JPS63182921A - Power line carrier communication equipment - Google Patents

Abstract

PURPOSE:To simplify the error detection by providing a means using two different frequencies to apply frequency modulation to a serial data, sending the result to a power line and a means receiving two sent modulation signals respectively and demodulating the result into a serial data and a means detecting the noncoincidence of two demodulated serial data. CONSTITUTION:Power line carrier communication transmission circuits 3A, 3B have respectively a different carrier frequency. Similarly, in the power line carrier communication transmission circuits 5A, 5B, the tuning frequency differs from each other, the circuit 5A receives the transmission signal from the circuit 3A, and the circuit 5B receives the transmission signal from the circuit 3B. An exclusive OR circuit 20 detects the noncoincidence of the demodulated serial data by the circuits 5A, 5B. Moreover, a coding reception circuit 21 converting the serial data into the parallel data for display discriminates it as an error if an output is given from the exclusive OR 20 when the data is sampled at its center.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power line carrier communication device, and particularly to an improvement in detecting transmission errors due to noise.

[Conventional technology]

In order to transmit data captured by a sensor to a remote location, it is desirable to install transmission media such as twisted pair wires, coaxial cables, and optical fiber cables from the perspective of transmission quality. Because installation requires a great deal of cost and labor, it is difficult to transmit data in large numbers, such as when transmitting data from an elevator earthquake sensor to a display device in a hall or manager's room. If you don't have one, it may not be worth it from a cost perspective, and you may consider using a wireless method, but the distance and location between the sending and receiving sides! In some cases, it may not be possible to transmit data depending on the relationship, and it is also vulnerable to noise. Therefore, in such cases, power line carrier communication using power lines such as commercial power lines is applied.

The fifth example is a configuration of a conventional power line carrier communication device in which data and information are transmitted from a certain sensor to a display device.
Although shown in the figure, the invention is of course not limited to this example.

In FIG. 5, 1 is a sensor such as an earthquake sensor, 2 is an encoding transmission circuit that converts an analog signal from sensor 1 into serial data of a digital signal, and 3 is a frequency modulated serial data and transmits it to power line 4. a power line carrier communication transmitting circuit; 5 a power line carrier communication receiving circuit that demodulates the transmitted modulated signal into serial data; 6 a coding receiving circuit that converts the serial data into parallel data for display;
7 is a display device, and 8 is an error detection circuit that checks whether there are any errors in the sent data.

In the above configuration, first, the physical quantity captured by the sensor 1 is converted into a numerical value by the encoding transmitting circuit 2, frequency-modulated by the power line carrier communication transmitting circuit 3, and transmitted to the power line 4. The power line carrier communication receiving circuit 5 demodulates it into serial data, the encoding receiving circuit 6 converts it into display data, and the contents are displayed on the display tube N7. At this time, the error detection circuit 8
Now check if there are any errors in the data sent,
If there is an error, measures are taken such as not displaying the data.

Incidentally, errors in data are often caused by noise from the switching operations of various devices connected to the power line that gets on the power line, and Figures 6 and 7 show how such noise causes errors in data. This will be explained using figures.

FIG. 6 is a block diagram showing a power vAIIa transmission/communication receiving path receiving circuit, in which 10 is a tuning circuit, 11 is a frequency-voltage conversion circuit, 12 and 14 are comparators, 13 is an impulse noise filter, and 15 is a It is an integrating capacitor.

FIGS. 7(A) to 7(H) are diagrams showing the signal waveforms of each part in FIG. 6 and the influence of noise as time is plotted on the horizontal axis.

The signal transmitted to the power line 4 is sorted through a tuning circuit 10 and sent to a frequency-to-voltage conversion circuit 11.In the frequency-to-voltage conversion circuit 11, the deviation of the incoming signal from the carrier frequency is the output voltage. (Here, it is assumed that the voltage is converted to a positive voltage when it is lower than the carrier frequency, and to a negative voltage when it is higher than the carrier frequency.) The data is then compared by the comparator 12 and formatted into (1, 0) data. For example, if the transmitted data is as shown in FIG. 7(a), the output waveform of the comparator 12 in the absence of noise will be as shown in FIG. 7(b).

The output of comparator 12 is impulse noise filter 1
3 and charges and discharges the integrating capacitor 15. FIG. 7(c) shows the terminal voltage waveform of the integrating capacitor 15. The output of the impulse noise filter 13 is input to the comparator 14, and the output has a waveform shown in FIG. 7(d), which is output to the encoding/receiving circuit 6 as received data. Now, if impulse noise occurs on the power line 4 such that the output of the frequency-voltage conversion circuit is as shown in FIG. As a result, comparator 1
The output of step 4 is as shown in (h) of FIG. That is, among the impulse noises a y f in FIG. 7(e), only C and e ultimately affect the output in FIG. 7(h), causing pulse width jitter of ΔW or ΔW'.

In this way, a number of impulse noises are carried on the power line, and their influence appears as pulse width jitter to the left and right of the data change point when there is no noise. In other words, the effect of noise appears as a shift in the data change point, and the pulse width becomes wider (here, when the noise frequency is lower than the carrier frequency) or narrowed (here, when the noise frequency is higher than the carrier frequency). However, if the movement of this change point becomes large, errors will occur in the data.

[Problem that the invention seeks to solve]

As mentioned above, the problem of transmission errors is always present in data communication. Therefore, the configuration shown in FIG. Alternatively, methods such as triple transmission verification and cyclic redundancy check are well known. However, either method has the problem of requiring microcomputerization or complex logic, and as mentioned above, when the amount of data to be transmitted is small, it is desirable to be able to detect errors more easily.

[Means for solving problems]

The present invention has been made to solve the above problems,
The closer the noise frequency is to the carrier frequency, the greater the effect will be, and if it is far away, there will be little effect. Therefore, if the same data is transmitted using two different carrier frequencies, the noise will affect each data. Focusing on the fact that different signals have different effects, we developed a means for frequency modulating serial data at two different frequencies and transmitting it to the power line, and a means for receiving each of the two transmitted modulated signals and demodulating them into serial data. , is characterized in that it includes means for detecting a mismatch between two demodulated serial data.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a diagram showing an example of the configuration of a power line carrier communication device according to the present invention.

In FIG. 1, 3A and 3B correspond to the power line carrier communication transmitting circuit 3 of FIG. 5, but the power line carrier communication transmitting circuits 3A and 3B have different carrier frequencies. Similarly, 5A and 5B are the power vA* in FIG.
The frequency of the tuned circuit is different between 5A and 5B, and the power line carrier communication receiver circuit 5A receives the transmission from the power line carrier communication transmitter circuit 3A, and the power line carrier communication receiver circuit 5B receives the transmission from the power line carrier communication transmitter circuit 3A. Receives transmission from carrier communication transmission circuit 3B. Reference numeral 20 denotes an exclusive OR as means for detecting a mismatch between the serial data demodulated by the power line carrier communication receiving circuits 5A and 5B.

21 is an encoding/receiving circuit that converts serial data into parallel data for display; as described later, if there is an output from exclusive OR 20 when sampling at the center of the data, that data is determined to be incorrect. do.

In the above configuration, first, the influence of noise on each demodulated data when data is transmitted using two different carrier frequencies will be explained with reference to FIGS. 2 and 3.

FIG. 2 shows frequency spectra of data A and data B transmitted at different carrier frequencies and assumed noises N1 to N.

FIGS. 3(A) to 3(G) show the influence of noise N, to N, on received data, respectively.

First, looking at noise N1, this is noise with a frequency lower than the carrier frequency of data A and data B, and as explained in (e) to (h) of FIG. 7, the pulse width of II H11 of data is There is a tendency to widen the jitter (hereinafter referred to as upper jitter). However, the output shown in FIG. 7(e) is more likely to be produced as the noise frequency and carrier frequency get closer together, and hardly any more if they are far apart. Therefore, noise N+ tends to cause positive jitter near data A, but since it is far away from data B, it has almost no effect on data B, and as a result, the received data A is affected by the noise N1. and B are shown in Fig. 3 (A).

Similarly, in the case of noise N2, the frequency is lower than that of data A and B, but since it is close to data 8, there is a strong tendency to cause a positive shifter in data A, so that the received data A and B due to the influence of noise N2 are The result is as shown in Figure 3 (b).

In the case of noise N, the frequency is higher than data A, so the pulse width of data IT HIt is narrowed (hereinafter referred to as negative jitter) (it is in the lJl direction and is close to data A, so its influence is large; on the other hand, data Since it is still far away from B, there is little influence, so the received data A,
B is shown in Figure 3 (c) (about the same time).

Similarly, the influence of noise N4 is shown in Figure 3 (d).
A small negative shifter for data 8, as shown in
This tends to cause a small positive jitter with respect to data B, and the noises N and N are also as shown in FIGS. 3(E) to (G), respectively.

In this way, when one data is transmitted using different carrier frequencies, if there is noise, it will have different effects on each data and the demodulated received data will not match, making it easier to avoid errors. It becomes possible to detect.

This will be explained with reference to FIGS. 1 and 4.

The received data when there is no noise is shown in (a) in Fig. 4. When noise is present, the outputs of the power line carrier communication receiving circuits 5A and 5B have different jitters due to the influence of noise as described above. Therefore, the result will be as shown in (b) and (c) of FIG. 4, for example, and the output of the exclusive OR 20 at that time will be as shown in FIG. 4 (d).

As explained in Figure 3, when transmitting using different carrier frequencies, jitter rarely appears in the same way in each received data (the areas where the received data do not match are due to noise), so the exclusive OR The output of 20 is
The data is judged to be erroneous while the signal is showing lpa. As for the timing of this judgment, since jitter occurs to the left and right of the data change point when there is no noise, sampling is performed at the center of the data when there is no noise, and at that time the output of the exclusive OR 20 is The influence of jitter can be minimized by determining whether it exists or not.

Figure 4 (e) shows the sampling timing.
The encoder/receiver circuit 21 reads the received data at this sampling timing, and if the output of the exclusive OR is IT I IT, the data is determined to be erroneous as shown in (f) of FIG. . Note that this sampling timing can be easily created by using PLL or power supply synchronization.

If there is no erroneous bit in the center of the series of data, the encoding/receiving circuit 21 adopts that data and updates the display contents of the display device 7, and if there is an erroneous bit, it discards the data and leaves the display unchanged. do.

〔Effect of the invention〕

According to the present invention, the error detection hardware has a simple configuration, and reliability is thereby improved.

Furthermore, since it is not necessary to add redundant bits for error detection or to perform double or triple transmission, the baud rate can be reduced accordingly and the error rate can be reduced. Alternatively, even if the baud rate is the same, there is no need to send extra information for error detection, so more information can be sent, which is an excellent effect.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the configuration of a power line carrier communication device according to the present invention, FIG. 2 is a diagram showing frequency spectra of data and noise, and FIG. 3 is a diagram for explaining the influence of noise on data. FIG. 4 is a diagram for explaining error determination in received data, FIG. 5 is a diagram showing an example of the configuration of a conventional power line carrier communication device, and FIG. 6 is a block diagram showing a power vAill transmission/communication receiving/transmitting path receiving circuit. , FIG. 7 is a diagram for explaining the waveforms of each part of the power line carrier communication receiving circuit and the influence of noise. 1...Sensor 2...Encoding transmission circuit 3.3A, 3B...Power line carrier communication transmission circuit 4...
Power line 5.5A, 5B...Power line carrier communication receiving circuit 6.21
... Encoding reception circuit 7 ... Display device 8 ... Error detection circuit 20 ... Exclusive OR patent applicant Fujichik Co., Ltd. Figure 2 Figure 3 Figure 3

Claims (1)

[Claims] The output from the sensor is converted into serial data and transmitted to a remote location by power line carrier communication, comprising: means for frequency modulating the serial data with two different carrier frequencies and transmitting the same to the power line; What is claimed is: 1. A power line carrier communication device comprising means for receiving two received modulated signals and demodulating them into serial data, and means for detecting a mismatch between the two demodulated serial data.