JPH03188726A - Synchronous device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a synchronization device for an information transmission system that transmits and receives serial code strings.

(Prior Art) Conventionally, in this type of information transmission system, when attempting to receive a signal composed of a serial code string, it is necessary to completely match a preset synchronization pattern from among the received code strings. Frame synchronization and bit synchronization of the received code strings are performed using the time point when a matching partial code string (synchronization word) is received as the synchronization timing.

However, if the serial code string is transmitted through a transmission path with many errors, errors are likely to occur in the received synchronization word and it will not match the set synchronization pattern.
It becomes difficult to achieve the synchronization and reception becomes impossible.

In this case, even if an error correction code is added to the information words other than the synchronization word of the serial code string to be transmitted to correct errors in the information words that occur on the transmission path, reception itself will become impossible if synchronization is not achieved. Therefore, there is a drawback that the addition of the error correction code has no meaning and does not solve any problems.

(Problem M to be Solved by the Invention) Conventional synchronization devices for receiving serial code strings as described above assume that the synchronization word completely matches a preset pattern. This has the disadvantage that it is difficult to synchronize serial code strings received via many transmission paths. Moreover, even if an error correction code is added to an information word other than the synchronization word, errors on the transmission path for the synchronization word will not be corrected, so even if a small error that can be corrected occurs in the synchronization word, There was a drawback that synchronization could not be achieved and reception became impossible.

SUMMARY OF THE INVENTION The present invention aims to eliminate the above-mentioned drawbacks and provides a synchronization device that can achieve frame synchronization and bit synchronization even if a slight error occurs in the synchronization word.

[Structure of the invention]

(Means for Solving the Problems) The present invention receives a serial code string with the longest sequence code as a synchronization word, and detects the synchronization word from the received serial code string, thereby synchronizing the received serial code string. In the synchronization device, a code generation means for generating a longest sequence code that is the same as the longest sequence code constituting the synchronization word, and a correlation between the received synchronization word and the longest sequence code generated by the code generation means are provided. and determining means for determining that the received serial code strings are synchronized when the correlation value between the synchronization word and the longest sequence code calculated by the correlation calculating means exceeds a separately set reference value. and a sampling means for sampling the received serial code string based on the point in time when it is determined by the determining means that the received serial code string has been synchronized.

Another configuration is to use a matched filter having the functions of both of these means instead of the code generation means and correlation calculation means.

(Operation) In the synchronization device of the present invention, the code generating means generates the longest sequence code that is the same as the longest sequence code that constitutes the synchronization word. The correlation calculation means correlates the received synchronization word with the longest sequence code generated by the code generation means.

The determining means determines that the received serial code string is synchronized when the correlation value between the synchronization word and the longest sequence code calculated by the correlation calculating means exceeds a separately set reference value. The sampling means samples the received serial code string based on the time point at which the received serial code string is determined to be synchronized by the determining means.

In effect, the matched filter generates a longest sequence code that is identical to the longest sequence code that makes up the synchronization word, and correlates the received synchronization word with the longest sequence code.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an information receiving device equipped with a synchronization device according to the present invention.

1 is the received code sequence and M sequence code (longest sequence code)
2 is an M-sequence code generator consisting of a shift register or delay element that generates an M-sequence code; 3
is a synchronization determination circuit that compares the correlation voltage value output from the correlator 1 with a reference voltage and determines whether synchronization has been achieved;
4 is a synchronization timing generation circuit that generates a sampling signal based on the determination signal output from the synchronization determination circuit 3;
Reference numeral 5 denotes a sampling circuit that samples and captures the information words of the serial code string received by the sampling signal output from the synchronization timing generation circuit.

Here, the M-sequence code generator 2 constitutes code generation means, the correlator 1 constitutes correlation calculation means, the synchronization determination circuit 3 constitutes determination means, and the synchronization timing generation circuit 4 and sampling circuit 5 constitute sampling means. .

FIG. 2 is a block diagram showing an embodiment of an information transmitting device equipped with a synchronization device of the present invention. 6 is a code generator that generates a serial code that is an information word; 7 is an M-sequence code generator that generates an M-sequence code that is a synchronization word; and 8 is an M-series code generator that generates an M-sequence code for the information word generated by the code generator 6. a switch circuit that switches the outputs of the code generator 6 and the M-sequence code generator 7 in order to add the M-sequence code generated from the generator 6;
Reference numeral 9 indicates a switching control unit that controls the switching timing of the switch circuit 8, and 10 indicates a serial code string as shown in FIG. This is a sending interface that sends out data to the top.

The switching control unit 9 controls the switch circuit 8 to alternately select the information word output from the code generator 6 and the synchronization word output from the M-sequence code generator 7 at appropriate timing. Create a serial code string as shown in Figure 3.

FIG. 3 is a diagram showing one frame of a serial code string sent out onto the transmission line 11 from the transmission interface 1o. The serial code string consists of a synchronization word, which is an M-sequence code, followed by an information word.

Next, the operation of this embodiment will be explained. A serial code string as shown in FIG. 3 transmitted from the transmitter shown in FIG. 2 is received by the receiver shown in FIG. 1 and input to the correlator 1. The correlator 1 correlates the input serial code string with the M-sequence code output from the M-sequence generator 2, and outputs the result to the synchronization determination circuit 3.

Here, the M-sequence code refers to the longest code sequence generated by a shift register or delay element of a certain length. The autocorrelation of such an M-sequence code is 0 bit shift, that is, it is -1 in all cases other than the synchronous state,
For a 0 bit shift, 2-1=7, which is a property common to all M-sequence codes. Since the change in correlation between O-bit shift and ±1-bit shift is linear, the graph of the M-series autocorrelation function has a triangular shape as shown in FIG. Moreover, when the N1 sequence code has a bit shift, its correlation function value becomes extremely low, so it has the best property for synchronization detection. Although it decreases as the number of errors increases, it maintains the characteristics indicating synchronized timing.

Since the M-sequence code generated from the M-sequence code generator 2 shown in FIG. 1 and the M-sequence code generated from the M-sequence code generator 7 not shown in FIG. 2 are the same, the correlator 1 If there is no error in the synchronization word of the serial code string input at
The correlator 1 obtains a correlation function as shown by the solid line in FIG. Therefore, if there is a synchronization word in the input serial code string, the correlator 1 receives the fourth
The correlation value voltage corresponding to the peak value of the solid line shown in the figure is output to the synchronization determination diagram n3. The synchronization determination circuit 3 compares the correlation value voltage inputted from the correlator 1 with a separately inputted reference voltage VF, and if the correlation value voltage is equal to or higher than the reference voltage, a synchronization word is detected and synchronization is established. This determination signal is output to the synchronization timing generation circuit 4. The synchronization timing generation circuit 4 generates a sampling signal for achieving frame synchronization and bit synchronization of the received serial code string based on the input determination signal, and outputs this sampling signal to the sampling circuit 5.

The sampling circuit 5 samples the information word portion of the received serial code string based on the sampling signal inputted from the synchronization timing generation circuit 4, and outputs it to the next stage, not shown.

By the way, if an error occurs in the synchronization word part of the serial code string input to the correlator 1 on the transmission path 11, the synchronization word with a slight error and the M-sequence code output from the M-sequence code generator 2 The correlation function shown by the dotted line in FIG. It is possible to achieve synchronization even when using Therefore, the reference voltage V of the synchronization determination circuit 3
As shown in FIG. 4, F is set to a value that allows detection of the correlation peak value of the synchronization word with a slight error as shown by the dotted line. Therefore, even if the peak correlation value output from the correlator 1 is somewhat lower than that of a case where there is no error in the synchronization word, the synchronization determination circuit 3 detects the synchronization word and determines that synchronization has been achieved. A determination signal corresponding to the synchronization timing generation circuit 4 is output to the synchronization timing generation circuit 4.

According to this embodiment, even if a slight error occurs in the synchronization word of the M-sequence code, as soon as the M-sequence code generated from the M-sequence code generator 2 and the synchronization word almost match,
Since the correlator 1 outputs a peak voltage as shown by the dotted line in FIG. 4, the synchronization determination circuit 3 can determine that synchronization has been achieved. Therefore, when communicating through a transmission path with many bit errors, frame synchronization and bit synchronization can be achieved even if a slight error occurs in the synchronization word, and a reception failure state can be avoided. Therefore,
Even when an error correction code is used for information words other than the synchronization word, it is possible to avoid reception failure due to slight errors in the synchronization word, and to utilize the effect of the error correction code.

FIG. 5 is a diagram showing another embodiment of the synchronization device of the present invention. In this example, a matched filter 12 having the functions of the correlator 1 and the M-sequence code generator 2 shown in FIG. 1 is used.
Although the number of parts of the device is reduced, other effects are the same as in the previous embodiment.

〔Effect of the invention〕

As described above, according to the synchronization device of the present invention, frame synchronization and bit synchronization can be achieved even if a slight error occurs in the synchronization word.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of an information receiving device equipped with a synchronization device according to the present invention, and FIG. 2 is a block diagram showing an embodiment of an information transmitting device equipped with a synchronization device according to the present invention. 3 is a diagram showing an example of a serial code string sent from the transmitter shown in FIG. 2, and FIG. 4 is a diagram showing the correlation value voltage characteristics (correlation function FIG. 5 is a diagram showing another embodiment of the synchronization device of the present invention. 1... Correlator 2.7... M-sequence code generator 3... Synchronization determination circuit 4... Synchronization timing generation circuit 5... Sampling circuit 6... Code generator 9... Switching Control unit 8...Switch circuit 12...Matched filter

Claims (2)

[Claims] (1) A synchronization device that synchronizes the received serial code string by receiving a serial code string with the longest sequence code as the synchronization word and detecting the synchronization word from the received serial code string. code generating means for generating the same longest sequence code as the constituent longest sequence codes; correlation calculating means for correlating the received synchronization word with the longest sequence code generated by the code generating means; and correlation calculation means. determining means for determining that the received serial code string is synchronized when the correlation value between the synchronization word and the longest sequence code calculated by the means exceeds a separately set reference value; 1. A synchronization device comprising: sampling means for sampling the received serial code string based on a time point when it is determined that the code string is synchronized. (2) Code generation means for generating the same longest sequence code as the longest sequence code constituting the synchronization word, and correlation calculation means for correlating the received synchronization word with the longest sequence code generated by the code generation means. Claim (1) characterized in that a matched filter having both functions of
) synchronization device.