JPH0344125A - Power line carrier communication equipment - Google Patents

Abstract

PURPOSE:To attain communication whose synchronization is made stable by applying transmission and reception of a test signal so as to attain adaptive synchronization decision level of a synchronizing demodulation circuit in response to noise and phase distortion of a transmission line. CONSTITUTION:The equipment consists of a CSMA communication control block 1, a modulation circuit 2, a driver circuit 3 with a variable attenuator, a coupling circuit 4, a receiver circuit 5, a band pass filter 6, a synchronizing demodulation circuit 7, a pseudo random code generator 8, and a bus test control block 9 and connects to a transmission line 11 being a power line through the coupling circuit 4. Then the transmission power is attenuated in a rate corresponding to a communication signal loss in the transmission line to send the test signal and the relative phase between a modulation pseudo random code and a demodulation pseudo random code is varied at the reception of the test signal to vary a synchronization acquisition discrimination level of correlation demodulation at the communication in response to the correlation demodulation characteristic of the test signal. Thus, the synchronization is made stable at demodulation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power line carrier communication device, and more particularly to a power line carrier communication device such as a Baum bus.

[Conventional technology]

Conventionally, as this type of power line carrier communication device, there is a direct spread spectrum modulation type (see Institute of Electronics and Communication Engineers study group material 5E83-116).

A conventional power line carrier communication device using direct spread spectrum modulation will be described with reference to FIG.

Transmission data is serially input to the modulation circuit 2 from the terminal TXD. The transmission data is multiplicatively modulated in the modulation circuit 2 using a pseudorandom code sequence that is the output of the code generator 8.

The output of the modulation circuit 2 is power amplified by a driver circuit 3A, and then a coupling circuit 4 consisting of a transformer and a capacitor.
The signal is sent out to a transmission line 11 such as a power line.

On the other hand, the transmission line 1 is
The received signal sent to the receiver circuit 1 is inputted to the receiver circuits via the four-coupling circuit 4, amplified, and then inputted to the synchronization/demodulation circuit 7 via the bandpass filter 6.

In the synchronization/demodulation circuit 7, the received signal is subjected to correlation demodulation using a pseudorandom code sequence output from the code generator 8. The synchronization/demodulation circuit 7 uses a delay lock loop to search for a pseudorandom code phase and perform 1~racking.

[Problem to be solved by the invention]

In the conventional power line carrier communication device described above, the transmission line 11
Since a power line such as a light line is used as a power line, there is a drawback that synchronization tends to become unstable during demodulation due to noise generated in the power line.

An object of the present invention is to provide a power line carrier communication device with stable synchronization during demodulation.

[Means to solve the problem]

The power line carrier communication device of the present invention includes a modulation circuit and a driver circuit that performs spread spectrum modulation on transmission data and sends it to a transmission line, a receiver circuit and a synchronization/demodulation circuit that correlates and demodulates a received signal from the transmission line, and a circuit for generating pseudo-random code sequence signals for modulation and demodulation,
means for transmitting a test signal by attenuating the transmission power at a rate corresponding to the communication signal loss in the transmission line; and changing the relative phase of the modulation pseudo-random code and the demodulation pseudo-random code when receiving the test signal. and means for changing the synchronization compensation determination level of correlation demodulation during communication according to the correlation demodulation characteristics of the test signal.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a first embodiment of the present invention.

This embodiment shows a C3'MA type direct spread spectrum power line carrier communication device, in which a CSMA communication control block 1
．． Modulation circuit 2. Driver circuit with variable attenuator 3. Coupling circuit 4. Receiver circuit, bandpass filter 6, synchronization/demodulation circuit 7. Pseudo-random code generator8. It consists of a bus test control block 9 and is connected to a power line transmission line 11 by a coupling circuit 4.

Next, the transmission line test function of this embodiment will be explained.

Referring to FIG. 2, first, C3MA communication control block l outputs test data b in synchronization with clock a.

In the code generator 8, the code length is 1, which is a pseudo-random code.
A modulated output d is generated by generating an m-sequence code C of 17 II and performing direct spread spectrum pi-phase modulation in the modulation circuit 2.

The output power of the modulated output d is adjusted by a driver circuit 3 with a variable attenuator, and outputted to a transmission line 11 of a power line via a coupling circuit 4.

On the other hand, high-level noise is generated from various electrical devices connected to the transmission line 11, and the noise is superimposed on the output of the driver circuit 3 and input to the input of the receiver circuit 5. (Reference: High Frequency
Noise Power Spectrum, Impedance and Transmission Loss on Power Line
In Japan On Intrapil Dink Powerline Communications IEEEE (H
igh Frequency No.1se Po
wer Spectrum, Impedance
and TransmissionLoss of
Power Line in Japan
on IntrabuildingPower L
(In Communications IEEE) Vol. CE-34, No. 2, May 1988) The output of the receiver circuit 5 is filtered to a low frequency by a bandpass filter 6, and then demodulated by a synchronization/demodulation circuit 7.

In the above test signal sending state, by gradually changing the phase of the modulation m-sequence and the demodulation m-sequence output from the code generator 8, as shown in FIG. Curves e, f, and g of phase-correlation characteristics are obtained.

The phase-correlation characteristic curve e is an ideal case where there is no noise in the transmission line 11 and there is no phase distortion in the transmission system up to demodulation due to modulation, but if the noise is large, the correlation value peaks or the curve becomes small f, when there is distortion in the transmission system, the correlation value exhibits a characteristic of curve g having multiple peaks.

The bus test control block 9 sets the synchronization determination level to a value B when the correlation value characteristic is a curve f according to the state of the transmission line 11.
In the case of curve g, the value is set to A.

FIG. 4 is a block diagram of a second embodiment of the invention.

A received signal is input to the receiver circuit 5 from the transmission line 11 via a coupling circuit 4A separate from the driver circuit R3.

The output of the receiver iY35 is input to the synchronization/demodulation circuit 7 via a variable equalizer 61 controlled by the bus control test block 9A.

In this embodiment, the test signal generated in the same manner as in the first embodiment passes through the transmission line 11 once like a normal communication signal, so that it is possible to obtain a reception output that reflects the phase distortion in the transmission line 11. I can do it.

When the bus test control block 9A has a plurality of peaks shown in the phase-correlation value characteristic curve e in FIG. There is an advantage that more stable communication can be performed even when .

〔Effect of the invention〕

As explained above, the present invention transmits and receives test signals and adapts the synchronization determination level of the synchronization/demodulation circuit according to the noise and phase distortion of the transmission line.
This has the effect of making it possible to perform communication with stable synchronization.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the first embodiment of the present invention, Fig. 2 is a signal waveform diagram of each part of the first embodiment, and Fig. 3 is an m-sequence diagram for modulation and demodulation of the first embodiment. FIG. 4 is a block diagram of a second embodiment of the present invention, and FIG. 5 is a block diagram of an example of a conventional power line carrier communication device. DESCRIPTION OF SYMBOLS 1... C3MA communication control block, 2... Modulation circuit, 3, 3A... Driver circuit, 4, 4A... Coupling circuit, 5... Receiver circuit, 6... Bandpass filter, 7 ...Synchronization/demodulation circuit, 8...Code generator, 9
...Bass test control block, 61...Variable equalizer, 100. 100A, 100B, 101...
Power line carrier communication device, 11...transmission line.

Claims (1)

[Claims] A modulation circuit and a driver circuit that perform spread spectrum modulation on transmission data and send it to a transmission line, a receiver circuit and a synchronization/demodulation circuit that correlate and demodulate the received signal from the transmission line, and a pseudorandom code sequence signal for modulation and demodulation. generating circuit, means for transmitting a test signal by attenuating the transmission power at a rate corresponding to the communication signal loss in the transmission line, and a pseudo-random code for modulation and a pseudo-random code for demodulation when receiving the test signal. A power line carrier communication device comprising: means for changing the relative phase of a code; and means for changing a synchronization correction determination level of correlation demodulation during communication according to correlation demodulation characteristics of a test signal.