JPS5828938B2 - Multi-drop signal transmission method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multi-drop signal transmission system in which a high-voltage power distribution line is used as a transmission path and a plurality of reception points are set at different transmission distances from a transmission point.

In a control system using high-voltage power distribution lines, a plurality of receiving devices are connected to one high-voltage power distribution line used as a transmission line.

Therefore, the input impedance of each receiving device must be set sufficiently high so as not to cause a heavy load at the signal frequency.

Incidentally, lines generally must be terminated with characteristic impedance to prevent signal standing waves from occurring, but unlike dedicated communication lines, this is difficult on power distribution lines.

Therefore, when a distribution line is used as a transmission path, under no load or near-no-load conditions, the terminal impedance becomes larger than the characteristic impedance, so the voltage level of the signal becomes high at the end of the line due to standing waves, and There is a point where the voltage level of the signal reaches a valley.

For example, as shown in FIG.
The transmitting device 2 is connected to the transmitting point S, and the receiving device 3a is connected to the receiving points R1r and R2 separated from the transmitting point S by different distances.

3b is connected.

At this time, the high-voltage distribution line 1 has, between the transmission point S and the termination,
As shown in FIG. 2, a standing wave is generated at the signal frequency.

If Vr is the signal level at the termination, the S/N ratio is naturally small at the point where the signal level is at the bottom, making it difficult to detect the signal.In general, the signal level Vs is taken as the threshold level, and the diagonal line in the diagram indicates the signal level. Reception in the indicated area is considered inappropriate.

Therefore, if the receiving device 3a is connected to the receiving point R1, either increase the transmission level or
Countermeasures must be taken, such as reconnecting the line to the receiving point R3, or connecting the terminal end to an impedance equal to the characteristic impedance of the line.

However, in both cases, the extension of high-voltage distribution lines,
Signal level distribution may change due to changes in track configuration, such as shortening, system changes, or separation of faulty sections.

In such a case, as shown in FIG. 3, the optimal reception point before the change, for example R3, becomes a position unsuitable for reception after the change.

The present invention has been made to improve the above points,
An arbitrarily selected receiving point can always be maintained at a good signal level regardless of changes in the configuration of the high-voltage distribution line, and S/
The present invention provides a multi-drop signal transmission system that can perform stable signal transmission with a high N.

The present invention has a signal of a first frequency and a frequency that is an even number multiple of this signal, and the phase is set so that the signal level peaks at a point where the signal level peaks due to the standing wave action of the above-mentioned signal. A transmitting device is connected to the transmission point, and generates a second frequency signal, modulates each signal with a control input, and sends the signal to the high-voltage power distribution line. The above object is achieved by connecting to the receiving point a receiving device which separately extracts the signals of the first and second frequencies using a filter circuit and then detects the signals and reproduces the control input.

When a signal of frequency f1 is transmitted through a line with no load at the end and a negligible attenuation constant, the signal level (11) at a distance l from the end is the bell, λ1 is the wavelength, and β1 is the phase constant.

The above signal level 11 is shown as a function of the distance l as shown in Fig. 4, and the signal level v11 of the standing wave due to the signal f1 is equal to the signal level of the signal f2 which has twice the frequency of the signal f1. The mountain of the level is opposed to the valley.

Therefore, when transmitting the same information, frequencies f1 and β2 (, -2nft
) signals (carrier waves), it is possible to detect information with a high S/N ratio from any single signal at an arbitrarily selected reception point.

Note that due to the difference in line impedance at the signal injection point (transmission point), the matching loss with the signal injection coupler differs between frequencies f1 and β2.

Also, due to the frequency characteristics of the power distribution equipment on the line, the signal levels at the terminal of both frequency f1 and β2 signals ■r1 and Vr
2 is generally not equal.

However, these differences are small compared to the level difference between the peaks and valleys of the signal level due to the standing wave ratio of each frequency. This allows the entire line to have a good reception level.

The present invention will be explained in detail below.

FIG. 5 is a schematic diagram showing an embodiment of the present invention.

In the figure, reference numeral 4 denotes a transmitting device, which is connected to a transmitting point S on the high-voltage distribution line 1.

5 is one of the receiving devices, and is connected to a receiving point H separated from the transmitting point S by an arbitrary distance.

The transmitting device 4 includes an oscillator 41 that generates a signal of frequency f1.
and an oscillator 4 that generates a signal of frequency f2 (-2f1).
2 and, in response to control input A, signal f1. Modulators 43 and 44 that simultaneously intermittent f2 and an amplifier 4 that amplifies the modulated output.
5.46 and a coupler 47 for injection into the distribution line 1 from the output transmission point S of the amplifier 45.46.

Note that these amplifiers 45, 46 and coupler 47 are
Configures an output circuit for high-voltage distribution lines.

The receiving device 5 includes a coupler 51 that is coupled to the distribution line 1 and blocks commercial frequency voltage, a filter 52.53 that extracts only the signals f, , β2, and detects the output of the filter 52.53 and thresholds the output. A detector 54.5 for regenerating said control input A by comparing the levels
5 and an OR circuit 5 that combines the outputs of both detectors 54 and 55.
It consists of 6.

From the transmitter 4 having the above configuration, a signal f7.modulated with the control signal A is sent. f2 is transmitted simultaneously.

Therefore, the receiving device 5 connected to the receiving point R simultaneously receives the signal f1. Receive f2.

By the way, the signal f1. As shown in Fig. 6, the level of f2 changes depending on the distance l, but f2=
2fl, the valley of the level of the signal ft coincides with the peak of the level of the signal f2.

Therefore, if the threshold level Vs is set as shown in the figure, the reception level at any reception point R exceeds the threshold level for at least one of the signals f1 and f2.

Therefore, the control signal can be extracted from the output of the OR circuit 56 with a good S/N ratio.

As described above, according to the present invention, any receiving point can be selected without any restrictions.

Moreover, as shown in FIG. 7, even if the absolute positions of the peaks and valleys of the signal level of each station wave number change on the line as a result of the system change, the two signals f1. Since the relative relationship between peaks and valleys at f2 does not change, at least one signal level exceeds the threshold level over the entire line even after the system change.

Therefore, according to the present invention, there is no need to reconfigure the communication system even if there is a change in the form of the high-voltage distribution line.

Note that the present invention is not limited to the above embodiment.

For example, amplifiers 45 and 46 in FIG. The amplification efficiency may be improved by using an f2 tuned progressive amplifier.

Further, the transmitting device and the receiving device may be configured as shown in FIG. 8 and FIG. 9, respectively.

That is, the transmitter includes an oscillator circuit including an oscillator 61, a frequency dividing circuit 62, and a switch SW1.

This oscillation circuit divides a second frequency signal f2 generated by an oscillator 61 by two in a frequency dividing circuit 62 to create a first frequency signal f1, and combines this first frequency signal and the above The signal of the second frequency from the oscillator 61 is outputted alternately by being switched at regular intervals with the switch SW1.

Then, the transmitting device modulates the signal output from the oscillation circuit by the control human power A in the converter 63, and then sends it to the high-voltage distribution line 1 through an output circuit consisting of an amplifier 64 and a coupler 65.

On the other hand, in the receiving device, the output of the transmitting device introduced through the coupler 51 is extracted separately for each of the first and second frequencies by filters 52 and 53, and is guided to the detection circuit.

The detection circuit includes a switch SW2, a detector 71, and a holding circuit 72.
The outputs of each of the filters 52 and 53 are switched at a constant switching cycle by the switch SW2, and the outputs of the filters 52 and 53 are alternately sent to the detector 7.
1, the detector 71 detects the signal, and outputs a signal only when the signal exceeds a predetermined threshold level.
After that, the level of this output is changed to a holding circuit 72 consisting of a retriggerable monostable multi-by-break (mono-multi).
The signal is held for at least half the switching period of the switch SW2 and output as a regenerated control signal.

Here, each switching period of the switching device SW1 and switching device SW2 is set to be shorter than the length of the control input A, and the switching period of the switching device SW1 is extremely shorter than the switching period of the switching device SW2. It is set.

With such a configuration, the switch SW0 is switched as shown in FIG. 10 to output the first and second frequency signals f.
1. f2 and send these signals to control input A (10th
When modulated as shown in Figure a), the transmitter sends out modulated outputs as shown in Figures c and d.

Here, Figure C shows the modulated output of the signal of the first frequency, and Figure d shows the modulated output of the signal of the second frequency.

First, each of these modulated outputs is extracted by filters 52 and 53 of the receiving device, and supplied to a detection circuit to reproduce the control power A.

By the way, if the signal level of the first frequency at the receiving point of the high voltage consideration line drops significantly, the signal level of the first frequency extracted by the filter 52 of the receiving device becomes extremely small.

Therefore, when the switch SW2 is switched as shown in FIG. 10e, the detector 71 receives a signal (FIG. ) is output.

If the output of this detector 71 is used as a reproduction output, it will be significantly different from the control input (FIG. 10a), resulting in incorrect reproduction.

However, in the device of this embodiment, the output of the detector 71 is introduced into the holding circuit 72, and the output level (u Hsr
level).

That is, the output of the detector 71 is held even during a period when the signal f1 of the first frequency cannot be detected by the retriggerable monostable multi-by-break of the holding circuit 72.

Therefore, the output of the holding circuit 72 becomes continuous, as shown in FIG. 10g, corresponding to the control input (FIG. 10a).

Note that the output of the holding circuit 72 is longer than the control input by approximately the holding period; however, if the switching period of the switch SW2 is set to be somewhat shorter than the length of the control input, this problem will not arise in practice. There isn't.

Furthermore, even if the signal level of the second frequency signal f2 drops significantly, the detection output of the signal that can be received at a high level is maintained, as in the case where the first frequency signal f1 drops. By doing so, the control human power A can be regenerated.

Thus, with the configuration of this embodiment, the switch SW1. S
Even though the signals of each frequency are switched at W2, accurate and highly reliable signal transmission can be performed.

Moreover, in this case as well, since either one of the first frequency signal and the second frequency signal can always be received and detected at a high level, signal transmission does not become impossible at all.

In addition, in this embodiment, the switch SW1. Since SW2 is used, only one system of oscillation circuit and detection circuit is required, which has the advantage of simplifying the configuration.

Moreover, signals ft, f of different frequencies are on the high-voltage distribution line 1.
2 do not exist at the same time, no interference waves are generated.

[Brief explanation of drawings]

Fig. 1 is a schematic system diagram showing a conventional multi-drop signal transmission system, Figs. 2 and 3 are characteristic diagrams showing signal levels before and after the system change in Fig. 1, and Fig. 4 is a detailed explanation of the present invention. FIG. 5 is a configuration diagram showing an embodiment of the present invention. FIGS. 6 and 7 are characteristic diagrams showing signal levels before and after the system change in FIG. FIG. 8 is a block diagram showing another example of the transmitting device, FIG. 9 is a block diagram showing another example of the receiving device, and FIG. Timing diagram for use. 1... High voltage distribution line, 4... Transmitting device,
5... Receiving device, 4L42, 61...
Oscillator, 43°44.63...Modulator, 45,
46.64...Amplifier, 47,5L65...
...Coupler, 52.53...Filter, 54
, 55, 71...detector, 56...OR circuit, SWl, SW2...switcher.

Claims (1)

[Claims] 1. In a signal transmission system in which a high-voltage distribution line is used as a transmission path and a plurality of reception points are set at different transmission distances from a transmission point, a signal of a first frequency and a frequency of an even multiple of this signal are used. an oscillation circuit that generates signals at second frequencies each having a frequency of A transmitting device consisting of an output circuit that sends out to the high voltage distribution line is connected to the transmission point, and an input circuit that introduces the modulated output sent out from the transmitting device from the high voltage distribution line, and a a filter circuit that extracts modulated outputs separately for each of the first frequency signal and the second frequency signal; and a detection circuit that detects the outputs of the filter circuits and outputs at least one of the detected outputs as the control human power. A multi-drop signal transmission system characterized in that a receiving device comprising: is connected to the receiving point, thereby transmitting a signal from the transmitting device to the receiving device. 2. The multi-drop signal according to claim 1, wherein the oscillating circuit of the transmitting device divides the output of an oscillator that oscillates at a second frequency using a frequency dividing circuit to obtain a signal at the first frequency. Transmission method. 3 The output circuit of the transmitting device converts the modulated output of the modulating circuit into the first
2. The multi-drop signal transmission system according to claim 1, wherein each signal of the second frequency is amplified by a tunable amplifier corresponding to that frequency and then transmitted.