JPH0275240A - Transmission scramble system - Google Patents

Abstract

PURPOSE:To always attain stable reception by devising the system such that frame synchronization is not established by a false frame synchronizing pattern signal. CONSTITUTION:A transmission signal (i) applied with transmission scramble is inputted to a bit clock reproducing circuit 8 at the reception side, a bit clock signal (j) is reproduced to form a system clock. The synchronization is established by the extraction of consecutive frame synchronizing pattern signals for each frame period in a frame synchronizing signal reproducing circuit 9, and since the transmission scramble is applied by using a pseudo random signal initialized for each N-frame period, a false frame synchronizing pattern signal is not consecutively generated for each frame period and the synchronization is not established by the false frame synchronizing pattern signal. Thus, the frame synchronization is established in an always correct timing and stable reception is attained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to scramble addition that facilitates reproduction of a transmission pit clock when receiving a digital transmission signal or reproducing a recorded digital signal. In particular, it relates to a method of performing scramble addition based on frame synchronization. INDUSTRIAL APPLICATION This invention can be widely utilized in the field of communication, broadcasting, and recording, regardless of whether it is wireless or wired.

[Summary of the invention]

Generally, frame synchronization of digital transmission signals is achieved by transmitting a specific bit pattern at frame intervals.
Establish frame timing. On the other hand, in order to facilitate the reproduction of the bit clock of the transmission signal, scrambling may be performed by adding a pseudo-random signal initialized for each frame period to the transmission signal using exclusive OR. in this case,
There is a possibility that the same bit pattern as the frame synchronization signal may occur every frame period in a transmission signal other than the frame synchronization signal, and this false frame synchronization signal causes the frame to synchronize at the wrong timing.

To solve this problem, a pseudo-random signal was initialized with a period different from the frame period and had a scrambling means added to the transmitted signal to prevent false synchronization signal bit patterns from causing frame synchronization. This prevents frames from synchronizing at the wrong timing.

Alternatively, a similar effect can be obtained by using a different pseudorandom signal for each frame period.

By using this transmission scrambling method for digital transmission, it becomes possible to always establish frame synchronization at the correct timing and perform stable reception.

[Conventional technology]

Conventionally, the scramble addition method that facilitates the recovery of the bit clock of a digital transmission signal uses a pseudo-random signal generated from an M-sequence generator, and the initialization timing of the M-sequence generator is set at the same time on both the transmitting and receiving sides. It has been attempted to match the timing of frame synchronization.

For example, in a signal that modulates the audio signal subcarrier of television satellite broadcasting (Radio Law: Standard transmission method for television, Chapter 3, Article 13, Paragraph 3), the bits immediately after the 16-bit frame synchronization signal , a method is used in which pseudorandom signals generated by a linear feedback shift register whose initial values are all 1 are added.

Initialization is performed every frame period after reproduction of the frame synchronization signal is established. Therefore, the same pseudo-random signal is added to the transmission signal every frame period.

[Problem that the invention seeks to solve]

In the prior art described above, the same pseudorandom signal is added to the transmission signal every frame period. Therefore, in a portion of a control signal or an unmodulated transmission signal that has a fixed bit pattern for a long period of time, the same bit pattern as the frame synchronization signal may occur in the frame period. Especially in the control signal part, if you set it to a specific control signal, the result of addition of pseudo-random signals will not always be the same as the frame synchronization signal.
Therefore, there is a high possibility that it will be mistakenly extracted as a frame synchronization signal and synchronization will be established at an abnormal timing. Therefore,
There is a problem in that such specific control signals must be avoided. Furthermore, if a random 5-random pattern is fixedly occurring in the unmodulated transmission signal part, then the pseudo-rung signal coincidentally coincides with the frame synchronization pattern signal after the signal is added, and synchronization occurs at the wrong timing. could be established.

When incorrect synchronization is established as described above, it is difficult to restore normal synchronization timing, causing problems such as abnormal sounds and meaningless information being displayed. The present invention has been made to solve these problems.

[Means for solving problems]

In order to avoid falling into the above-mentioned situation, the present invention has the following features:
In order to prevent the same bit pattern as the frame synchronization signal from occurring every frame period in transmission signals other than the frame synchronization signal, the pseudorandom signal added to the transmission signal is made to be different in successive frames.

That is, the transmission scrambling method according to the present invention is
When transmitting a digital signal, the transmitting side adds and scrambles the pseudo-random signals, making it easy to recover the bit clock on the receiving side.In the transmission suffrant system, a different pseudo-random signal is added for each frame period. , by separately transmitting a signal that controls the pseudo-random signal along with the frame synchronization signal,
The feature is that the pseudo-random signals generated on the transmitting side and the receiving side are made equal.

Such a configuration can be realized by separately transmitting a timing signal having a period different from the frame period and using this timing signal as an initialization timing signal for the pseudorandom signal generation circuits on the transmitting side and the receiving side.

It can also be realized by switching between a regular pseudo-random signal and a sign-inverted signal thereof as the pseudo-random signal for each frame, and separately transmitting a switching signal for identifying the two.

Furthermore, each of the transmitting side and the receiving side is equipped with a plurality of pseudorandom signal generating circuits, and different pseudorandom signals generated from these pseudorandom signal generating circuits are used for each frame to perform scrambling. This can also be achieved by separately transmitting a switching signal for identifying the signal generating circuit and making the pseudo-random signals used on the transmitting side and the receiving side equal.

[For production]

In this way, a different pseudo-random signal is added for each frame period, so that the same pit pattern as the frame synchronization signal will not occur in transmission signals other than the frame synchronization signal in subsequent frame periods.

In general, synchronization protection circuits do not establish synchronization unless a signal that matches the frame synchronization signal pattern occurs two or more times in a row, so frame synchronization will not be established due to false frame synchronization pattern signals, and it will always be stable. Reception becomes possible and the problems in the prior art are solved.

〔Example〕

Embodiments of the transmission scrambling system according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of the transmission scrambling method according to the present invention. On the transmitting side, an initialization timing signal d' obtained by dividing the frame synchronization signal a by N by an N frequency divider 4' is used. Initialization of the pseudo-random signal generation circuit 1 is performed at N frame cycles. The pseudo-random signal e generated by the pseudo-random signal generation circuit 1 is added to the information signal f by an exclusive OR circuit 5 to perform scrambling.
A transmission scramble signal g is obtained. The synchronization pattern signal generation circuit 7 uses the frame synchronization signal a to generate a synchronization pattern signal at a frame period, and generates an initialization timing signal d.
' and is added to the transmission scramble signal g by the multiplexing circuit 6 to obtain the transmission signal 1, which is then transmitted.

On the receiving side, the scrambled transmission signal l is input to the pit clock reproducing circuit 8, and the pit clock signal is reproduced as a system clock. The frame synchronization signal reproducing circuit 9 extracts the frame synchronization pattern signal from the transmission signal 1, stabilizes it using its periodicity, and obtains the frame synchronization signal k. Initialization timing regeneration circuit 10'
Now, extract the initialization timing signal from transmission signal 1,
Initialization timing signal p' using frame synchronization signal k
output stably. By inputting this initialization timing signal β' to the pseudo-random signal generation circuit 11 and initializing it at a period of N frames, a pseudo-random signal O equal to that on the transmitting side is obtained. By adding the pseudorandom signal O to the transmission signal l using the exclusive OR circuit 14, a descrambled information signal p can be obtained.

In this way, the frame synchronization signal reproducing circuit 9 is configured to establish synchronization by extracting continuous frame synchronization pattern signals for each frame period.
Since transmission scrambling is performed using a pseudo rung signal that is initialized every N frame periods, false frame synchronization pattern signals do not occur consecutively every frame period. This eliminates the problem of establishing synchronization.

Note that the initialization timing signal is not limited to the one obtained by dividing the frame period illustrated here by N, but may also be a signal having an arbitrary period that is not equal to the frame period.

FIG. 2 is a block diagram showing a second embodiment, in which the same reference numerals as in FIG. 1 indicate the same functional parts. On the transmitting side, the pseudorandom signal generation circuit 1 is initialized using the frame synchronization signal a as before, but the regular pseudorandom signal generated from the pseudorandom signal generation circuit 1 is input to the sign inversion circuit 2, A second pseudorandom signal C, which is a sign-inverted signal, is obtained. The regular pseudo-random signal C, which is the first pseudo-random signal, and the second pseudo-random signal C, which is the sign-inverted signal, are sent to the switching circuit 3 so as to be used alternately every frame period.

The divide-by-2 circuit 4 receives the frame synchronization signal a, divides it by two, and sends a switching signal d that repeats high and low levels every frame period to the switching circuit 3 and the multiplexing circuit 6. . The switching circuit 3 switches between a regular pseudo-random signal and a pseudo-random signal C obtained by inverting the sign of the normal pseudo-random signal every frame period using this switching signal d, and outputs a pseudo-random signal e.

The exclusive OR circuit 5 adds this pseudo-random signal e to the information signal f to obtain a scrambled transmission scramble signal g. The multiplexing circuit 6 adds the frame synchronization pattern signal outputted from the synchronization pattern signal generation circuit 7 and the switching signal d to the transmission scramble signal g, and outputs the transmission signal 1.

On the receiving side, a pit clock reproducing circuit 8 regenerates a bit clock signal J from the transmission signal 1 subjected to transmission scrambling. In the frame synchronization signal reproducing circuit 9, the transmission signal 1
The frame synchronization pattern added to the frame synchronization pattern is extracted, stabilized, and a frame synchronization signal k is output. The switching signal reproducing circuit 10 extracts the switching signal from the transmission signal 1 and stably outputs the switching signal l using the frame synchronization signal k.

The pseudo-random signal generation circuit 11 generates frame 1 and synchronization signal k.
A regular pseudo rung 18 signal m, which is a first pseudo random signal, is generated at the frame period, and a second pseudo random signal n, which is a sign inverted signal, is also generated by the sign inverting circuit 12 to which this signal is input. obtain. The regular pseudo-random signal m and the second pseudo-random signal n, which is its sign-inverted signal, are output alternately for each frame using the switching signal β in the switching circuit 13, and the pseudo-random signal 0 after this switching is The information signal p is added to the transmission signal l by the exclusive OR circuit 14 and descrambled.
get.

In this way, the transmission scramble is inverted every frame period, and false synchronization patterns do not occur in consecutive frames, and the frame synchronization signal regeneration circuit synchronizes with the false synchronization pattern signal. will no longer be established.

FIG. 3 is a block diagram showing the third embodiment, in which the same reference numerals as in FIGS. 1 and 2 indicate the same functional parts. On the transmitting side, two different pseudo-random signal generation circuits 18, I
There are a plurality of pseudorandom signals S and B, both of which are initialized by a frame synchronization signal a and output different first and second pseudorandom signals S and C, respectively.

The pseudo-random signals S and C are switched for each frame in the switching circuit 3 using a switching signal d obtained by frequency-dividing the frame synchronization signal a by a frequency divider circuit 4. The pseudo-random signal e, which is this output signal, is added to the information signal f in an exclusive OR circuit 5, and a transmission scramble signal g is added to the information signal f.
get. The frame synchronization pattern signal and the switching signal d are added to the transmission scramble signal g in the multiplexing circuit 6 to obtain the transmission signal 1, as in the case of FIG.

On the receiving side, a pit clock reproducing circuit 8 reproduces a bit clock signal from the transmission signal j subjected to transmission scrambling. The frame synchronization signal reproducing circuit 9 extracts the frame synchronization pattern, and after confirming that the synchronization pattern can be continuously received at the frame period, stably outputs the frame synchronization signal k. Switching signal regeneration circuit 10
extracts the switching signal from the transmission signal 1 and uses the frame synchronization signal k to generate the switching signal! output stably.

The pseudorandom signal generation circuits 11A and 11B correspond to the pseudorandom signal generation circuits LA and IB on the transmitting side, respectively, and output first and second pseudorandom signals m and n of the same series, respectively. The pseudo-random signals m and n are alternately switched and output for each frame by the switching signal p in the switching circuit 13, and a pseudo-random signal 0 is obtained. This pseudo-random signal O is added to the transmission signal ] by an exclusive OR circuit 14 to obtain a descrambled information signal p.

In this way, transmission scrambling is performed using a different series of pseudo-random signals for each frame period, so false synchronization pattern signals will not occur in consecutive frames, and the frame synchronization signal regeneration circuit will generate false synchronization signals. Synchronization is no longer established by pattern signals.

〔Effect of the invention〕

In the conventional technology, transmission scrambling was performed by adding the same pseudo-random signal to the information signal every frame period. Therefore, in the part of the control signal where there is a continuous fixed pit pattern for many frames, the same bit pattern as the frame synchronization pattern signal may appear every frame period after adding the pseudo-random signal. There is a problem in that synchronization is established at the wrong timing by using this as a frame synchronization pattern signal.

In addition, there is a possibility that even a portion of the unmodulated information signal may coincidentally coincide with the frame synchronization pattern signal after addition of the pseudorandom signal, thereby establishing erroneous synchronization.

In the present invention, when adding a pseudo-random signal to an information signal and performing scrambling, a method is used in which different pseudo-random signals are added between successive frames, rather than adding the same pseudo-random signal for each frame. . To this end, a timing signal with a scrambling period different from the frame period or a switching signal for switching between different pseudo-random signals is added and transmitted to the receiving side. By doing this, on the receiving side, false synchronization pattern signals will not occur in consecutive frames in the portion where the transmission scramble is added.

In a general synchronization protection circuit, synchronization is not established unless a synchronization pattern signal is extracted two or more times in a row in a frame period, so synchronization will never be established due to a false synchronization pattern signal, and the original frame synchronization pattern will always be used. The signal allows synchronization to be established at the correct timing.

[Brief explanation of the drawing]

1 to 3 are block diagrams showing first to third embodiments of the transmission scrambling system according to the present invention, respectively. 1, LA, IB, 11.11 people, 11B...Pseudo random signal generation circuit 2.12...Sign inversion circuit 3.13...Switching circuit 4...2 frequency dividing circuit 4'... N frequency divider circuit 5.14...Exclusive OR circuit 1], 7-, -6...Multiplex circuit 7...Synchronization pattern signal generation circuit total...Pit clock regeneration circuit 9...Frame Synchronous signal reproducing circuit 10... Switching signal reproducing circuit lO'... Initialization timing reproducing circuit a, k...
・Frame synchronization signals c, e, m, n, o...pseudo random signals d, β...switching signals d', A'...initialization timing signals f, p...
・Information signal g...Transmission scramble signal h...Synchronization pattern signal 1...Transmission signal j...Pit crop signal OP Zato et al Tomi'll! ″ 1 + So [ Shiba Mi

Claims (1)

[Claims] 1. In a transmission scrambling method in which pseudo-random signals are added and scrambled on the transmitting side when transmitting a digital signal, and the bit clock is easily regenerated on the receiving side, a pseudo-random signal that differs for each frame period is used. A transmission scrambling method characterized in that the pseudo-random signals generated on the transmitting side and the receiving side are equalized by separately transmitting a signal for controlling the pseudo-random signal together with a frame synchronization signal. 2. The transmission scramble according to claim 1, characterized in that a timing signal having a period different from the frame period is separately transmitted, and the timing signal is used as an initialization timing signal of pseudo-random signal generation circuits on the transmitting side and the receiving side. method. 3. The transmission according to claim 1, characterized in that a regular pseudo-random signal and a sign-inverted signal thereof are switched and used as the pseudo-random signal for each frame, and a switching signal for identifying the two is separately transmitted. Scramble method. 4. Each of the transmitting and receiving sides is equipped with a plurality of pseudorandom signal generation circuits, and different pseudorandom signals generated from these pseudorandom signal generation circuits are used for each frame to perform scrambling, and these pseudorandom 2. The transmission scrambling system according to claim 1, wherein a switching signal for identifying the signal generating circuit is separately transmitted, and pseudo-random signals used on the transmitting side and the receiving side are made equal.