JPS59138155A - Method for transmitting digital signal - Google Patents

Abstract

PURPOSE:To suppress the waveform of a synchronizing signal from being deformed due to the interference between codes in case of a long range transmission when a signal pattern violating the rule of a data modulating system is used to a frame synchronizing pattern section to part each frame from plural frames. CONSTITUTION:A digital signal train is split into plural frames having a prescribed number of bits and the one frame is constituted of the frame format. The first 4 bits are used as a frame synchronizing pattern section S and the 5th-28th bits are used as a digital audio sampling data. The tail 2.5-bit part of the frame synchronizing pattern (preamble) of the head 4-bit is constituted so that the 1-bit length of the inverting interval is arranged next to the 1.5-bit as the main synchronizing period.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention provides P
The present invention relates to a digital signal transmission method for serially transmitting frame-divided digital signals such as CM digital audio signals.

[Background technology and its problems]

In recent years, analog signals such as audio signals and human voice signals have been converted into PCM (Pu1se Code M
odulation) method,
Transmission (recording and recording) via signal transmission media (including recording media)
(including playback) are becoming more frequent. In such digital audio signals, one frame is set corresponding to one word of multi-bit digital audio sample data obtained by quantizing and encoding one sample value of the original analog signal. There is. In this case, the data to be transmitted includes, in addition to this digital audio sample data, error prevention data, user-definable alphanumeric data, and various other information described below, as necessary. This may include channel state information, information indicating the reliability of the above sample data, etc. In addition, other data may be required in future applications, and if necessary, auxiliary information, which will be described later, although the quality will be lower. It would be desirable to also be able to transmit data for digital audio channels.

The following properties are required for a method of serially transmitting digital signals containing various types of data.

That is, first of all, in order to enable transmission with or without AC coupling and to ensure threshold detection even in the case of electrical systems, a DC free type It is necessary to make the transmission waveform precise. Next, the transmitted waveform is polarity independent (polar
ity-free),
This contributes to the simplification of the device without affecting the transmission signal even if one and the other of a pair (two) transmission lines such as a twisted pair are inserted incorrectly.

Next, it is necessary that hardware implementation be simple and easy. Furthermore, it is necessary to satisfy the transmission distance when applied to broadcasting stations, studios, etc.

A so-called digital FM system is known as a digital signal modulation system that satisfies all of these requirements. This Dijikuru FM method is %]'l”O”
An inversion (trans peak on) is always placed at the edge (or boundary) of each hint of the binary data in This method is expressed as a signal waveform as shown in FIG. 1 in correspondence with digital binary data. In this digital FM signal, when the data bit period is T, the interval from the above inversion to the next inversion is T
Since the bit clock signal is either /2 (0,5 bits long) or T (,1 bits long), it is extremely easy to detect and hold the bit clock signal. In addition, the above DC-free and p
The condition of polarity-free is also satisfied.

In ancient times, there were 17...
When a digital signal string, such as data, is divided into a plurality of frames having a fixed number of bits and transmitted serially, it is necessary to reliably and accurately extract the synchronization signal of each frame. Therefore, it has been proposed to insert a frame synchronized portion of a specific signal pattern between adjacent frames that violates the modulation rules or conversion rules of the digital FM system. This frame synchronization pattern section is called a preamble when it is placed at the beginning of a valley frame, and is sometimes called a postamble when it is placed at the end of each frame.

By the way, when long-distance transmission is carried out using conductive cables, the received waveform is distorted, especially in the part that satisfies the conversion rule of the digital FM system mentioned above (the data part of the frame), even though binary discrimination can be performed. In the part where the above rules are violated (frame synchronization pattern part), a situation may occur where the binary values of the signal cannot be accurately reproduced due to so-called inter-symbol interpolation. This becomes noticeable, for example, when a 05-bit length is placed immediately after a 5-bit length as a signal pattern inversion interval. If such a frame synchronization signal cannot be regenerated reliably, not only will it be impossible to divide multiple frames accurately, but the accuracy of determining the timing of each data in an I frame will decrease, and the data It may also cause misreading.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and when a signal pattern that violates the rules of the data modulation system is used in the frame synchronization pattern section for dividing each frame of a plurality of frames, it is possible to It is an object of the present invention to provide a digital signal transmission method that can suppress as much as possible the distortion of a synchronizing signal waveform due to code amount interference during transmission.

[Summary of the invention]

In order to achieve the above object, according to the digital signal transmission method of the present invention, a digital signal string is divided into a plurality of frames having a fixed number of bits, and the digital signal in the divided frames is Convert to '0' or vice versa into a code string with a combination of l-bit length and 05-bit length between inversion positions, and insert a synchronization pattern section between the adjacent divided frames. The synchronization pattern part has a length of 4 bits or more, and a 1-bit length inversion interval is arranged immediately after a 15-bit length inversion interval. It is characterized by having a main synchronization period of 25 bits long and an auxiliary synchronization period of 15 bits or more.

Further, other features of the digital signal transmission method of the present invention are as follows:
In the digital signal transmission method having the above characteristics, the synchronization pattern section is composed of the main synchronization section with a length of 2.5 bits and the auxiliary synchronization section with a length of 1.5 bits arranged before or after the main synchronization section. , for this auxiliary synchronization interval,
Three types of patterns are formed by combining inversion intervals of 1 bit length and 05 bit length, and a synchronization pattern portion having any one of these patterns is inserted between the adjacent frames.

Still another feature of the present invention is that in the digital signal transmission method having each of the features described above, one type of synchronization pattern part of the three types of synchronization pattern parts having the three types of patterns described above is used as an ill synchronization pattern part of l frame for every n frames. At the same time, one of the remaining two types of synchronization pattern parts is used as the second synchronization pattern part for one frame per m frames, the other is used as the third synchronization pattern part for other frames, and The method is to sequentially and repeatedly transmit m-channel digital signals at m-frame periods using one frame cycle. However, the above n.

Both m are integers, n)m, for example, n=256
, m=2.3.4. Note that it is of course possible to transmit a single channel digital signal with m= ].

〔Example〕

A preferred embodiment of the digital signal transmission method of the present invention will be described below.

A digital signal string is divided into a plurality of frames each having a fixed number of bits (for example, 32 bits), and one frame is configured in a frame format as shown in FIG. 2, for example. The first 4 bits of this one frame are used as the frame synchronization pattern section S, which is the gist of the present invention.
), 24 bits from the 5th bit to the 28th bit,
For example, one sample value of an audio signal is converted into PCM and used as digital audio sample note data. In this case, the 4 bits from the 5th bit to the 8th bit are converted into hit X1 of digital audio auxiliary sample data (hereinafter referred to as auxiliary data).
.about.X4, and the 9th bit to the 28th bit may be used as bits D1 to D2o of the PCM digital audio sample data. Next, 2
The 9th bit is used as a data validity determination bit V, the 30th bit is used as a user's bit (U), the 31st bit is used as a channel status data bit C, and the 32nd bit is used as a parity pit.

In this case, the user's bit U and channel status data bit C are l in the block format shown in Figure 2.
Each block constitutes one word.

That is, in this embodiment, for example, 256 frames are transmitted as one block, and in each block, the user data and channel state data are each transmitted as information of 1 word of 256 bits.
I am sending it.

Furthermore, like a stereo audio signal, sample data words of two left and right channels are transmitted alternately every frame (with a period of two frames), or data words of m channels (m is an integer) are generally transmitted. It is also possible to transmit at a period of m frames.

The synchronization pattern section (or preamble) S also specifies the first frame of one block and the frame that becomes the first channel of m channels.

In other words, FIG. 3 shows the 4-bit length synchronization pattern section.
FIG. 2 is a signal waveform diagram showing a specific example of the signal waveform diagram, in which each pattern instructs frame synchronization, the first pattern (preamble I) instructs block synchronization, and the second pattern (preamble ■) instructs frame synchronization among multiple channels. The third pattern (preamble (■))' indicates the first channel (first channel) of the channel, and the third pattern (preamble ■)' indicates the channels other than the first channel among the plurality of channels. Now, convert 1 bit to 2
The I cell is divided into 05 bits long), NI(,
When displaying a cell sequence using the Z (non-return to zero) method, preamble 1:11 01 11 00 preamble U: ] Q 01 11 00 preamble 11:10
It becomes 10 00 1+. That is, the trailing 25-bit length portion of the synchronization pattern section (preamble) is the main synchronization period, and the inversion interval is 1.5 bits long, followed by 1-pitch I.
・It is structured so that the length is arranged.

On the other hand, the part other than the synchronization pattern part S in the frame format of FIG. It is converted into a code string consisting only of the combination of month bit length and 05 bit length, and the part where the inversion interval is 15 bits long in the main synchronization section of the synchronization pattern section S violates the conversion rule of the digital PM system. This makes extraction on the receiving side extremely easy.

An example of the cell sequence in the synchronization pattern section is as follows:
This pattern is automatically selected when the cell immediately before the synchronization pattern section is lol, but when the cell immediately before the synchronization pattern is °1°, Preamble! :00 10 00 II preamble 11:01 10 00 +1 preamble 1:0
1 01 ] ] 00. These are the third
The polarity of the signal waveform shown in the figure is reversed, and because of the polarity-independent nature described above, they each represent the same content.

By the way, as a prior art of the present invention, it has already been proposed to set a synchronization pattern part (preamble) of a signal waveform as shown in FIG. 4, for example. has the following problems.

First, preambles I and ■ in FIG. 4 have an inversion interval of 1.
Since there are two portions each having a length of 5 bits, the receiver side must determine which portion is to be used as the reference timing for frame synchronization, which complicates the circuit configuration.

Next, the preambles ■ and ■ in FIG.
．． Since the 05-bit length is allocated immediately after the 5-bit length, when direct distance transmission is performed via an electrical transmission cable, waveform distortion occurs due to so-called code amount interference, and the 05-bit length is Parts may not be completely replayable.

That is, FIGS. 5 to 7 show signal waveforms appearing at the receiving end when a digital signal is transmitted via a 200 m electrical transmission cable, and show cases where the bit clock frequency fc is different. ing. In Figure 5, fc =3.078MH
z, which corresponds to two-channel transmission (48 kHz x 32 x 2) when the sampling frequency is 43 kHz. In FIG. 6, fc =3.686 MHz, which corresponds to 12 times the fC in FIG. In Figure 7, f
c = 4.05MHz, which is about 13 of fc in Figure 5.
Equivalent to twice as much. In addition, the transmission driver and receiver are 9638.9637 compliant with gIA standard R8-422.
is used. Furthermore, each person in FIGS. 5 to 7 has an IT
(1 bit length) is shown, and each B shows an example in which 0.5T is placed immediately after 1.5T.

As is clear from these figures 5 to 7, in the part where the inversion interval is 1.5 T, the amplitude of the signal waveform at the receiving end is different from that of other data parts (the inversion interval is 1.5 T and 0.5 T). Therefore, even if the transmission frequency characteristics etc. are set so as to cross the threshold TH in the other data parts, the threshold TH will be reached at 0.5 T immediately after 1 and 5 T. Sometimes I don't reach it. In other words, as shown in FIG. 7B, even though it is possible to reproduce binary information in the data part, the threshold value TH is not reached at the 0.5 T part immediately after 1.5 T, so the threshold value TH is not reached in this part. Binary information reproduction is no longer performed. On the other hand, as shown in Figure 7A, 15
If IT is placed immediately after T, the binary information will be completely reproduced. In addition, in the case of FIGS. 5 and 6, A,
Although binary information can be reproduced using either of the B waveforms, it is clear that the so-called eye pattern of B is more deteriorated than that of A.

As is clear from the above, according to the embodiment of the present invention, a unique inversion interval of 15T is provided in the synchronization pattern section inserted between adjacent frames, and immediately after this 1.5T, there is always a Since the IT inversion interval is set to be continuous, as long as the binary information in the data part other than the synchronization pattern part within the frame can be reproduced, the synchronization signal can also be reliably reproduced.

By the way, the correspondence between the three types of synchronization pattern parts (preamble I, H, l) shown in FIG. For , one polarity is 25
Since the other polarity of T1 is 15T, which slightly deviates from the DC-free conditions mentioned above, block synchronization that occurs least frequently during signal transmission (for example, one point per 256 frames) is used. )c!
: It is preferable to use it as follows. The remaining preamble ■.

Regarding (2), for example, when transmitting one channel, frames other than the above-mentioned block synchronization frame (256
255 frames), only the preamble ■ is used as frame synchronization, and the a channel A is like a stereo left and right channel.

When transmitting B alternately every frame (with a period of two frames), one preamble ■ (or l) is sent to the frame of channel A other than the above block synchronization, and the other preamble Preamble ■ (or ■)
It is convenient to use each of them. Furthermore, if, for example, four channels of X channels A to D are to be transmitted repeatedly in a four-frame period, the i-side preamble ■ (or , the other preamble ■ (or ■) may be used for each frame of channels B, C, and D, respectively. Furthermore, if we also consider the polarity of the signals before and after the preamble part, the preamble ■ more completely satisfies the conditions for direct current suppression (DC-free), and this preamble ■ is the one that is used for actual signal transmission. It is preferable to select the one that appears most frequently in the list.

It should be noted that the present invention is not limited to the above-mentioned embodiment. For example, the first half 15-bit auxiliary synchronization section and the second half 25-bit main synchronization section in the 4-bit long synchronization pattern section shown in FIG. 3 as shown in Figure 8.
Different types of patterns may be used. This is the cell
According to the NRZ display of the sequence: Preamble I:]] 10 01 10 Preamble n:]] 10 01 00 Preamble III:
]l 10 0+ 01. These all show the case where the cell immediately before the preamble is "0", and if the cell immediately before the preamble is "pi", the polarity of the preamble pattern is reversed, and the preamble 1 :00 01 10 01 preamble 11:00 01 10 11 preamble 1:00
01 10 10 may be used.

Furthermore, it is possible to freely provide a synchronization pattern section with a bit length longer than 4 bits, and it is also possible to arrange the synchronization pattern section at the end of one frame, or to set the relationship between data words and frames arbitrarily. A synchronization pattern section may be placed in the middle of a word.

〔Effect of the invention〕

As is clear from the above explanation, according to the digital signal transmission method according to the present invention, at least the data portion in one frame is converted into a code string by a combination of inversion intervals of 1 bit length and 05 bit length. , a unique one at a predetermined position within the synchronization pattern section for frame synchronization.
Because there is a main synchronization period of 2.5 bits long with a 1-bit long reversal interval immediately after a 5-bit long reversal interval,
The above 15-bit length inversion interval can be clearly distinguished from other data parts, which not only facilitates frame synchronization extraction, but also ensures that the only 1.5-bit length inversion interval is placed at a fixed position within the synchronization pattern. As a result, the synchronization timing for one frame can be determined uniquely and accurately.Moreover, even when transmitting over long distances using electrical transmission cables, there is extremely little interference in the amount of code, making it possible to reproduce the data part. The synchronization pattern portion can be reproduced as reliably as possible.

Furthermore, by setting the length of the synchronization pattern part to 4 bits or more, one Three or more types of patterns can be formed by combining only the bit length inversion interval and the 0.5 bit length inversion interval, and for example, it is possible to distinguish between block synchronization when transmitting n frames in one block and other frame synchronizations. It is also possible to do so. In addition, the three types of synchronization pattern sections are used as the block synchronization described above, and as synchronization of a frame indicating the first channel (first channel) when m channels are sequentially and repeatedly transmitted in m frames at intervals. Each can be used as frame synchronization other than synchronization.

[Brief explanation of drawings]

FIG. 1 is a waveform diagram showing an example of a digital signal waveform modulated by the digital FM method, FIG. 2 is a diagram showing an example of the frame format and block format of digital signal transmission applied to the present invention, and FIG. The figure is a waveform diagram showing a specific example of the synchronization pattern section which is the main part of the present invention, FIG. 4 is a waveform diagram showing an example of the synchronization pattern section in the prior art of the present invention, and FIGS. 5 to 7 are the receiving end shows the signal waveform near the synchronization pattern part in A
is an example of the present invention, B is a waveform diagram showing an example of the prior art,
No. 8- is a waveform diagram showing another specific example of the synchronization pattern section which is the main part of the present invention.

Claims (3)

[Claims] (1) Divide a digital signal string into multiple frames with a fixed number of bits, and change the digital signal in the divided frames so that the interval between inversion positions from "1° to"θ' or vice versa is 1 bit long. and 0.05 bit length according to a certain conversion rule, and inserts a synchronization pattern part between the divided adjacent frames to transmit it as a signal indicating the frame division, and also transmits the synchronization pattern as a signal indicating the frame division. The main synchronization section has a length of 4 bits or more, and has a 25-bit length main synchronization period with a 1-bit length reversal interval immediately following a 1.5-bit length reversal interval, and an auxiliary synchronization period of L55 bit length. 1. A digital signal transmission method comprising: (2) The synchronization pattern section is divided into the main synchronization section of 2.5 bit length and 15 patterns arranged in front or behind it.
For this auxiliary synchronization period, three types of patterns are formed by combining the inversion interval length and the 0.5 bit length, and any one of these patterns is 2. The digital signal transmission method according to claim 1, further comprising inserting a synchronization pattern section having a synchronization pattern section between said adjacent frames. (3) One of the three types of synchronization pattern sections having the above three types of patterns is used as the first synchronization pattern section for one frame every n frames, and one of the remaining two types of synchronization pattern sections is used as the first synchronization pattern section for one frame every n frames. one frame per m frame is used as the second synchronization pattern part, the other is used as the third synchronization pattern part of the other frame, n
The digital signal transmission method according to claim 2, characterized in that digital signals of m channels are transmitted sequentially and repeatedly in m frame periods as one frame frame block, where n and m are integers, and n)m)k. .