JPH07101855B2 - Distribution line carrier signal phase modulation / demodulation method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a distribution line carrier signal phase modulation / demodulation method for phase-modulating and demodulating a low-frequency carrier signal carried on a distribution line as a signal transmission path. .

(Background of the Invention) There are a ripple control system and a current signal transmission system as a distribution line transmission system that uses a distribution line as a transmission line of a transmission signal. The former is a voltage signal on a bus of a distribution substation that is a power source end. Is transmitted and information is transmitted, and the latter is a method in which information is transmitted from the load side of the distribution system to the substation side as a current signal.

100-600Hz with good signal transmission characteristics on distribution lines
The frequency of the carrier signal is a relatively low frequency.

The distribution line carrier system is widely used because of its stable signal transfer rate, but the distribution line has a very large level of commercial voltage harmonic voltage and current in the above-mentioned relatively low frequency band. However, since it becomes noise to the signal, a narrow band that avoids this harmonic noise is set as the signal transmission band, so that the transmission speed of the carrier signal is limited to about 10 to 20 bps.

On the other hand, in recent years, the functions of distribution automation systems to which the distribution line carrier system is applied have become more sophisticated, and the amount of information to be transmitted has increased accordingly. There is a demand for increased speed.

Although binary modulation is generally used in distribution line transportation,
As a method of speeding up signal transmission within the limited band as described above, multi-level modulation widely used in general communication line carriers such as data communication systems, that is, the number of significant states of modulation is set to a normal binary value. There is also a method for multi-valued modulation. If this multi-valued modulation can be adopted, the signal transmission speed can be improved in the same band as the conventional one.

Conventionally, in the distribution line transportation, the amplitude modulation system and the frequency shift modulation system have been adopted as the modulation system because it is easy to realize the device at low cost. When it is adopted for transportation, there are the following problems.

When the signal level is the same as the conventional one, the level difference between the levels of the modulation by the multi-level code is smaller than that of the binary code, so that the reliability against noise is lowered.

The power distribution line has a large noise level and fluctuation as compared with a general communication line, and the reliability of modulation / demodulation by multilevel codes may be significantly reduced.

Therefore, the most suitable modulation method for performing the above-mentioned multi-valued conversion is the phase modulation method because the degree of error rate increase due to the multi-valued conversion is smaller than that of the amplitude modulation / frequency shift keying modulation. However, there are the following problems.

As the demodulation method of phase modulation, a method of generating a phase reference signal from the received signal and demodulating the received signal by it,
Generally, two methods (differential detection) of demodulating a received signal using a signal delayed by a unit modulation section as a phase reference signal are generally used.

The demodulation method of (1) requires stable generation of a phase reference signal from the received signal, and the demodulation method of (1) requires a signal delay unit for a unit modulation section, which complicates the circuit configuration. Inevitably, the rise in equipment prices.

As described above, the phase modulation method has a complicated modulation / demodulation circuit configuration, and the apparatus is expensive. Therefore, the phase modulation method has not been conventionally used as a modulation method in distribution line transportation.

(Object of the Invention) An object of the present invention is to solve the above-mentioned problems, to make the circuit configuration of phase modulation / demodulation simple and inexpensive, and to realize stable signal transmission. It is to provide a phase modulation / demodulation method.

(Characteristics of the Invention) In order to achieve the above object, the present invention sets a carrier signal frequency to a frequency obtained by a harmonic of a commercial frequency of a distribution line or a frequency division of the harmonic, and transmits and receives the carrier signal. On both sides, a phase reference signal of the carrier signal frequency is generated from the commercial frequency, and on the transmission side, phase modulation is performed by changing the phase of the phase reference signal according to information,
On the receiving side, the carrier signal received using the phase reference signal is demodulated so that the phase reference signal can be obtained by a simple filter, and the phase shift between the sending side and the receiving side is deviated. Is characterized in that

(Embodiment of the Invention) FIG. 1 is a block diagram of a phase modulation / demodulation type transmission side circuit embodying the present invention.

First, the transmission data is filtered by the transmission filter 1 which is a roll-off filter that limits the spectrum of the transmission data, and is transmitted to the modulation circuit 2.

The pulsing circuit 3 generates harmonics from the commercial frequency, and the harmonic generation filter 4 generates harmonics of a desired frequency. (When the harmonics are of even order, the pulse duty of the pulse conversion circuit 3 needs to be set to a pulse duty other than 1: 1.) This harmonic is pulsed again by the pulse conversion circuit 5, and the frequency division circuit 6 A pulse having a predetermined carrier signal frequency is obtained at.

The carrier signal frequency pulse thus generated is made into a sine wave by the phase reference signal filter 7, and this becomes a phase reference signal used for phase modulation.

Also in this method, since the carrier signal frequency is usually between the harmonics of the commercial frequency, the pulsing circuit 5, the frequency dividing circuit 6 and the phase reference signal filter 7 are required, but the commercial frequency of the low noise level is used. These are not necessary when the even harmonics are used as the carrier signal frequency.

The modulation circuit 2 is a delay circuit and delays the phase reference signal generated as described above according to the transmission data signal output from the transmission filter 1 to perform phase modulation. The phase-modulated carrier signal has its unnecessary spectrum removed by the bandpass filter 8, is amplified to a predetermined signal level by the transmission amplifier 9, and is injected into the distribution line through the coupling circuit 10.

FIG. 2 is a block diagram of a phase modulation / demodulation type receiving side circuit embodying the present invention.

The carrier signal detected from the distribution line is filtered by the bandpass filter 11, and the carrier detection circuit 12 detects the arrival of the carrier signal.

Pulse conversion circuit 13, harmonic generation filter 14, pulse conversion circuit
15, the frequency dividing circuit 16 and the phase reference signal filter 17 are exactly the same circuits as the transmitting side circuit of FIG. 1, and generate a phase reference signal for demodulation from the commercial frequency.

The phase control circuit (delay circuit) 18 receives the control signal from the demodulation control circuit 19 activated by the signal from the carrier detection circuit 12 so that the phase of the received signal and the phase of the phase reference signal are a predetermined phase at the beginning of the received signal. The phase reference signal is delayed so that it has a relationship, and thereafter the phase relationship is maintained during the reception of the signal.

The phase reference signal from the phase control circuit 18 and the received data signal from the bandpass filter 11 are subjected to multiplication detection by the multiplication circuit 20, waveform shaped by the reception filter 21, and demodulated and output as reception data by the demodulation control circuit 19. .

As described above, the method of the present invention is performed on the transmitting side and the receiving side.
This is a method of using a phase reference signal generated from an originally common commercial frequency, and once phase synchronization is performed on the receiving side, thereafter, stable demodulation based on a phase reference can be performed.

The phase modulation / demodulation circuit configuration can also be obtained by a simple filter, and therefore, the phase modulation can be adopted at a low cost in the distribution line carrier system.

Next, in the above-described phase modulation / demodulation method, when performing polyphase modulation to improve the signal transmission speed, the modulation is not uniquely polyphased, and the number of significant states of modulation is determined according to the noise state of the distribution line. A method for always ensuring the reliability of signal transmission by changing will be described.

FIG. 3 shows an example of the signal format of the carrier signal according to the present invention.

This carrier signal has a guard bit 31, a start bit 32,
It is a phase-modulated signal composed of a modulation significant state number designation bit 33 and a data bit 34.

The guard bit 31 is a signal used for signal arrival detection and phase control of the phase reference signal on the receiving side, and the start bit 32 is a signal used for obtaining phase synchronization necessary for subsequent signal demodulation. is there. The guard bit 31 and the start bit 32 form a synchronous start signal.

The modulation significant state number designation bit 33, which is a feature of the present invention, is a signal that designates the number of significant states of modulation of the data bit 34 which is a data signal following the start bit 32, and is 2 bits in the example of FIG. Is assigned. For example, if the binary signal of the modulation significant state number designation bit 33 is 00, the number of significant states of modulation of the data bit 34 is 2 (two-phase modulation), and if it is 10, the number of significant states is 4 (four-phase modulation). , 01 is designated in advance as 8 (8-phase modulation).

On both the transmitting side and the receiving side, these three signals up to the modulation significant state number designation bit 33 are uniquely subjected to phase modulation / demodulation of two phases.

The number of significant states of modulation of the data bit 34 designated by the modulation significant state number designation bit 33 is changed to 2 phase, 4 phase or 8 phase according to the state of noise distributed on the distribution line at the data transmission side. It That is, a large number of significant states is designated if the state of the distribution line is good, and a small number of significant states is designated if the state of the distribution line is bad. Done by

On the receiving side, the demodulation determination phase number (modulation significant state number) of the subsequent data signal is switched based on the demodulation result of the modulation significant state number designation bit 33.

The data bit 34 is phase-modulated by the sign of the number of significant states designated by the modulation significant state number designation bit 33,
An example of the phase arrangement in that case is shown in FIG.

That is, when the condition of the distribution line is bad, the two-phase modulation is performed as shown in FIG. 9A, and when the condition of the distribution line is good, four-phase modulation is performed as shown in FIG. Alternatively, 8-phase phase modulation is used.

As described above, according to the present invention shown in FIG. 3 and FIG. 4, the data signal transmission rate can be improved according to the noise condition of the distribution line, and the data transmission can be stabilized. In addition, it is possible to efficiently and efficiently.

(Effects of the Invention) As described above, according to the present invention, the carrier signal frequency is set to the harmonic of the commercial frequency of the distribution line or the frequency obtained by dividing the harmonic, and the carrier signal transmitting side and the carrier signal receiving side are received. On both sides, a phase reference signal of the carrier signal frequency is generated from the commercial frequency, and on the transmission side, phase modulation is performed by changing the phase of the phase reference signal according to information,
On the receiving side, the carrier signal received using the phase reference signal is demodulated so that the phase reference signal can be obtained by a simple filter, and the phase shift between the sending side and the receiving side is deviated. Therefore, the circuit configuration for phase modulation / demodulation can be made simple and inexpensive, and stable signal transmission can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a transmission side circuit of a phase modulation / demodulation system embodying the present invention, FIG. 2 is a block diagram showing an example of a reception side circuit of the same, and FIG. 3 is a carrier signal used in the present invention. FIG. 4 is a diagram showing an example of a format, and FIG. 4 is a diagram showing an example of a phase change state when the number of significant states of modulation of a carrier signal used in the present invention is changed. 1 ... Transmission filter, 2 ... Modulation circuit, 3 ... Pulsing circuit, 4 ... Harmonic generation filter, 5 ... Pulsing circuit, 6 ... Dividing circuit, 7 ... Phase reference signal filter, 8
...... Band filter, 11 …… Band filter, 12 …… Carrier detection filter, 13 …… Pulsing circuit, 14 …… Harmonic generation filter, 15 …… Pulsing circuit, 16 …… Division circuit, 17
...... Phase reference signal filter, 18 ...... Phase control circuit, 19 ...
… Demodulation control circuit, 20 …… Multiplier circuit, 21 …… Reception filter, 31 …… Guard bit, 32 …… Start bit, 33…
… Modulation significant number designation bit, 34 …… Data bit.

Claims (1)

[Claims] 1. A carrier signal frequency is set to a frequency obtained by a harmonic of a commercial frequency of a distribution line or a frequency division of the harmonic, and the carrier signal is transmitted from the commercial frequency to the carrier signal on both the transmitting side and the receiving side of the carrier signal. Generate a phase reference signal of the frequency, on the transmission side, performs phase modulation of the carrier signal by changing the phase of the phase reference signal according to the information, on the reception side,
A distribution line carrier signal phase modulation / demodulation method for demodulating a carrier signal received using the phase reference signal.