JP3423601B2 - Distribution line transport method by quadrature amplitude modulation - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses an AC power distribution line as a signal transmission line, superimposes a modulated carrier wave on a commercial frequency to transmit data, and performs various kinds of monitoring and control in a distribution system. The present invention relates to an improvement of a distribution line carrying method for carrying out.

[0002]

2. Description of the Related Art In a conventional distribution line carrier method for transmitting data by superimposing a carrier wave on a commercial frequency of an AC power distribution line, a synchronization method using a commercial frequency phase as a unit between transmission and reception is used. 100 baud at 50 Hz
By performing a significant number 2 of amplitude or frequency in the modulation section of d), a data transmission rate of 100 bit / s is realized, and automatic meter reading for reading each home electric energy value is performed remotely.

[0003]

A data transmission rate of 100 bits is expected in view of diversification of transmission information such as power demand management other than automatic meter reading expected in the future and expandability of other media information.
It is difficult to use the distribution line transportation method of / s.

However, in communication using a distribution line to which various devices are connected as a medium, general transmission quality cannot be ensured, and in order to improve the data transmission speed, it is peculiar to withstand the characteristics of the distribution line. Different transmission methods and modulation / demodulation processing are required. That is, in order to increase the number of channels by using all the phase ranges in one cycle of the commercial frequency in order to increase the data transmission rate, even if signals with a constant amplitude are superimposed, the phase is 0, π. The amplitude is large near
The amplitude becomes small in the vicinity of / 2,3π / 2, and it seems as if the amplitude was modulated. Therefore, it is unavoidable to use the low noise region near the phase of 0, π. If the width of one channel is narrowed and the number of channels is increased by using the low noise region near the phases 0 and π, the degree of code interference increases in the front and rear channels due to the influence of line distortion. The width of one channel cannot be made too small. Further, if the number of phases of phase modulation is increased by using quadrature phase modulation, the data transmission speed increases, but it is difficult to determine the phase difference on the receiving side. Therefore,
In the conventional way of thinking, it is difficult to improve the data transmission rate. (Object of the Invention) A first object of the present invention is to provide a phase and level generated between channels due to the non-linearity of impedance of a load device connected to a distribution line in order to enable improvement of data transmission rate. It is an object of the present invention to provide a method for conveying a distribution line by quadrature amplitude modulation, which can eliminate the influence of the fluctuation of

A second object of the present invention is to use a quadrature amplitude modulation method capable of eliminating a carrier phase synchronization deviation due to the influence of load fluctuations with the passage of time in order to improve the data transmission rate. It is to provide an electric wire transportation method.

[0006]

In order to achieve the first object, the present invention according to claim 1 superimposes a carrier wave quadrature amplitude modulated by data on a commercial frequency of a distribution line. A distribution line carrier method using quadrature amplitude modulation for data transmission, in which a carrier wave superimposing section centered on at least one of phase 0 and phase π of a commercial frequency is divided into three or more channels, and on the transmission side, Prior to superimposing the carrier quadrature-amplitude modulated by the data, an unmodulated carrier is superposed as a reference signal on all channels of the carrier superimposing section of the first cycle of the commercial frequency,
An unmodulated carrier and a carrier obtained by reversing the polarity of the carrier are alternately superposed as a synchronization signal on a channel in the carrier-superimposing section of the second cycle of the commercial frequency, and the reference signal and the synchronization signal are multiplied on the receiving side. From the detected waveform, the center point of each channel is detected and stored, and the determination level for each channel is set based on the multiplied and detected waveform. When demodulating the carrier quadrature amplitude modulated by the data, The amplitude of the carrier wave at the center point of each channel is judged by the judgment level.

In order to achieve the above second object,
The present invention according to claim 2 is such that the third side of commercial frequency is used on the transmitting side.
Superimposing an unmodulated carrier as a pilot signal on the first channel of each carrier superimposing section after the cycle,
A carrier that is quadrature-amplitude-modulated by data is superimposed on a channel other than the first channel, and on the receiving side, based on the detected in-phase component and the detected quadrature component of the pilot signal, the carrier wave superimposed on the channel other than the first channel is detected. It is characterized in that the phase correction of the detection output is performed for each of the carrier wave superimposing sections.

[0008]

FIG. 1 is a diagram showing a channel arrangement on a commercial frequency according to an embodiment of the present invention.
A low noise region centered on phases 0 and π of the commercial frequency 1 of 50 Hz or 60 Hz is used as the carrier wave superimposing section 2, and the carrier wave superimposing section 2 is used for four channels CH1,
Divide into CH2, CH3 and CH4. Then, on the transmitting side, in the first channel CH1 of each carrier wave superimposing section 2,
Unmodulated (reference phase) carrier wave (for example, carrier frequency is 7.
5 kHz ), a pilot signal P is superimposed, and channels CH2 to CH4 other than the first channel CH1 are
Carrier wave D1 quadrature amplitude modulated (QAM) by data
Superimpose D9, .... 16 values as data, that is, 4
Bit, as shown in the phase layout diagram of FIG.
The amplitude and polarity of the carrier wave are determined so as to take in-phase 4-value and quadrature 4-value. For example, if the maximum amplitude is 1, the four values are determined to have amplitudes of ± 1 and ± 1/3. Therefore, one channel can transmit 4 bits, and since there are two carrier wave superimposing sections 2 in one cycle of the commercial frequency 1, at the commercial frequency 50 Hz, 4 bits × 3 channels × 2 carrier wave superimposing sections × 50 Hz = 1200 bit. It can be a data transmission rate of / s. Commercial frequency 1
Only the carrier wave superimposing section 2 whose phase is centered on π (or 0) may be used. In that case, the data transmission rate is 600 bit / s. Further, the number of channels is not limited to four and may be three or more.

Before transmitting data using the quadrature amplitude modulation method (QAM), it is necessary to transmit a reference signal and a synchronization signal in order to synchronize transmission and reception. As shown in FIG. 3, on the transmission side, first, carrier wave superimposing sections 2a, 2 centered on the phases π and 0 of the first cycle of the commercial frequency 1 are set.
The unmodulated carrier I ₀ is superimposed on all the channels CH1 to CH4 of b as the reference signal, and then unmodulated on the channels CH1 and CH3 of the carrier superimposing sections 2c and 2d of the second cycle of the commercial frequency 1. The carrier I ₀ is alternately superposed on the channels CH2 and CH4 as the synchronizing signal, and the carrier I ₁ obtained by reversing the polarity of the carrier I ₀ as shown in FIG. 4 is used as the synchronization signal. Multiply detection (synchronous detection) is performed with the synchronization signal of the carrier wave superimposing section 2c, and the reference signal of the carrier wave superimposing section 2b and the synchronization signal of the carrier wave superimposing section 2d are multiply detected. The multiplication detection waveform 3 becomes as shown in FIG. 5, and the 0 cross point is detected as the channel switching point, and the point of the time T between the 0 cross points is 1/2 as the center point of the channel. , Memorize each. Also, as shown in FIG.
± 2 / of the maximum amplitude I ₀ of each channel of the multiplication detection waveform 3
3 is set and stored as the determination levels ± L1 to ± L4 for each channel.

Thus, the center point of each channel is detected and stored, and the determination level for each channel is set on the basis of the waveform subjected to the multiplicative detection, whereby the non-linearity of the impedance of the load equipment connected to the distribution line is set. Channels CH1 to C due to (static characteristics of distribution line)
It is possible to eliminate the influence of phase and level fluctuations that occur for each H4.

The carrier wave superimposing sections 2a and 2c centering on the phase π and the carrier wave superimposing section 2b and centering on the phase 0 are provided.
Since the line characteristic is different from that of 2d, it is desirable to separately detect and store the center point of the channel by transmitting and receiving the reference signal and the synchronizing signal, and set and store the determination level, as shown in FIG.

After the transmission of the reference signal and the synchronization signal,
As already described with reference to FIG. 1, in the first channel CH1 of each carrier wave superimposing section 2, an unmodulated carrier wave (carrier wave I
₀ equivalent) superimposes the pilot signal P consisting of, in the header channel CH1 other channels CH2～CH4, quadrature amplitude modulated carrier D by the data of 16 values
1-D9, ... are superimposed. At this time, for example, when an unmodulated pilot signal P is received, a phase shift θ occurs on the receiving side as shown in FIG. 7. Also, carrier wave D1
The same phase shift occurs when receiving ~ D9, .... Therefore, it is necessary for the receiving side to correct this phase shift.

In one embodiment of the present invention, on the receiving side, based on the detected in-phase component and the detected quadrature component of the unmodulated pilot signal P, the carrier waves D1 to CH4 other than the first channel CH1 are superimposed on the channels CH2 to CH4. D9,
The phase correction of the detection output of ... is performed for each carrier wave superimposing section 2. That is, the detected in-phase components of the carrier waves D1 to D3 quadrature amplitude-modulated by the pilot signal P and data are P _I , a ₁ , a ₂ , and a ₃ , respectively, and the carrier wave D1 also quadrature amplitude-modulated by the pilot signal P and data. The detected quadrature components of D3 to P3 are respectively P _Q , b ₁ ,
Assuming b ₂ and b ₃ , they are as shown in FIG. 8, for example. In this case, the phase correction is performed by calculating the following equation.

I _x = a _x P _I + b _x P _Q Q _X = b _X P _I −a _X P _Q where x = 1, 2, 3,
By the calculation of the above equation, the phase-corrected in-phase component amplitude I _x and quadrature component amplitude Q _x of the carriers D1 to D9, ... In each channel other than the first channel CH1 are obtained.

By performing the phase correction for each carrier wave superimposing section 2 in this way, it is possible to eliminate the carrier wave phase synchronization shift due to the influence of the load fluctuation with the passage of time.

Carrier waves D1 to D at the center point of each channel
The phase-corrected in-phase component amplitude I _x and quadrature component amplitude Q _x of 9, ...
It is determined whether it is larger or smaller than 2 to ± L4, and as a result, as shown in FIG. 9, 4-bit 16-value data (d ₁ , d ₂ ,
d ₃ , d ₄ ) are demodulated.

FIG. 10 shows an example of a transmitting side apparatus that executes the method of the present invention.

The synchronization control circuit 4 has a commercial frequency synchronization circuit 5 in order to synchronize transmission and reception before transmitting data.
Only the four-level amplitude modulation circuit 6 is operated while being synchronized with the commercial frequency by the output of. That is, the four-valued amplitude modulation circuit 6
Generates an unmodulated carrier I ₀ as a reference signal in all the channels CH1 to CH4 of the carrier wave superimposing sections 2a and 2b centered on the phase π and 0 of the first cycle of the commercial frequency 1 and adds it to the adder. It is superposed on the distribution line by the distribution line injection circuit 8 via 7. Next, the channels CH1 and C of the carrier wave superimposing sections 2c and 2d of the second cycle of the commercial frequency 1
Carrier wave I _0, which is not modulated by H3, is transmitted to channels CH2 and C.
The carrier I ₁ where the carrier I ₀ to the polarity reversal at H4, generated respectively alternately as a synchronization signal, is superimposed on the distribution line by similarly distribution line injection circuit 8.

After that, the four-valued amplitude modulation circuit 6 carries out the amplitude modulation of the unmodulated pilot signal P and the in-phase component data d ₁ and d ₂ sent from the code generation circuit 9 on the carrier wave of the carrier wave generation circuit 10. Is output. On the other hand, the four-valued amplitude modulation circuit 11 amplitude-modulates the quadrature division data d ₃ and d ₄ sent from the code generation circuit 9, and the carrier of the carrier generation circuit 10 is π / 2 by the π / 2 phase shift circuit 12. The phase-shifted carrier wave is output. The adder 7 adds these carriers into a quadrature amplitude modulated carrier, and the distribution line injection circuit 8
A pilot signal P consisting of an unmodulated carrier wave is superimposed on the head channel CH1 of each carrier wave superimposing section 2, and carrier waves D1 to D9, ..., Which are quadrature amplitude modulated by data, are superimposed on the channels CH2 to CH4 other than the head channel CH1. Superimpose.

FIG. 11 shows an example of the receiving side apparatus for executing the method of the present invention.

The bandpass filter 13 separates the carrier wave from the commercial frequency 1 of the distribution line. As described above, the synchronization control circuit 14 performs the multiplicative detection (synchronous detection) of the reference signal of the carrier wave superimposing section 2a and the synchronizing signal of the carrier wave superimposing section 2c while synchronizing with the commercial frequency 1, and the reference signal of the carrier wave superimposing section 2b. The signal and the synchronization signal in the carrier wave superimposing section 2d are multiplied and detected.
Then, the 0 cross point of the multiplication detection waveform 3 (FIG. 5) is detected as the channel switching point, and the point of half the time T between the 0 cross points is set as the center point of the channel. And the determination levels ± L1 to ± L4 for each channel are set and stored in the memory 15.

The in-phase signal generation circuit 16 generates the in-phase signal of the carrier wave in synchronization with the commercial frequency 1 of the distribution line, and the quadrature signal generation circuit 17 synchronizes with the commercial frequency 1 of the distribution line and is the in-phase signal. A quadrature signal of carrier waves having a phase difference of π / 2 is generated.
The multiplier 18 quadrature-amplitude-modulates the carrier waves D1 to D9 with the unmodulated pilot signal P and 16-valued data.
Is multiplied by an in-phase signal to perform multiplication detection, and the multiplier 19 multiplies the carriers D1 to D9, ..., Which are quadrature amplitude modulated by the unmodulated pilot signal P and 16-valued data, by the quadrature signal and performs multiplication detection. I do. The phase correction circuits 20 and 21 perform phase correction of the multiplication detection outputs output from the low pass filters 22 and 23. That is, the detected in-phase component P _I and the detected quadrature component P _Q of the pilot signal P are obtained, and the phase correction of the detected output of the carrier waves D1 to D9, ... Is performed for each carrier wave superimposing section 2 based on these.

The decision circuits 24 and 25 store the phase-corrected in-phase component amplitude I _x and quadrature component amplitude Q _x of the carriers D1 to D9, ... At the center point of each channel in the memory 15 channel. It is determined whether each level is larger or smaller than the determination level ± L2 to ± L4, and 16-value data (d ₁ ,
d ₂ , d ₃ , d ₄ ) are output.

[0024]

As described above, according to the present invention of claim 1, the carrier wave superimposing section centered on at least one of the phase 0 and the phase π of the commercial frequency is divided into three or more channels. However, on the transmitting side, prior to the superimposition of the carrier quadrature amplitude modulated by the data, the first of the commercial frequency is transmitted.
Carrier is superimposed on all channels of the carrier wave superimposing section of the cycle as a reference signal, and the carrier of the unmodulated carrier wave and the polarity of the carrier wave is inverted on the channel of the carrier wave superimposing section of the second cycle of the commercial frequency. Are alternately superposed as synchronization signals, and on the receiving side, from the waveform obtained by multiplying and detecting the reference signal and the synchronizing signal, the center point of each channel is detected and stored, and based on the waveforms obtained by multiplying and detecting, A decision level is set for each channel, and when demodulating a carrier quadrature-amplitude-modulated by data, the amplitude of the carrier at the center point of each channel is decided by the decision level. Eliminating the effects of phase and level fluctuations between channels due to the impedance non-linearity of the load equipment It can be.

Further, according to the present invention as set forth in claim 2, on the transmitting side, an unmodulated carrier is superposed as a pilot signal on the head channel of each carrier superposing section after the third cycle of the commercial frequency, A carrier, which is quadrature-amplitude modulated by data, is superimposed on a channel other than the first channel, and on the receiving side, based on the detected in-phase component and detected quadrature component of the pilot signal, the carrier wave detected on the channel other than the first channel is detected. Since the phase correction of the output is performed for each of the carrier wave superimposing sections, it is possible to eliminate the carrier phase synchronism shift due to the influence of the load fluctuation with the passage of time.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of channel arrangement on a commercial frequency according to an embodiment of the present invention.

FIG. 2 is a diagram showing a 16-value phase arrangement when quadrature amplitude modulation is used.

FIG. 3 is a diagram showing a reference signal and a synchronization signal in the embodiment of the present invention.

FIG. 4 is a diagram showing a phase relationship between carrier I ₀ and carrier I ₁ in FIG.

FIG. 5 is a diagram showing switching points and center points of channels on the commercial frequency on the receiving side.

FIG. 6 is a diagram showing the determination level of each channel on the commercial frequency on the receiving side.

FIG. 7 is a diagram showing a phase shift of pilot signals on the receiving side.

FIG. 8 is a diagram showing a detected in-phase component and a detected quadrature component before phase correction.

FIG. 9 is a diagram showing a relationship between 16 values and determination levels.

FIG. 10 is a block diagram showing an example of a transmitting side apparatus that executes the method of the present invention.

FIG. 11 is a block diagram showing an example of a receiving side apparatus that executes the method of the present invention.

[Explanation of symbols]

1 commercial frequency 2,2a, 2b, 2c, 2d carrier superimposed section 3 multiplies detection waveform CH1~CH4 channel P pilot signal D1~D9 carrier d ₁ which is quadrature amplitude modulated by the _{data, d 2, d 3, d} 4 16 value 4-bit data I ₀ Carrier wave with no modulation (reference phase) I ₁ Carrier wave with opposite polarity to carrier 1 ₀ without modulation L1 to L4 Judgment level θ Phase shift P _I Detection in-phase component of pilot signal P P _Q pilot signal P detection quadrature component of the quadrature amplitude modulated carrier by detecting the in-phase component b ₁ ~b ₃ data quadrature amplitude modulated carrier by detecting the quadrature component a ₁ ~a ₃ data

Claims (2)

(57) [Claims] 1. A distribution line carrier method by quadrature amplitude modulation for transmitting data by superimposing a carrier quadrature amplitude modulated by data on a commercial frequency of a distribution line, wherein a phase 0 and a phase π of a commercial frequency are used. Of the carrier wave in the first cycle of the commercial frequency, prior to superimposing the carrier wave quadrature amplitude modulated by the data, on the transmitting side. An unmodulated carrier is superposed as a reference signal on all channels in the superimposing section, and an unmodulated carrier and a carrier obtained by reversing the polarity of the carrier are used as synchronization signals on the channels in the carrier superimposing section in the second cycle of the commercial frequency. Alternately superposed, and the receiving side detects and stores the center point of each channel from the waveform obtained by multiplying and detecting the reference signal and the synchronization signal. In both cases, the determination level for each channel is set based on the waveform detected by the multiplication, and when demodulating the carrier quadrature amplitude modulated by the data, the amplitude of the carrier at the center point of each channel is determined by the determination level. A method of transporting a distribution line by quadrature amplitude modulation, which is characterized in that 2. The transmitting side superimposes a non-modulated carrier wave as a pilot signal on the head channel of each carrier wave superimposing section after the third cycle of the commercial frequency, and quadrature amplitude modulates the data on channels other than the head channel by data. The received carrier is superposed, and on the receiving side, based on the detected in-phase component and the detected quadrature component of the pilot signal, the phase correction of the detected output of the carrier superposed on the channel other than the first channel is performed for each of the carrier superimposed sections. The method for conveying a distribution line by quadrature amplitude modulation according to claim 1, wherein