JP2002261662A - Power line communication apparatus and method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power line communication apparatus allowing a stable communication even when impedance substantially varies in a power line or a noise is caused that varies with time. SOLUTION: The apparatus is configured such that test data outputted from a test data producing unit 1-2 is demodulation processed by a demodulating unit 1-1, a transmission signal outputted through a D/A converter 1-3 and an amplifier 1-4 is inputted to a demodulating unit 1-7 via a transformer 2-1 of a coupling circuit 2 and an A/D converter 1-6 for demodulation to reception data, a comparison is made between above reception data with the test data by a comparison correcting unit 1-5, correction data is acquired such that the received data equals the test data, and the transmission data is modulation processed using the correction data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission line using a power line as a transmission medium, and more particularly to a communication apparatus using a power line as a transmission medium and having a large impedance variation and noise interference.

[0002]

2. Description of the Related Art In recent years, with the spread of information devices such as personal computers and the improvement of information processing capabilities, the introduction of information networks typified by the Internet and private LAN has rapidly expanded to factories, buildings, and ordinary households. I have.
There is also a growing need to transmit large amounts of data such as images and sounds at high speed. Transmission media that make up such networks include dedicated lines, telephone lines, cable television (CATV) lines, wireless, and power lines. In particular, power lines are laid at extremely high densities inside and outside buildings, such as factories, buildings, and homes as users. By using the power lines as a communication medium, a communication network can be constructed without laying a new communication cable. . Also,
If the communication device is connected to an outlet installed at home or office, there is an advantage that a communication network can be easily constructed.

A power line communication device has a commercial power supply system (100
(Volts, 50 Hz or 60 Hz) and a signal processing system for communication are connected to a power line via a coupling means using an AC coupling element such as a transformer or a capacitor.

[0004] The impedance of the power line, which is the transmission line, is
The impedance of the power line varies greatly depending on the load on the power line, that is, the usage condition of the electric device by the user. When the impedance in the carrier frequency band is significantly reduced due to the impedance fluctuation, the signal level of the carrier wave is attenuated and the communication device may not be able to receive the signal. For this reason, coupling means for increasing the received signal level in the carrier frequency band is used.

Japanese Patent Application Laid-Open No. 2000-353991 discloses that the impedance of a power line is reduced during transmission by specifying the degree of coupling between a primary side and a secondary side of a transformer for separating a commercial power supply system and a communication signal processing system. This document describes power line communication in which the influence of power line impedance fluctuations is suppressed by increasing the level at the time of reception.

[0006]

As described above, in power line communication, various electric devices are connected as loads for each user, and the impedance varies depending on the time of use. In the above-mentioned known example, a method of specifying the degree of coupling of the transformer constituting the coupling means, that is, a method of responding to the impedance variation by a static method. However, as described above, the load of the user using the power line is various, and there is a limit to the impedance fluctuation width that can be handled by the static method. Further, in the future, there is a possibility that electrical equipment with unexpected load conditions may be developed and used.In the above-mentioned known example, the power line impedance at the time of reception cannot always be kept high, and the signal level required for communication cannot be obtained. It is possible that it cannot be done.

[0007] In recent years, since the number of electric devices equipped with an inverter, a switching power supply, and the like has increased, noise tends to be superimposed on a power line to which these devices are connected. The nature of these noises varies with the type of electrical equipment and the manufacturer. Usually, a filter is provided as a noise countermeasure, but when the difference between the communication signal level and the noise level is small at the communication frequency, the countermeasure is difficult because the communication signal is attenuated together with the noise.

In the above conventional example, no consideration is given to the superposition of noise. That is, in the power line, the impedance and the noise that fluctuate for each user and each time zone hinder communication.

The present invention has been made in view of the above points, and an object of the present invention is to provide stable communication even when a large impedance fluctuation occurs in a power line or noise that changes with time occurs. It is an object of the present invention to provide a power line communication device and a communication method for the same.

[0010]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides a communication apparatus comprising a modulator for outputting a transmission signal comprising a plurality of frequency components to a power line and a demodulator for inputting a reception signal from the power line. Or a communication method using the same, wherein (1) a test signal output from the modulator is input as a monitor signal to the demodulator, and a signal level is compared for each frequency component of the monitor signal and the test signal. Outputting a transmission signal whose signal level has been corrected so that the signal level of the monitor signal is equal to or higher than the signal level of the test signal for each frequency component, or (2) reducing the noise level of the communication frequency band superimposed on the power line. Measurement is performed for each frequency component, and a transmission signal whose ratio between the noise level and the transmission signal level is equal to or greater than a predetermined threshold value for each frequency component is transmitted to the modulation unit. And outputs.

That is, according to one aspect of the present invention, a power line having a modulator for outputting a transmission signal having a plurality of frequency components to a power line and a demodulator for inputting a received signal from the power line. A communication device, comprising: a test data generation unit that outputs test data having a predetermined signal level at each frequency component; and a test signal output from the modulation unit as test data as a transmission signal. A demodulation unit which inputs and demodulates the demodulated signal; and a comparison / correction unit which outputs correction data in which the level of the demodulated monitor signal and the signal level of the test data are equal to or higher than the level of each frequency component. The power line communication device is characterized in that the signal level is changed for each frequency component of the transmission signal based on the transmission signal and the transmission signal is output.

According to a second aspect, there is provided a power line communication apparatus having a modulation unit for outputting a transmission signal including a plurality of frequency components to a power line and a demodulation unit for inputting a reception signal from the power line. A noise level determination unit that measures the noise level for each frequency component and outputs correction data in which the transmission signal is equal to or higher than a predetermined predetermined level from the noise level at each frequency component, and is transmitted based on the correction data by the modulation unit. A power line communication device characterized in that a signal level is changed for each frequency component of a signal to output a transmission signal.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. The parts with the same numbers in each figure indicate the corresponding parts. FIG. 1 shows an embodiment of a communication device according to the present invention.

In FIG. 1, information devices 5a and 5b as transmission / reception sources of communication data are, for example, personal computers and network-compatible home electric appliances. Communication device 1
0a and the communication device 10b have the same configuration and function, so the details of the communication device 10b are omitted. The transmission data and the reception data of the information device 5a are transmitted and received on the power line 4 by the communication device 10a. Similarly, the transmission data and the reception data of the information device 5b are also transmitted by the communication device 10b to the power line 4.
Is transmitted and received. The communication device 10a includes a signal processing circuit 1 and a coupling circuit 2. A transmission signal obtained by subjecting transmission data from the information device 5b to signal processing by the signal processing circuit 1 is combined into a coupling circuit 2a.
To the power line 4 via the Power line 4 from coupling circuit 2
The transmission signal output to the information device 5b is received by the communication device 10b, and is input to the information device 5b as reception data via a coupling circuit (not shown) and a signal processing circuit (not shown). on the other hand,
The transmission data output from the information device 5b is output to the power line 4 via a signal processing circuit (not shown) and a coupling circuit (not shown). The transmission signal is received by the coupling circuit 2 of the communication device 10a, input as a reception signal by the signal processing circuit 1, processed by the signal processing, becomes reception data, and is received by the information equipment 5a. The power line 4 is connected to an electric device 6 having a frequency characteristic such that the power line impedance seen from the communication device 10a in a certain frequency band is reduced.
They are connected via 1, 6-2. Although FIG. 1 shows two communication devices and one electric device for easy understanding, the same applies to three or more communication devices and two or more electric devices.

Hereinafter, the communication device 10a will be specifically described. The communication device 10a includes a signal processing circuit 1 and a coupling circuit 2. First, the coupling circuit 2 will be described.
The coupling circuit 2 includes capacitors 2-2 and 2-3 connected to the power line 4 of the transformer 2-1 and the transformer 2-1 and a DC cut capacitor 2 connected to the signal processing circuit 1 of the transformer 2-1. -4. Capacitor 2-2,
2-3 functions as a filter that cuts off the commercial power frequency (50 Hz or 60 Hz) by the coil L1 of the transformer 2-1. The transformer 2-1 and the signal processing circuit 1
A connection is made so that a reception signal is output from a terminal 2-1-1 of the transformer 2-1 and a transmission signal is input to a terminal 2-1-2. The terminal 2-1-3 of the transformer 2-1 is grounded to the ground level.

The coils L1, L2, L3 of the transformer 2-1
Is determined by the levels of the transmission signal and the reception signal. For example, in order to double the transmission signal level and output it to the power line 4, the ratio of the turns of the coil L3 to the coil L1 is 1: 2, and to receive the reception signal level from the power line 4 at the same magnification, the coil L2 And the turn ratio of the sum of the coil L3 and the coil L1 is 1: 1. The transmission signal output from the signal processing circuit 1 propagates from the coils L3 to L1 of the transformer 2-1 of the coupling circuit 2 and is output to the power line 4, but at the same time, the coil L
1 also propagates to the coil L2. It can be considered that both ends of the coil L1 are connected to an impedance (referred to as a power line impedance) determined by the power line 4, the electric device 6, and the communication device 10b.

The power line impedance is determined by the communication device 10b.
Is designed to have a high value in the communication frequency band, the impedance is determined by the power line 4 and the electric device 6. Therefore, the transmission signal output from the signal processing circuit 1 also propagates to the coil L2 while being affected by the power line impedance when propagating from the coil L3 of the transformer 2-1 to the coil L1. That is, the signal processing circuit 1 can input, as a reception signal, a signal affected by the power line impedance in a transmission signal output by itself (hereinafter, a reception signal corresponding to its own output signal is referred to as a monitor signal). Naturally, the relationship between the level of the transmission signal and the level of the monitor signal in this case is determined by the power line impedance and the turns ratio of the coils L1, L2, L3.

Next, the signal processing circuit 1 will be described.
The signal processing circuit 1 is a digital signal processing circuit. When transmitting transmission data output from the information device 5a,
Modulation processing is performed on the transmission data by the modulator 1-1 using a plurality of frequency components as carrier waves. The modulation processing includes, for example, orthogonal frequency division multiplexing (OFDM) and multicarrier phase modulation. Modulation section 1-1
Is converted into an analog signal by a digital / analog converter (D / A converter) 1-3, and the output signal of the D / A converter 1-3 is amplified by an amplifier 1-4 to be combined with a transmission signal. Output to the circuit 2. Here, the D / A converter 1-3 and the amplifier 1-4 are grounded so that the signal level reference is the same as the terminal 2-1-3 of the transformer 2-1.
The amplifier 1-4 applies a gain to the signal output from the D / A converter 1-3 regardless of the frequency component.

A test data generator 1-2 for generating a specific transmission data pattern (test data) receives
Test data is output to the modulation section 1-1 and the comparison correction section 1-5. The modulation section 1-1 modulates the transmission data and the test data, but modulates the test data when there is no transmission data. When receiving a signal transmitted by another communication device, the received signal input from the coupling circuit 2 is converted into an analog-digital converter (A
/ D converter) 1-6, and converts the digital signal into a digital signal. The signal level reference of the A / D converter 1-6 is grounded so as to be the same as the terminal 2-1-3 of the transformer 2-1.

The demodulation section 1-7 outputs the received data to the comparison / correction section 1-5 and the information equipment 5a. Comparison correction section 1-5
Then, when test data is input, the levels of the received data and the test data are compared for each frequency component, and correction data for correcting the level of each frequency component is output to the modulation section 1-1 based on the result. The modulator 1-1 modulates and outputs a signal level for each frequency component recognized from the correction data when performing modulation processing on transmission data.

The test data and the correction data will be described with reference to FIG. 2 which is a specific example. FIG. 2A shows test data in which a constant signal level A0 is set at frequencies f1 to f8 in the communication frequency band. The test data is supplied to the modulation unit 1-1, the D / A converter 1-3, and the amplifier 1-4.
And is output to the coupling circuit 2 as a transmission signal. As described above, the transmission signal is transmitted from coil L3 of transformer 2-1 to L3.
1 and is affected by the power line impedance in the coil L1, and is input as a monitor signal from the coil L2 by the signal processing circuit 1.

When the power line impedance is at frequencies f3 and f
4 and f5, the monitor signal corresponding to the test data is demodulated by the demodulator 1-7.
When demodulation is performed, the relationship of the signal level with respect to the frequencies f1 to f8 is as shown in FIG. However, in this example, in order to make the description easy to understand, the turns ratio of each of the coils L1, L2, and L3 is set to 1, and the gain of the amplifier 1-4 is set to 1.
If the turns ratio is different, the signal level is proportional to the turns ratio. If the gain of the amplifier 1-4 is not 1, the signal level may be multiplied by the gain. In the comparison and correction unit 1-5, the relationship between each frequency of the test data and the signal level (FIG. 2)
(A)) is compared with the relation between each frequency of the monitor signal and the signal level (FIG. 2B), and the increase / decrease of the signal level is calculated for each frequency.

2 (a) and 2 (b), it can be seen that the level C0 at the frequency f3, the level C1 at the frequency f4, the level C2 at the frequency f5, and no increase or decrease at other frequencies. In other words, in the modulation section 1-1, the level C0 at the frequency f3, the level C1 at the frequency f4, and the frequency f
5 and the level C2 is added, the relationship of FIG.
(A). From this, the comparison correction section 1-5
Then, the correction data that makes the signal levels of the test data and the monitor signal equal at each frequency, specifically, the information of FIG. 2C is output to the modulation unit 1-1. Modulation unit 1-
In 1, the signal level is determined for each frequency from the correction data, and the signal level is adjusted for each frequency in the subsequent modulation processing.

The test data shown in FIG. 2A has a constant signal level A0 at each frequency. However, if the signal level is not constant but is a known signal level, the signal level at each frequency of the monitor signal is determined. Is obtained, and the difference may be used as correction data. In the embodiment of FIG. 1, the received signal is directly input to the A / D converter 1-6, but a receiving amplifier is provided in consideration of the fact that the signal level of the received signal is attenuated over the entire communication frequency band. In this case, the reception data output from the demodulation unit 1-7 is multiplied by the gain of the reception amplifier. For this reason, in the comparison by the comparison correction unit 1-5, the received data is attenuated by the gain of the receiving amplifier.
Alternatively, the test data output from the test data generator 1-2 may be corrected by multiplying the test data by the gain of the receiving amplifier.

As described above, according to the present invention, a known signal level is transmitted as test data for each frequency within the communication frequency band, and the signal level changes for each frequency due to the influence of the power line impedance. Receives monitor signals and corrects the signal level for each frequency based on the change in signal level between the monitor signal and test data. Signal level and stable communication can be realized.

FIG. 3 shows a second embodiment of the present invention. This measures the noise superimposed on the power line 4 and
This is an example of a communication device that corrects a signal level of transmission data to be equal to or higher than a noise level. The difference from the communication device of FIG. 1 is that the test data generation unit and the comparison correction unit are excluded,
The reception status indicating the presence / absence of reception data is indicated by a demodulation unit 1-7.
From the A / D converter 1-6 in response to a noise measurement command from the modulation unit 1-1, and to the noise level determination unit 1-8, based on the determination result. The modified data is output to the modulation unit 1-1, and the other configurations and functions are the same as those in FIG. Hereinafter, a specific description will be given.

The modulation section 1-1 outputs a noise measurement command at an arbitrary timing when there is no transmission data and no reception data. In the modulation section 1-1, it is easy to determine that there is no transmission data in the modulation section 1-1 that directly inputs the transmission data, and it is recognized from the reception status that there is no reception data. The noise level determination unit 1-8 measures the level of the received signal converted into a digital signal by the A / D converter 1-6 by inputting a noise measurement command.

As described above, the noise measurement command is output from the modulation section 1-1 when there is no transmission data and no reception data. Therefore, the transmission line itself and the reception data from other communication devices exist on the power line 4. I haven't. Therefore, only the noise superimposed on the power line exists in the reception signal measured by the noise level determination unit 1-8, and the noise level in the communication frequency band can be measured.

In general, it is well known that in order to realize communication, the ratio between the signal level and the noise level (called S / N) must be equal to or greater than a threshold. Therefore, when the noise level is high, the level of the signal transmitted and received must be increased accordingly. The noise level determination unit 1-8 calculates the S / N for each frequency component using the measured noise level and the signal level of the modulation unit 1-1 stored in advance.

FIG. 4A shows an example. As shown, S0 is a threshold value. From FIG. 4 (a), with respect to the threshold value S0, z3 dB is obtained at the frequencies f1 and f5.
Z2 dB at frequency f2, z at frequencies f3 and f4
It can be seen that the frequency is low by 1 dB, z4 dB at frequencies f6 and f7, and z5 dB at frequency f8. Therefore, correction data for increasing the signal level is calculated such that the S / N is equal to or greater than the threshold value S0, and the modulation unit 1-
Output to 1. FIG. 4B shows correction data for FIG. The modulation unit 1-1 sets the signal level based on the correction data to z3 dB at the frequencies f1 and f5, z2 dB at the frequency f2, z1 dB at the frequencies f3 and f4, and z4 dB at the frequencies f6 and f7.
At the frequency f8, the frequency is increased by z5 dB.

The correction data is a frequency component having the lowest S / N. In FIG. 4A, the threshold value S0 is obtained even if z5 dB is uniformly increased at each frequency with reference to the frequency f8.
However, at the frequencies f3 and f4, the signal level may become too large and exceed the input range of the D / A converter 1-3. In this case, although not shown, a process for changing the input range of the modulator 1-1 to the D / A converter 1-3 may be added.

As described above, according to the present invention, when the transmission signal and the reception signal of the communication device are not propagated on the power line, the noise superimposed on the power line is measured, and the communication frequency band is determined using the measurement result. S / N for each frequency component in
Since the signal level is increased so that is equal to or more than the threshold value, stable communication can be realized even if noise that changes over time occurs.

Also, the embodiment of FIG. 1 and the embodiment of FIG. 3 are combined to adjust the signal level using the correction data obtained from the test data and to adjust the signal level to make the S / N equal to or higher than the threshold level. It goes without saying that the correction can be realized by the same signal processing circuit. In this case, the influence of the power line impedance fluctuation and the noise can be corrected simultaneously.

FIG. 5 shows a third embodiment of the present invention. The difference from the communication device of FIG.
Is input to the test data detector 1a-9, and when it is detected that the received data is test data, the detection signal is input from the test data generator 1a-2 by the comparison corrector 1a-5. The test data thus received is compared with the received data, and correction data for adjusting the signal level for each frequency is output to the modulator 1a-1. Other configurations and functions are the same as those in FIG.

In the embodiment shown in FIG. 5, the test data output from the test data generator 1a-2 is supplied to the modulator 1a-1, the D / A converter 1a-3, and the amplifier 1 as in the case of FIG.
The signal is transmitted as a transmission signal via a-4. As described above, this transmission signal is used as a monitor signal by its own demodulation unit 1a-
7, but can also be received as a received signal by the other communication device 10b. Here, the communication device 10b is the communication device 1
Since it has exactly the same configuration and function as Oa, detailed description is omitted. The received signal received by the signal processing circuit 1b of the communication device 10b is converted into an A / D converter 1b-6 and a demodulator 1b.
The data is output as received data via b-7. If the received signal is test data transmitted by another communication device 10a, the test data is detected by the test data detection unit 1b-9. As a specific detection method, a technique is known in which a communication device that transmits test data adds specific pattern data (header) indicating the test data to the head of the test data, and another communication device monitors the presence or absence of the header. Have been.

Also in this embodiment, header detection can be used for test data detection by the test data detection section 1b-9. In the comparison correction unit 1b-5,
When the detection signal from the test data detection section 1b-9 is input, the test data output from the test data generation section 1b-2 is compared with the received data. Test data generator 1b-
2 includes a test data generator 1a of another communication device 10a.
Since the same test data as that of FIG. 2 is generated, the comparison and correction unit 1b-5 performs the comparison and correction unit 1-5 of FIG.
In the same manner as described above, the correction data can be output to the modulation unit 1b-1. Hereinafter, the adjustment of the signal level by the modulator 1b-1 is the same as that in FIG. Further, by inputting the correction data output from the comparison / correction unit 1b-5 to the demodulation unit 1b-7, an application in which the signal level is adjusted for each frequency component during demodulation can be easily considered.

As described above, according to the present invention, known test data is transmitted from the communication device on the transmission side, and a reception signal affected by the power line impedance is received by the communication device on the reception side. Since the receiving communication device compares the received signal with the test data common to the transmitting communication device and corrects the signal level, it is necessary for transmission and reception even if an unspecified number of electrical devices are connected to the power line and the power line impedance fluctuates. Signal level and stable communication can be realized.

[0038]

According to the present invention, it is possible to realize a power line communication device capable of performing stable communication even when a large impedance fluctuation occurs in a power line or when noise that changes with time occurs.

[Brief description of the drawings]

FIG. 1 is a block diagram of a communication apparatus according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing an example of test data and correction data in the first embodiment.

FIG. 3 is a block diagram of a communication apparatus according to a second embodiment of the present invention.

FIG. 4 is a characteristic diagram showing an example of a signal level / noise level ratio and correction data in the second embodiment.

FIG. 5 is a block diagram of a communication apparatus according to a third embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Signal processing circuit, 2 ... Coupling circuit, 1-1 ... Modulation, 1-
2 ... test data generator, 1-5 ... comparator / corrector, 1-7
... Demodulator, 1-8. Noise level determiner, 1a-5, 1
b-5: Test data detection unit, 4: Power line, 10a, 1
0b: Communication device.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Setsuo Arita 7-2-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Power & Electric Development Laboratory, Hitachi, Ltd. (72) Inventor Izumi Yamada Omika-cho, Hitachi City, Ibaraki Prefecture 7-2-1, Hitachi, Ltd. Electricity and Electricity Development Laboratory Co., Ltd. (72) Inventor Takuya Sugawara 7-2-1, Omika-cho, Hitachi City, Ibaraki Prefecture F-term in Hitachi, Ltd. Electric Power and Electricity Development Laboratory Reference) 5K038 AA07 CC09 DD21 EE02 EE08 5K046 AA03 BA05 BB05 CC02 CC05 CC09 CC17 DD01 DD14 DD25 PS03 PS33 PS52

Claims (4)

[Claims] A modulation section for outputting a transmission signal composed of a plurality of frequency components to a power line; and a demodulation section for inputting a reception signal from the power line, wherein a test signal output from the modulation section is monitored by a monitor signal. As input to the demodulation unit,
A signal level is compared for each frequency component of the monitor signal and the test signal, and a transmission signal whose signal level is corrected such that the signal level of the monitor signal is equal to or higher than the signal level of the test signal for each frequency component is output. A power line communication device characterized by comprising means. And a demodulation section for outputting a transmission signal comprising a plurality of frequency components to the power line, and a demodulation section for inputting a reception signal from the power line, wherein a noise level of a communication frequency band superimposed on the power line is reduced. Measure for each frequency component,
A power line communication device, comprising: means for outputting, from the modulation unit, a transmission signal in which a ratio between the noise level and the level of the transmission signal is equal to or greater than a predetermined threshold value for each frequency component. 3. A test signal output from the modulation unit of the power line communication device, comprising: a modulation unit that outputs a transmission signal including a plurality of frequency components to a power line; and a demodulation unit that inputs a reception signal from the power line. And the signal level is compared for each frequency component of the monitor signal and the test signal, and the signal level of the monitor signal is higher than the signal level of the test signal for each frequency component. A power line communication method, comprising: outputting a transmission signal in which the transmission signal is corrected. 4. A power line communication apparatus comprising: a modulation unit that outputs a transmission signal including a plurality of frequency components to a power line; and a demodulation unit that inputs a reception signal from the power line. A noise level is measured for each frequency component, and a transmission signal whose ratio between the noise level and the level of the transmission signal is equal to or greater than a predetermined threshold value for each frequency component is output from the modulation unit. Power line communication method.