JPH01278142A - Modulating system for transmission line signal - Google Patents

Abstract

PURPOSE:To reduce same code continuation length and also to suppress the occurrence of the same code continuation itself by modulating branched signals of two series having the same contents via two M-series generators having different numbers of stages and selecting and transmitting a signal series having small code continuation length. CONSTITUTION:A speed converting circuit 7 inputs an input signal series subjected to speed conversion to a branch circuit 8. 1st and 2nd M-series signal generators 10 and 13 having different numbers of stage produce 1st and 2nd M-series signals which are supplied to 1st and 2nd exclusive OR circuit 11 and 14 respectively. Then the 1st modulation input signal series are different from the 2nd modulation input signal series. A selection circuit 15 adds information showing the specific series where the modulation is applied to the remaining bit of the signal having the smaller continuous same polarity signal length by means of the output of a specific M-series signal generator. Then said added information is outputted to a transmission line 6 as a transmission line signal. Thus it is possible to reduce the same code continuation length and at the same time to suppress the occurrence of the same code continuation itself.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a transmission line signal of a PCM communication system, and in particular to a transmission line signal modulation system that can obtain a random signal with a mark rate of 1/2 of the transmission line signal. Regarding.

[Conventional technology]

Generally, the transmission path code in the PCM communication system is as follows:
(A) Timing extraction is easy on the receiving side; (B)
) A so-called balanced code is desirable because the circuit configuration is simple and the probabilities of occurrence of 1 and O are approximately equal and a constant DC component is obtained.

FIG. 2 is a block diagram showing a conventional transmission line signal modulation method. In the figure, 1 is an input terminal into which an information signal is input, 2 is a speed conversion circuit that adds 1 extra bit to every n bits of this information signal and outputs an input signal sequence whose speed has been converted, and 3 is a constant speed conversion circuit. 4 is an M-series signal generator which outputs an M-series signal and is reset by inputting this reset pulse; 5 is an exclusive OR circuit; and 6 is a transmission line. be.

Next, the operation of the transmission line signal modulation method with the above configuration will be explained. First, the information signal input to the input terminal 1 is input to the speed conversion circuit 2. The speed conversion circuit 2 adds one extra bit to every n bits and outputs the speed-converted input signal sequence to the exclusive OR circuit 5. On the other hand, M
The sequence signal generator 4 outputs the M sequence signal reset at regular intervals by the reset signal to the exclusive OR circuit 5. The exclusive OR circuit 5 modulates the input signal sequence and outputs the obtained transmission line code to the transmission line 6. When looking at this transmission line signal over a relatively long time,
The probability of occurrence of 1 and 0 is almost the same, that is, the mark rate is approximately 1.
/2 random signal is obtained.

[Problem to be solved by the invention]

The conventional transmission line signal modulation method described above is configured to modulate the input signal sequence with an M-sequence signal that is reset at regular intervals, but in a short period of time such as this reset pulse period, depending on the input signal, the signals may have the same sign. There are many cases where continuity occurs, making it difficult to extract the timing on the receiving side.
The identification margin may deteriorate due to fluctuations in the DC component. In addition, the number of consecutive identical codes can only be grasped probabilistically, and even if all the codes are the same, there is a drawback that it cannot be determined in terms of probability.

[Means to solve the problem]

The transmission line signal modulation method according to the present invention has a transmission line signal modulation method of
A means for converting the speed so as to add surplus bits, a means for branching the speed-converted input signal sequence into two, and generating an M-sequence signal for taking an exclusive OR with the two-branched signal sequence. The M-sequence signal generator has two M-sequence signal generators with different numbers of stages, and a circuit that selects which exclusive OR output is to be sent out as a transmission line signal and provides the selection information as an extra signal.

[Effect]

This invention can significantly shorten the length of the same code sequence, and can also suppress the occurrence of the same code sequence itself.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of a transmission line signal modulation method according to the present invention. In the figure, an information signal is input to the input terminal T&, an input signal sequence whose speed has been converted by adding 1 surplus bit every n bits is output from the output terminal 7b, and block information is output from the output terminal 7c. 8 is a branch circuit that branches the speed-converted input signal series into two; 9 is a first reset terminal to which the first reset pulse is input; 10 is a circuit that is reset by this first reset pulse; a four-stage first M-sequence signal generator that is reset at regular intervals and generates a first M-sequence signal; 11;
1 is a first exclusive OR circuit that modulates the branched input signal sequence with the first M sequence signal and outputs the first modulated input signal sequence; 12 is a second reset terminal to which the second reset pulse is input; 13 is this A second M-sequence signal generator 14 having an n-stage configuration that is reset at regular intervals by a second reset pulse and generates a second M-sequence signal; A second exclusive OR circuit 15 outputs two modulated input signal sequences, and 15 selects the shorter signal sequence with the same code continuous length among the first modulated input signal sequence and the second modulated input signal sequence. This is a selection circuit that adds information on whether the signal sequence of is used as a transmission path code to the surplus bits.

Next, the operation of the transmission line signal modulation method with the above configuration will be explained. First, the information signal input to the input terminal 1 is input to the speed conversion circuit 7. This speed conversion circuit T outputs an input signal sequence whose speed has been converted by adding one surplus bit every n bits from its output terminal 7b to a branch port -8, and selects a block information signal from its output terminal 7c. Output to circuit 15. Then, this branch circuit 8 branches this speed-converted input signal series into t-2, each with a first
Exclusive OR circuit 11 and second exclusive OR circuit 14
Output to. Then, the first exclusive OR circuit 11 modulates one of the branched input signal sequences with the first M sequence signal that is reset at regular intervals, and outputs the first modulated input signal sequence to the selection circuit 15. On the other hand, the second exclusive OR circuit 14 modulates the other branched input signal sequence with the second M sequence signal and selects the second modulated input signal sequence by the selection circuit 15.
Output to. At this time, the signals input to one input terminal of the first exclusive OR circuit 11 and the second exclusive OR circuit 14 are both information signals after speed conversion, and their contents are exactly the same, but the other Since the first M-sequence signal and the second M-sequence signal input to the input terminals of the first M-sequence signal generator 10 and the second M-sequence signal generator 13 are different in number of stages, the first modulated input signal sequence and the second modulated input signal sequence are different from each other. The resulting signal is different from the input signal series. Therefore, the selection circuit 15 uses the block information output from the output terminal 7C of the speed conversion circuit 7 to select the n consecutive information bits of the first modulation input signal series and the second modulation input signal series and the information bits added thereto. At the same time as detecting the surplus bit position of 1 bit, continuous signals of the same polarity included in the n information bits are combined into the first modulated input signal sequence and the second modulated input signal sequence.
The modulated input signal sequences are compared, and information indicating which M sequence generator output was used to modulate the sequence is added to the surplus bits of the shorter signal of consecutive same polarity signal length and transmitted. It is output to the transmission line 6 as a line signal. Although the number of successive identical codes in this transmission path signal can only be determined probabilistically, the length of consecutive identical codes can be significantly shortened, and at the same time, it is possible to suppress the occurrence of consecutive identical codes themselves.

〔Effect of the invention〕

As explained in detail above, according to the transmission line signal modulation method according to the present invention, two signal streams having the same content that are branched into two are modulated by the outputs of M-sequence generators having different numbers of stages. This has the advantage that a signal sequence with a short code sequence length can be selected and output as a transmission line signal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a transmission line signal modulation method according to the present invention, and FIG. 2 is a block diagram showing a conventional transmission line signal modulation method. DESCRIPTION OF SYMBOLS 1...Input terminal, 6...Transmission line, 7...Speed conversion circuit, 8-...Branch circuit, 9...1st reset terminal, 1o...1st M Series signal generator, 11.
. . . 1st exclusive logic circuit, 12 . . . -second reset terminal, 13 . . . 2nd M sequence signal generator, 14 .
...Second exclusive OR circuit, 15...Selection circuit.

Claims (1)

[Claims] In a transmission line signal modulation method that takes the exclusive OR of the input signal sequence to which a surplus bit has been added after speed conversion and the output signal of an M-sequence signal generator, the speed is converted so that one surplus bit is added to every n bits. means for branching the speed-converted input signal series into two, and means for calculating an exclusive OR of each of the two branched input signal series and each output signal of an M-sequence signal generator having a different number of stages. and a predetermined consecutive n of output signals obtained by exclusive ORing.
It is characterized by comprising means for transmitting the shorter sequence of consecutive same polarity signals in a block of bits as a transmission line signal, and adding information as to which sequence is used as a transmission line code to the surplus bits. Transmission path signal modulation method.