JPH01319340A - Multiplexing transmission system - Google Patents

Abstract

PURPOSE:To miniaturize an instrument and to reduce cost by applying chirp conversion to a transmission signal to be multiplexed with a different conversion characteristic, adding the results to multiplex the signals and using the inverse conversion means of the chirp conversion at the reception side so as to demultiplex the multiplexing signal. CONSTITUTION:The inverse characteristic of chirp conversion elements 3, 5, 7 at the sender side is set to chirp conversion elements 14, 16 18 to demultiplex the multiplexed signals in channels 1-n. Since each demultiplexed signal component is the same as the input signal to the chirp conversion elements 3, 5, 7 at the sender side, the signal is inputted to a detection section 20 (n-set) by the synchronizing detection system or the like, the high frequency component (carrier) is eliminated therefrom, given to a digital signal conversion section 21 of digital signal conversion sections 21 (n-set), where the signal is converted into a digital pulse signal with a prescribed pulse waveform and an n-channel demodulation output is obtained. Since the conversion circuit for the chirp conversion is very simple, the multiplexers and demultiplexers are formed simply, inexpensively in small size and light weight.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a multiplex transmission method, particularly a multiplex transmission method in which input signals of multiple channels are multiplexed and transmitted using a common transmission path, and the signals are separated on the receiving side. Method % Formula % [Conventional technology] Conventional methods for multiplexing signal transmission include frequency multiplexing,
Methods such as time division multiplexing and wavelength multiplexing are used.

Frequency multiplexing is a method of multiplexing signals modulated with a certain occupied bandwidth by arranging them on the frequency axis at frequency intervals that do not overlap, and time division multiplexing is a method in which signals modulated with a certain occupied bandwidth are multiplexed by arranging them on the frequency axis at frequency intervals that do not overlap. It is a method of multiplexing multiple digital signals as a pulse train arranged at regular time intervals on the time axis.Wavelength multiplexing is also performed in optical communications, in which information is placed on light of different wavelengths, and the light is Multiplexing is performed by sending the signals over the same transmission path.

[Problems to be Solved by the Invention] The various multiplex transmission methods described above are selected depending on the contents and specifications of the system to be constructed. However, the above-mentioned conventional multiplex transmission system requires advanced technology for multiplexing signals and demultiplexing multiplexed signals, has a complicated configuration, and requires a large number of multiplexers.

There was a problem that the separation device was large and expensive.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a system that can be implemented simply and inexpensively, and that a multiplexing device and demultiplexing device can be constructed in a small size and at low cost.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides multiplex transmission in which input signals of multiple channels are multiplexed using a common transmission path and the signals are separated on the receiving side. In this method, on the transmitting side, each input signal is chirp-transformed using different chirp conversion characteristics for each channel, and then added and output to a common transmission path, while on the receiving side, the chirp conversion characteristics are inverse to the chirp conversion characteristics of each channel on the transmitting side. We adopted a configuration in which each signal is separated by chirp conversion using the chirp conversion characteristics of , and the signals of each channel are reproduced.

[Operation] According to the above configuration, signals are multiplexed by subjecting the transmission signals to be multiplexed to chirp transform using different conversion characteristics and adding them, while on the receiving side, multiplexing is performed by the inverse conversion means of the chirp transform described above. separation of signals can be performed.

[Example] The present invention will be described in detail below based on an example shown in one drawing.

1 and 2 show an embodiment of the invention. FIG. 1 shows the configuration of the transmitting device, and FIG. 2 shows the configuration of the receiving device.

In FIG. 1, reference numeral 1 denotes n pulse generators (for n channels), which convert digital signals of input serial pulses into pulse signals. The output pulse signals of this pulse generator 1 are similarly input to n balanced modulation sections 2, where the pulse signals are amplitude-modulated by superimposing a high frequency signal (carrier wave). Therefore, the output cassette vector of the balanced modulator 2 has harmonic components corresponding to the input pulse signal waveform from the pulse generator 1, centered on the carrier wave.

The outputs (n pieces) of the balanced modulation section 2 are chirp conversion elements 3.5
．． 7 (n pieces) and undergoes chirp conversion. As is well known, the chirp conversion element 3.5.7 disperses (expands) the spectrum of the input signal on the time axis. For example, it reduces the amount of delay on the low frequency component side and reduces the amount of delay on the high frequency side. If the increased delay characteristic is used, the spectrum of the input signal will be expanded on the time axis.

Furthermore, the chirp conversion element 3.5.7 has a code of 4.6.8.
They have different delay characteristics as follows. Code 4.6.8
The horizontal axis of the graph section shows the delay time, and the vertical axis shows the frequency.As is clear from this figure, the chirp conversion element 3.5
In this case, the delay is small on the low frequency side, and the delay is large on the high frequency side.

Furthermore, in the chirp conversion element 3.5, as can be seen from the slope of the straight line, the rate of change in delay with respect to frequency is different. Furthermore, in the chirp conversion element 7, the delay is large on the low frequency side, and the delay is small on the high frequency side.

In this way, if different delay characteristics are used for the chirp conversion elements 3.5.7, even if the outputs of the chirp conversion elements 3.5.7 are added by the adder 9, the receiving side will have delay characteristics with opposite characteristics. It should be possible to separate the signals using the chirp conversion element that has it.

The output of the adder 9 is input to an amplifier lO and used to drive a suitable transmitter, for example an E10 converter 11. E
10 The conversion unit 11 is configured using a semiconductor laser element, etc., converts the multiplexed signal by chirp conversion into an optical signal, and outputs it to the air or to a transmission path such as an optical fiber.

On the other hand, in the receiving device shown in FIG. 2, reference numeral 12 denotes an optical/electrical converter (0/E converter) that converts an optical signal input from the transmitter into an electrical signal using a photodiode or the like;
Reference numeral 13 is an amplification section that amplifies the electrical signal obtained by the O/E conversion section 12, and this #! The output of the one-width section 13 is input to the chirp conversion element l4.16.18.

The chirp conversion elements 14, 16, and 18 are basically the same as the chirp conversion elements 3 and 5.7, and the graph portion 15.
17.19, the chirp conversion elements 3.5.
It has conversion characteristics opposite to 7.

In this way, by setting the inverse characteristics of the chirp conversion element 3.5.7 on the transmitting side to the chirp conversion element 14.16.18, the signals of multiplexed channels 1-=n are separated. Each signal component is the same as the input signal to the chirp conversion element 3.5.7 on the transmitting side, so it is input to the detection section 20 (n pieces) using a synchronous detection method etc., and the high frequency component (carrier wave) is removed. Thereafter, the signals are input to the digital signal converters 21 of the digital signal converters 21 (n pieces), and are converted into digital pulse signals having a predetermined pulse waveform, thereby obtaining demodulated outputs for n channels.

Chirp conversion element 3.5, 7 and chirp conversion element 1
The simplest characteristics of 4.16.18 are 5AW-D
A configuration using DL (surface acoustic wave delay line) can be considered. FIGS. 3(L) to 3(e) show a configuration example of the chirp conversion element 3 among the chirp conversion elements on the transmitting side and the receiving side.

The chirp conversion element 3 has a structure in which comb-shaped electrodes (hereinafter referred to as IDT) 33a and 33b are arranged on a piezoelectric substrate 33c having a piezoelectric effect, as shown in FIG. 2 (IL),
When an electric signal is applied to the IDT 33a of the signal input section, mechanical vibration is generated due to the piezoelectric effect, and a surface wave of the vibration propagates on the substrate 33c.

When this surface wave reaches the IDT 33b of the output section, it is converted into an electric signal again. The output IDT 33b generates an electrical signal in tune with the vibration frequency determined by the electrode spacing, but as shown in the figure, the spacing between the output IDTs 33a changes more closely as the distance from the input IDT 33b increases, so the output signal is delayed depending on the frequency. Time is different.

That is, different frequency components in the signal are separated in time. The output amplitude and delay characteristics with respect to the input frequency of this expansion chirp conversion element are shown in wS3 (b) and (C).
), that is, at least the frequency f
The frequency characteristic is flat in the region from 1 to fki, while the delay time increases linearly (tl to t2) from frequency fl to f2 due to the electrode arrangement described above.
The characteristics in Figure (c) are the same as those in graph section 4 in Figure 1).

Therefore, when a pulse-like signal as shown in FIG. 3(d) containing a high frequency component having a spectrum component spread between fl and f2 is input to the expansion chirp conversion element 3, as shown in FIG.
e), the frequency is fl during the time interval 11 to t2.
The signal is expanded into a waveform (chirp signal) that continuously changes from f2 to f2 and is output.

Next, the operation in the above configuration will be explained.

In the transmitting section of FIG. 1, each of n input terminals has n
The digital signal of the channel is input. These digital input signals are converted into pulse signals of appropriate width in a pulse generator 1, and furthermore, a high frequency signal is superimposed on this pulse signal in a balanced modulation section 2.

The signal is input to the chirp conversion element 3 having the characteristics of the graph section 4.6.8, and is converted into a chirp signal.

At this time, the n-channel modulated signals are input to the chirp conversion elements 3, 7, and 7, which all have different delay dispersion characteristics, as shown in graph section 4.6.8.
Chirp signals whose frequency components are distributed in different ways on the time axis are obtained as outputs.

The n different chirp signals obtained here are combined into one signal by the adder 9, and amplified by the amplifier 10 to an appropriate level.

The multiplexed electrical signals are then converted into optical signals in the E10 converter 11 and transmitted.

On the other hand, the optical signal transmitted from the transmitting section in the receiving section of FIG.

This amplified signal is transmitted to different graph sections 15 and 15.
．． 14.16.1 Chirp conversion element with 17.19
8 is input. This chirp conversion element 14.
16.18, the desired signal is separated and compressed, and a pulse signal containing high frequency components is output.

The signal input at this time includes chirp signals of each channel, but separating and compressing a desired chirp signal from among the chirp signals is performed by the chirp conversion element 3.5 of the transmitting device.
．． Chirp conversion element 14.1 with conversion characteristics opposite to 7.
By using 6.18, signals of desired channels can be separated. Since the chirp conversion element 14, 16, 18 responds only to the chirp signal corresponding to its conversion characteristic,
Only desired channel signals can be reliably separated.

The amplitude-modulated signals separated by the chirp conversion elements 14, 16, and 18 are input to the detection section 20 and converted into pulse signals containing no high frequency components, and then the pulse signals are converted into digital signals in the digital signal conversion section 21. Convert and output.

According to the above configuration, the signals of the channels to be transmitted are converted into chirp signals using different chirp conversion characteristics, and the signals are added together and transmitted, while the receiving side performs chirp conversion for each channel with the opposite characteristics to that of the transmitting side. By doing this, the signal of the target channel can be separated. As shown in FIG. 3, the chirp conversion element can be constructed easily, inexpensively, and compactly, so it has the advantage that the multiplexer and demultiplexer can be constructed significantly simpler, cheaper, smaller, and lighter than conventional multiplexing systems.

In addition, as in the above embodiment, by applying this method to optical space transmission or transmission using optical fibers, the effects of signal attenuation and fluctuations on the transmission path are improved, and the quality of the transmission path is improved. It has the effect of especially,
In chirp transformation during demodulation, the waveform shown in Fig. 3(e) is compressed in the time axis direction to form the waveform shown in Fig. 3(d), but the component compressed in this way has predetermined characteristics. This has the advantage that the element does not respond to noise components and is therefore less susceptible to the effects of external noise.

The conversion gain on the receiving side is determined by the chirp signal duration T (t1 to t2 in Figure 3 (e)) and the bandwidth B (
It can be evaluated by the product (BT product) of f1 to f2 in FIG. 3(b). In conversion from a chirp signal, 1normal BT product is l
Since the signal is converted into a pulse signal with a peak power BT and a pulse width 1/B, which is much larger than , the S/N ratio is improved, and even when only weak signals can be received, signal reproduction is possible reliably.

Further, since communication cannot be performed unless the chirp conversion characteristics are correct/reverse on the transmitting and receiving sides, there is an advantage that communication is highly confidential.

In the above embodiment, the case where the input signal is a digital signal is shown, but the chirp conversion element is a delay line with different delay times depending on the frequency, and if the signal has multiple frequency components, it is converted into a chirp signal with different conversion characteristics. You can perform the conversion (or inverse conversion) of Therefore, it can also be used for FM modulated waves.

For example, by adopting a configuration as shown in FIG. 4, multiplex transmission of FM modulated waves is also possible. In this case, the input signal can be an analog signal or a digital signal.

Reference numeral 22 in FIG. 4 (&) is an n-channel FM modulation section, and this FM modulation section 22 performs FM modulation on the input signal (analog or digital) and inputs it to the chirp conversion element 3.5.7. The structure after chirp conversion element 3.5 and 7 is the first
Similar to the figure, the signal chirp-converted by the chirp conversion element 3.5.7 is added in the adder 9, and the amplification unit 1O1E
10 and optically transmitted via the converter 11.

On the other hand, FIG. 4(b) shows the structure of the receiving device, which differs from FIG. 2 in that FM demodulators 23 for n channels are connected to the rear stages of the chirp conversion elements 14, 16, and 18, respectively. .

With such a configuration, the chirp conversion element 14.16.1
Since the signal separated in step 8 is the same as the FM modulated wave input to chirp conversion element 3.5.7, FM demodulation section 2
By demodulating these signals using 3, it is possible to separate and demodulate the n-channel transmission signals.

Furthermore, although optical transmission was used as an example in the above embodiment, the signal transmission method itself is not limited to this, and various transmission methods such as wireless transmission using electromagnetic waves, various wired transmissions, and other methods may be used depending on the configuration of the transmission path. Needless to say, you can use it.

[Effects of the Invention] As is clear from the above, according to the present invention, in a multiplex transmission system in which input signals of a plurality of channels are multiplexed using a common transmission path and the signals are separated on the receiving side, On the receiving side, each input signal is chirp-transformed using different chirp conversion characteristics for each channel, and then added and output to a common transmission path.On the other hand, on the receiving side, the chirp conversion characteristics are reversed to the chirp conversion characteristics of each channel on the transmitting side. Since it uses a configuration in which each signal is separated by chirp conversion and the signal of each channel is regenerated, the signals to be multiplexed are multiplexed by performing chirp conversion on each transmission signal to be multiplexed using different conversion characteristics and adding them. On the receiving side, on the other hand, the multiplexed signal can be separated by the inverse transformation means of the chirp transformation described above. In particular, chirp conversion has the advantage that the conversion circuit is very simple, so that the multiplexer and demultiplexer can be constructed extremely simply, inexpensively, compactly and lightweight. In addition, since the signals of each channel are chirp-converted, there are excellent advantages such as improved S/N ratio, improved communication reliability, and improved confidentiality.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a transmitting device adopting the present invention, and FIG.
The figure is a block diagram of a receiving device used together with the transmitting device of FIG. FIG. 2 is a block diagram showing the configurations of a transmitting device and a receiving device, which are different from each other. 1... Pulse signal converter 2... Balanced modulator 3.5.7.14, te, to... Chirp conversion element 9... Adder lO... Amplifier 11...
- E10 conversion section 12... O/E conversion section 13... Amplification section 20... Detection section 21... Digital signal conversion section 22... FM modulation section 23... FM demodulation section 33
a, 33 b・-I DT 33c... Board straw 1 figure d Uke 1chi

Claims (1)

[Claims] 1) In a multiplex transmission method in which input signals of a plurality of channels are multiplexed using a common transmission path and the signals are separated on the receiving side, on the transmitting side, each input signal is sent separately for each channel. After performing chirp conversion using different chirp conversion characteristics, the signals are added together and output to a common transmission path.On the other hand, on the receiving side, each signal is separated by chirp conversion using chirp conversion characteristics that are opposite to the chirp conversion characteristics of each channel on the transmitting side. A multiplex transmission method characterized by regenerating channel signals. 2) The multiplex transmission system according to claim 1, wherein each of the chirp transformations on the transmitting and receiving sides is performed using a surface acoustic wave dispersion type delay line.