buffer section, and a sector address section in this order, and the sector synchronization section has a stronger autocorrelation than the preamble and the buffer section. A method of recording a digital signal, wherein a sector synchronization pattern is used and a self-clockable pattern is provided in the buffer section.