JPH077925B2 - Distribution line carrier signal transmission method using differential phase modulation - Google Patents

Description

TECHNICAL FIELD The present invention uses a distribution line (power line) as a signal transmission medium, and transmits a control signal in a supervisory control system such as load control and switch control, as well as automatic meter reading. The present invention relates to a signal transmission method using differential phase modulation that can be used for data transmission in a system or the like.

(Prior Art) Conventionally, in information transmission using a distribution line, there are many harmonics of a commercial frequency when a signal is extracted from the distribution line. Therefore, a narrow band filter is used to increase the signal-to-noise ratio. A method of extracting and receiving a signal has been used. However, when the signal passes through the narrow band filter, the rise time of the signal becomes long and the waveform is distorted, so that the signal transmission speed is very slow at about several bits / second.

(Problems to be Solved by the Invention) An object of the present invention is to provide a distribution line carrier signal transmission system that solves the problems of the above-mentioned conventional techniques and dramatically increases the signal transmission speed.

(Means for Solving the Problem) According to the distribution line carrier signal transmission method of the present invention, the transmission signal is transmitted to the transmission side at 1 / n of the commercial frequency f of the power transmitted through the distribution line (n is a positive integer). When the serial data to be transmitted is the first binary bit, it is set as the speed and the carrier frequency is set to m / 2 times the frequency (m is a positive integer). A phase modulating means that inverts the modulation phase to the opposite of the modulation phase and does not invert the modulation phase when the serial data to be transmitted is the second binary bit, and a modulated carrier wave modulated by the phase modulating means A transmitter having an injection means for injecting into

On the receiving side, the extraction means for extracting the modulated carrier from the current flowing through the distribution line, the modulated carrier is delayed for one bit period, and the difference between the delayed modulated carrier and the unmodulated carrier is calculated to obtain the differential signal. There is provided a receiver having differential demodulation means for outputting a demodulated carrier signal and Fourier demodulation means for performing Fourier demodulation of data from the operation-demodulated carrier signal.

Specifically, when m is set to an even number, the first binary bit can be associated with a “mark” and the second binary bit can be associated with a “space”.
In that case, the subtraction circuit is used to calculate the difference between the delayed modulated carrier wave and the unmodulated modulated carrier wave on the receiving side.

In addition, when m is set to an odd number, the first binary bit can be associated with a "space" and the second binary bit can be associated with a "mark". Also in that case, the subtraction circuit is used to calculate the difference between the delayed modulated carrier wave and the unmodulated modulated carrier wave on the receiving side.

Further, when m is set to an odd number, the first 2
It is also possible to associate the binary bit with a "mark" and the second binary bit with a "space". And
In that case, the calculation of the difference between the delayed modulated carrier wave and the non-delayed modulated carrier wave on the receiving side is configured by an adder circuit.

(Operation) As described above, the present invention is configured to perform differential phase modulation for transmission on the transmission side and perform differential demodulation on the reception side. The carrier wave is converted into an amplitude-modulated signal having a double amplitude, and the signal is reproduced by applying Fourier demodulation to this amplitude-modulated signal, so that high-speed and reliable transmission can be realized.

(Embodiment) FIG. 1 shows an embodiment of a transmitting device in a distribution line carrier signal transmitting device of the present invention, and FIG. 2 shows waveforms of respective parts thereof. In this embodiment, the commercial frequency f is 60 Hz, n = 1,
This is an example of performing differential phase modulation by setting m = 17 (that is, an odd number).

The transformer 2 that lowers the low voltage 220V of the pole transformer 1 to a further low voltage 6V, and a 60Hz rectangular wave that is shaped according to the wave number of the commercial frequency (point a voltage in Fig. 2) that is output and is synchronized with the commercial frequency Commercial frequency synchronizing pulse generator 3 for generating synchronizing pulse (point b in FIG. 2), its output and information code input c
The serial data generator 4 generates 60 bps serial data (voltage at point d in FIG. 2) which causes a rising pulse when the information code is in space, and a carrier wave (FIG. 2e).
When the serial data to be transmitted based on the output of the serial data generator 4 is the first binary bit (“space” in this embodiment), it is inverted to the modulation phase opposite to the modulation phase of the previous bit, Phase that generates a phase-modulated wave (FIG. 2f) that is phase-modulated so that the modulation phase remains as it is when the serial data to be transmitted is the second binary bit (“mark” in this embodiment). A modulated wave generator 5 and a commercial frequency zero-cross phase corrector 6 which corrects the waveform by inverting the phase of the latter half of each 1-bit period by using the zero-cross of the synchronizing pulse b (FIG. 2g). It is composed of a switching transistor 7 whose conduction and non-conduction are controlled by its output, and a rectifier 9 which opens and closes the voltage through a switching resistor 7 through a load resistor 8 to pass a load current (FIG. 2h).

Next, the operation of the transmitting apparatus using the differential phase modulation of the present embodiment configured as described above will be described.

The low voltage side (220v) of pole transformer 1 is further transformed by transformer 2.
It is stepped down to 6V (Fig. 2a), and the commercial frequency synchronizing pulse generator 3 takes a zero cross of the output of the transformer to generate a 60 Hz synchronizing pulse synchronized with the commercial frequency. In the serial data generator 4, according to the input information code (60 bps, FIG. 2c), when the information code is a space, the data pulses d1 and d synchronized with the above-mentioned synchronization pulse.
2 (Fig. 2d) is generated.

As shown in FIG. 3, the phase-modulated wave generator 5 includes a voltage follower 51 that allows a carrier wave to pass through in its original phase, an inverter 52 that inverts the phase of the carrier wave, and an output of these voltage follower 51 and an output of the inverter 52. It comprises a switch circuit 53 for selecting and outputting one, and a D flip-flop 54 connected to the control terminal of the switch circuit 53. The data pulse d is input to the clock terminal K of the D flip-flop 54,
A data pulse d is applied, and the d flip-flop 54 is inverted every time the data pulses d1 and d2 are generated (FIG. 2F).
F). The Q output causes the switch circuit 53 to alternately switch and select the output of the voltage follower 51 and the output of the inverter 52, and output the modulation signal f.

The commercial frequency zero-cross phase corrector 6 generates a signal g having a waveform obtained by inverting the phase of the latter half of each 1-bit period of the output f of the phase modulation wave generator 5 based on the output b of the commercial frequency synchronization pulse generator 3. To do. The output signal g controls conduction and non-conduction of the switching transistor 7, and according to the control, a load current h flows to the load resistor 8 via the rectifier 9 and this current flows via the pole transformer 1 to the distribution line. Is injected into. In this embodiment, the load current is controlled by the switching transistor 7 for signal injection, which is very simple and useful. However, since the signal current is directly opened / closed during switching, electromagnetic waves are emitted. Can cause harmonic noise and the injected signal will be modulated at the commercial frequency. In order to avoid such a problem, it is preferable to use an injection device having a resonance circuit composed of a coupling transformer and a resonance capacitor.

FIG. 4 is a block diagram showing the configuration of the receiving device arranged at the substation (receiving side) in this embodiment.

The signal current arriving through a high-voltage distribution line as a transmission line flows into the high-voltage bus, but a main current transformer 11 is inserted in the middle of the signal current, and an auxiliary current transformer 12 is further inserted in the secondary circuit of the main current transformer 11. Load resistance 13 of the secondary winding circuit of the current transformer 12
The voltage generated by is input to the reception filter 14. The reception filter 14 removes the commercial frequency and its harmonic noise components, extracts the signal carrier, and amplifies it to an amplitude of about 1V. The output of the reception filter 14 is input to the differential demodulator 15. Differential demodulator 15
Is a delay element 151 of a baud rate time delay for delaying a signal of one bit period as shown in FIG.
The subtraction circuit 152 is configured to subtract the baud rate time delay signal of the delay element 151 from (t). The differential phase modulation signal u (t) input to the differential demodulator 15 as shown in FIG.
When the baud rate time delay signal v (t) is subtracted from, when the data is a mark, the amplitudes of both signals are added to give a large amplitude signal, but when the data is a space, the amplitudes of both signals are subtracted and the amplitude is decreased. Is 0. Such differential demodulation increases the S / N ratio. The differential demodulation output signal y (t) shown in FIG. 6 is converted into an amplitude modulation signal, and this amplitude modulation wave Asinωt is the reference sine wave signal Bsin (ωt + φ) in the Fourier demodulator 16 of FIG. ) And the reference cosine wave signal Bcos (ωt + φ) are cross-correlated and Fourier demodulated.

FIG. 7 shows the structure of the Fourier demodulator. The output signal Asin ω t of the differential demodulator 15 is input to the two multipliers 26 and 27. In the multiplier 26, the reference cosine wave Bcos (ω that has the same frequency as the input signal frequency generated by the reference cosine wave generator 28
t + φ) and outputs the sinφ component of the signal amplitude.

On the other hand, the multiplier 27 multiplies the reference sine wave Bsin (ωt + φ) generated by the reference sine wave generator 29 to obtain the signal amplitude co
Output the sφ component.

The output of the multiplier 26 is a composite wave of AC and DC components of double frequency, and is alternately integrated by the integrators 36 and 37 for 1 bit time through the analog switches 32 and 33 that alternately open and close for each 1-bit signal Output only the components. The outputs of the two integrators 36 and 37 are added together, and a series of pulse code signal wave amplitudes sinφ
Output the component.

Similarly, the output of the multiplier 27 passes through the analog switches 34 and 35 that alternately open and close bit by bit, and the integrators 38 and 39 alternately output the cosφ component of the signal amplitude for 1 bit time, and the adder 41 adds them. Outputs the cos φ component of the signal wave amplitude.

The sin φ component output from the adder 40 and the cos φ component output from the adder 41 are respectively squared by the squarers 42 and 43 and added by the adder 44 to output the squared value of the absolute value of the signal amplitude. That is, the square value of the signal frequency amplitude is output for the mark of the information pulse code, and 0 V is output for the space because there is no signal frequency.

The code regenerator 17 shapes the signal demodulated by the Fourier demodulator 16 to regenerate the code code.

FIG. 8 shows an example of the waveform of the result of the actual transmission test performed on the receiving device, and is a waveform diagram showing the output of the reception filter, the output of the differential demodulator, and the output of the Fourier demodulator in FIG. Is. It can be seen that a good demodulation result without error is obtained by the combination of differential demodulation and Fourier demodulation.

FIG. 9 shows an example of a signal injection device using an LC resonance circuit which can be used in place of the signal injection device composed of the switching transistor 7, the load resistor 8 and the rectifier 9 in FIG. LC resonant circuit consisting of loosely coupled transformer T and resonant capacitors C1 and C2, and resonant capacitor C
A power supply consisting of a rectifier and a rectifying capacitor for charging 1 and an electronic switch for charging the resonant capacitor C1 from the power supply under the control of the differential phase modulation signal.
SW1 and a switching circuit having an electronic switch SW2 for discharging charge from the resonant capacitor C1. The LC resonance circuit is adjusted to have a resonance frequency centered on the carrier frequency of the differential phase modulation signal. Opening and closing of the two electronic switches of the switch circuit are controlled by a differential phase modulation signal (signal f in FIG. 2), but control signals of opposite phases are supplied to the control terminals of both electronic switches. Therefore, the capacitor C1 alternately operates according to the signal f, and the capacitor C1 repeats charging and discharging alternately, so that the component of the differential phase modulation signal is injected into the high voltage distribution line. In this example, since it has a resonant circuit using a loosely coupled transformer,
It is possible to realize efficient signal injection.

(Effect of the Invention) Conventionally, in this type of distribution line carrier signal transmission method, in order to avoid the influence of harmonic noise of the commercial frequency, which accounts for most of the transmission line noise, the receiving device extracts the signal with a narrow band filter. Was there. However, when a narrow band filter is used, the rise time of the filter becomes long and the waveform is also distorted, so that the signal speed is limited and a low speed of several bits per second is forced.

According to the present invention, all of these conventional problems can be solved. That is, according to the present invention, by performing differential phase modulation and performing differential demodulation on the receiving side, harmonic noise in the transmission path is removed, a narrow band filter is not required, and the signal carrier wave is doubled. S / in converted form to amplitude-modulated signal
The N ratio becomes excellent, and the signal is reproduced by performing Fourier demodulation on this amplitude modulation signal, so that high-speed and reliable transmission can be realized.

[Brief description of drawings]

FIG. 1 shows an embodiment of a transmitting device in a distribution line carrier signal transmitting device of the present invention, and FIG. 2 shows waveforms of respective parts thereof. In FIG. 1 (a), information codes are spaces, marks, spaces, An example of a mark is shown, and FIG. 9B shows an example of the information code being a space, a space, a mark, and a mark. FIG. 3 is a diagram showing an example of the configuration of the phase modulation wave generator. FIG. 4 is a diagram showing a block configuration of a receiving device arranged at a substation (receiving side) in this embodiment. FIG. 5 is a diagram showing an example of the differential demodulator, and FIG. 6 is a diagram showing waveforms of respective parts thereof. FIG. 7 is a diagram showing the structure of the Fourier demodulator. FIG. 8 is a diagram showing waveforms at various parts of the receiving apparatus shown in FIG. FIG. 9 is a diagram showing an example of a signal injection device using an LC resonance circuit. 1 ... pole transformer, 2 ... transformer, 3 ... commercial frequency synchronizing pulse generator, 4 ... serial data generator, 5 ... phase modulated wave generator, 6 ... commercial frequency zero cross phase correction vessel,
7 ... Switching transistor, 8 ... Load resistance, 9
...... Rectifier, 11 …… Main current transformer, 12 …… Auxiliary current transformer, 13 …… Load resistance, 14 …… Reception filter, 15 …… Differential demodulator, 16 …… Fourier demodulator, 17 ...... Code regenerator.

Claims (3)

[Claims] 1. The transmission side sets a transmission signal transmission rate at 1 / n (n is a positive integer) of the commercial frequency f of the power transmitted through the distribution line, and m / 2 times the transmission rate (m Is a positive integer) is used as the carrier frequency, and when the serial data to be transmitted is the first binary bit, it is inverted to the modulation phase opposite to the modulation phase of the previous bit and should be transmitted. Provided is a transmitter having a phase modulator that does not invert the modulation phase when the serial data is the second binary bit, and an injector that injects the modulated carrier wave modulated by the phase modulator into the distribution line. , Extracting the modulated carrier from the current flowing through the distribution line, delaying the modulated carrier for one bit period, and
It has a differential demodulation means for calculating the difference between the delayed modulated carrier wave and a non-delayed modulated carrier wave, and outputting a differentially demodulated carrier wave signal, and a demodulation means for Fourier demodulating data from the differentially demodulated carrier wave signal. A distribution line carrier signal transmission method using differential phase modulation, which is equipped with a receiver. 2. The injection device comprises a rectifier connected to the low voltage side of a pole transformer, a load resistor connected to the rectifier, and switch means for opening and closing a current flowing through the load resistor by a differential phase modulation signal. A distribution line carrier signal transmission method using differential phase modulation according to claim (1). 3. The LC injection circuit, wherein the injection device is composed of a loosely coupled transformer and a resonance capacitor, a power supply circuit for applying a DC voltage to the LC resonance circuit, and a DC voltage from the power supply circuit to the LC resonance circuit. A distribution line carrier signal transmission method using differential phase modulation according to claim 1, further comprising a switch circuit for controlling application by a differential phase modulation signal.