JPS58195336A - Communication system - Google Patents

Abstract

PURPOSE:To transmit an input digital signal on the same line at the same time, by adding an amplitude to an input analog signal, multiplying and modulating the result by a digital signal where the maximum value of consecutive zeros is limited, and designating the digital signal as a carrier. CONSTITUTION:The input analog signal 20 is added with a prescribed amplitude generated at a DC generating circuit 22 from an addition circuit 23. The input digital signal 21 is converted into a binary digital code series where the maximum value of consecutive zeros is limited to a prescribed value at a code conversion circuit 24, multiplied and modulated at a multiplication circuit 25 by the said analog signal and transmitted to a transmission line 26. A reception signal is line-equalized at a line equalizer 27 and an output signal 33 is obtained at an analog signal extracting circuit 28. The ditital signal is shaped at a waveform equalizer 29 and discriminated at a discrimination circuit 30 by using the timing wave of a timing extraction circuit 31. This signal series is inverted for the code conversion at the transmission side with a code conversion circuit 32 and an output signal 34 is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a communication system for simultaneously transmitting analog signals and digital signals over the same line.

Background of the Technology FIG. 1 is a block diagram of a typical communication system that simultaneously transmits analog signals and digital signals on the same line. (For example, Kajiwara, Sasayo: [A Study of Data Over Voice Subscriber Line Transmission System] 1985 National Conference of Electronics and Communication Studies, N111738) On the transmitting side, the input digital signal 2 is passed through a DC component suppression code conversion circuit. The input analog signal 1 is frequency-division multiplexed by the demultiplexer 4 and sent to the transmission line 5. On the receiving side, line equalization is performed using an equalization amount of 6, and a branching filter 7 separates the frequency of the analog signal and the digital signal to obtain an output analog signal 12. On the other hand, the digital signal is waveform-shaped by a waveform modification amount of 8, and a timing signal is generated by a timing extraction circuit 11 from the waveform-shaped pulse train. The nine waveform-shaped pulses are identified by a discriminator 9 using a timing signal.

The identified and reproduced signal sequence is subjected to an inverse code conversion for DC component suppression by a code conversion circuit 10 to obtain an output digital signal 13.

FIG. 2 shows the frequency bands used for analog signals and digital signals of the frequency division side strip 1 method shown in FIG. 1. Sa and Sd are the power spectrum characteristics of the analog signal and digital signal at the output terminal of the line equalization unevenness, and ygpFdti are the analog signal band and digital signal band, respectively.

Prior Art and Problems As mentioned above, in the conventional communication system, analog signals are converted into digital signals, and the clock frequency is 10 to 10 times higher than that of digital signals.
Low range J1 of about 20Ls! l, insert into skill band, D
-,,,J,l□,5,gabtu,',swear,. □In digital waveform transmission, even if code conversion is performed to suppress the DC component on the sending ffi side, there is a drawback that waveform distortion due to low frequency cutoff becomes large. On the other hand, if the clock frequency of the digital signal is increased in order to reduce the influence of waveform distortion due to low-frequency cutoff, the amount of noise increases and the S/N ratio deteriorates significantly. Furthermore, in order to guarantee the quality of analog signals, a duplexer that performs frequency multiplexing and demultiplexing is required to have stable and highly accurate characteristics. Furthermore, the receiving apparatus has the disadvantage that rounding requires separating the analog signal and digital signal and adjusting the equalization amount under good conditions, making the adjustment complicated.

Purpose of the Invention In order to eliminate these drawbacks, the present invention adds a constant amplitude value to an input analog signal, limits the maximum value of consecutive zeros to a constant value, performs multiplication modulation with a 92-level digital signal sequence, and generates a binary signal. By using a digital signal sequence as a carrier wave for analog coding, a cyanaloid signal and a digital signal can be transmitted simultaneously on the same line.
.

A detailed description of the invention is provided below with reference to the drawings.

11 Embodiment of the Invention FIG. 6 is a block diagram of a communication system according to an embodiment of the present invention. The input analog signal 20 (j(t)) is sent to the adder circuit 23
A constant amplitude value A0 generated by the DC generating circuit 22 is added to the constant amplitude value A0. On the other hand, the input digital signal 21 is converted by the code conversion circuit 24 into a two-company digital code sequence in which the maximum value of consecutive zeros is limited to a certain value, and is then converted to an analog signal with the above-mentioned constant amplitude value added by the multiplication circuit 25. The signal is multiplied and modulated and sent to the transmission line 26. (The code conversion circuit 24 and the code conversion circuit 32 on the receiving side, which will be described later, are connected to nine, for example, Kato, Nakayo, Ito: "On Transmission Line Code Formation of High-Speed Digital Optical Transmission System," Transactions of the Institute of Electronics and Communication Engineers, 1981. Year 1
February Va1.164-E, Na, 12. p, 146
9/1470) The received signal is line-equalized by a line equalization amount 27, and the analog signal extraction circuit 28 (for example, S, Stein.

(Co-authored by J. J. Jones, complete translation by Hideo Seki: Modern Communication Perspective Theory; pp. 190-194, Morikita Publishing, October 1970), the analog signal is extracted and an output analog signal 55 is obtained. On the other hand, the digital signal is subjected to multi-waveform shaping according to the amount of distortion 29, and is divided into m groups by the identification circuit 50 using the evening and first wave waves generated by the timing extraction circuit 51 and reproduced. A code conversion circuit 52 performs an inverse code conversion of the code conversion that limits the maximum value of consecutive zeros on the digital signal sequence of 900. , an output digital signal 34 is obtained. In FIG. 6, 35, 36, 37, 38, and 39.40 are output terminals, respectively.

Figure 4 (6), (6), (power and #) indicate the operating waveforms at each output terminal of the communication system of the present invention shown in Figure 6.Figure 4-) The analog signal waveform j(t)+j is obtained by adding a constant amplitude value A to the input analog signal A(t) at the output terminal 35. FIG. Maximum value is limited to a certain value 2
Value digital signal waveform. Figure 4 ((+) is the analog signal waveform of Figure 4 (-) at the output terminal 57.
) is a waveform obtained by multiplying and modulating the binary digital signal waveform. FIG. 4 shows the analog signal waveform extracted on the receiving side at the output terminal 58. FIG. 4 (-) shows the waveform of the 92-value digital signal which is identified and reproduced on the receiving side at the output terminal 69.

In this way, a constant amplitude value A is applied to the input analog signal Act).
Add 0 and multiply by a binary digital signal sequence j! Since it is modulated, even when the human input analog signal Act> is zero, when the binary digital signal tF1g is -1'', the pulse amplitude value can be secured as Ao, so it is possible to transmit the binary digital signal. Also, the maximum value N of a binary digital signal sequence U of consecutive zeros used as a carrier wave of an analog signal.
is guaranteed, so for a binary digital signal sequence,
If the clock network period is 10 seconds, at least (N+1
) There is always '1' within the period of T0 seconds. Therefore, according to the sampling theorem, at least /,, = 1/ l 2 (jV+ 1 ) T61
It is possible to transmit an analog signal having a frequency band of CHx).

FIG. 5 shows an example of the equalized waveform at the output terminal 40 shown in FIG. The analog signals (p,
α) and a digital signal (binary) are respectively divided. Therefore, by grading the characteristics of the line width conversion while observing the eye diagram, it is possible to optimally adjust the equalization waveforms of the analog signal series and digital signal series at the same time. .

Further, since the digital signal sequence is guaranteed to have a maximum value of consecutive zeros, it is possible to prevent the timing wave from disappearing. Therefore, it becomes possible to convert the transmission path to BSI (Bit Saqma*eg I*dapa turtle-devhea) without imposing any restrictions on the input digital signal.

In addition to the unidirectional transmission shown in FIG.
Analog and digital signals can be transmitted bidirectionally on the same transmission line.

DETAILED DESCRIPTION OF THE INVENTION As described above, the communication system of the present invention uses a digital signal as a carrier wave for an analog signal, which is different from the conventional method. . −
180% side stripe Eka. Hey there, a.

Since there is no need to perform nine-frequency multiplexing or DC component suppression using a device, it has the advantage that waveform deterioration is small, equipment adjustment is easy, and analog and digital signals can be transmitted simultaneously with high efficiency. It is highly effective.

[Brief Description of the Drawings] Figures 1 and 2 are block diagrams and used frequency bands of a conventional simultaneous transmission system for analog and digital signals using frequency division multiplexing, and Figures 3 and 4 (- to (e) Id A block diagram of an embodiment of the communication system according to the present invention and its operating waveforms. Fig. 5 is an eye diagram of the equalized waveform according to the present invention. 1.20...Input analog signal, 2.21-... Input digital signal, 6... DC component suppression code conversion circuit, 4
, 7... Duplexer, 5, 26... Transmission line, 6.27
--- Line equalizer, 8.29 --- Waveform equalizer, 9.5
0--identification circuit, 10--DC component suppression inverse code conversion circuit, 11.31--timing extraction circuit, 12.55
. . . Output analog signal, 13. 34 . . . . Multiplication circuit, 28 .
．． 59, 40...output terminal, Fα...analog signal band, Ft-...digital signal band, Sm, 5t=power spectrum of the analog signal and digital signal at the output terminal of the line equalizer 6. Patent applicant Nippon Telegraph and Telephone Public Corporation agent Patent attorney Gobe Tamamushi (6 others) No. 20 No. 50 Figure 4 n

Claims (1)

[Claims] In a communication system that transmits two signals, an analog signal and a digital signal, the transmitting side adds a certain amplitude value to the input analog signal, while converting the input digital signal into a digital signal series with a limited maximum number of consecutive signals. The analog signal obtained by adding the constant amplitude value is multiplied by 1 and modulated into the digital signal in which the maximum value of consecutive zeros is limited to a constant value, and then transmitted.The receiving side equalizes the received signal and creates the equalized waveform. a code that separates the signal into an analog signal and a digital signal in the amplitude axis direction, restores the separated analog signal to the input analog signal, identifies the separated digital signal, and limits the maximum value of the series of zeros to a constant value. A communication method characterized by performing an inverse transformation of the conversion and converting it to the input digital code.