JPH0446422A - Distribution line carrying communication system for spread spectrum signal - Google Patents

Abstract

PURPOSE:To attain high speed data transmission and high reliability by injecting a signal subject to spread spectrum modulation to a distribution line at a sender side, and applying frequency shift demodulation to a spread spectrum inverse modulation signal at a receiver side. CONSTITUTION:A narrow band FSK modulation signal is inputted to a spread spectrum SS modulator 3 at a sender side, and the modulator 3 applies PSK modulation and broad band SS modulation to the signal via a sender side clock generator 33, a PN code generator 32 and a sender side multiplier 31. Then the signal subject to SS modulation is amplified by an injection amplifier 4 and the result is injected to a distribution line through a sender side coupler 5. Moreover, a reception signal is inputted to an inverse spread spectrum modulator 8 at a receiver side, in which the signal is subject to spread spectrum inverse modulation and the result is demodulated by an FSK demodulator 9. Thus, high speed transmission with excellent noise immunity and high reliability is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a spread spectrum power distribution line carrier communication system that utilizes a high voltage power distribution line as a data transmission path.

<Prior art and problems to be solved by the invention> Conventionally, when transmitting data using high-voltage distribution lines, frequency shift modulation or amplitude modulation has been adopted.
When transmitting data using power lines or electric light lines, a spread spectrum communication method has recently been put into practical use.

In this communication method, the transmitting side transmits a narrowband data signal by spread spectrum modulation over a wide band using a pseudo-noise code, and the receiving side demodulates the narrowband signal by despreading the signal. In recent years, it has been gaining popularity as it has excellent noise resistance and is less susceptible to harmonics of commercial frequencies.
It is attracting attention as a very effective communication method.

However, with conventional frequency shifting or amplitude modulation methods, the maximum band that can be used for communication is 60 Hz due to the presence of high levels of 60 Hz harmonics of the commercial frequency on power distribution lines.
It is not possible to ensure 0HzL. Generally, in order to perform transmission at a transmission rate (information rate) of N [bps], N
A signal band of [Hz] is required. That is, if the original signal serving as a carrier wave is modulated Nc times/second, the modulated signal will spread over a band of NCHz). Therefore, a filter that removes 60Hz harmonics cannot be expected to have very sharp characteristics, and in the case of the line-to-line injection method that uses two parallel wires of a distribution line as a transmission path, the signal band that can be secured is about 30Hz. , the transmission speed is 20~3
The maximum speed was around 0 bps, which was a bottleneck in terms of improving transmission speed. Furthermore, due to the direct influence of sudden noise and the like, the transmission quality is currently not very reliable, with a polling retry rate of about 0.1 (about BERIO-'). Furthermore, the power of the signal injected into the transmission line needs to be relatively large, resulting in a problem that the signal injection equipment becomes large.

Therefore, it is desired to increase the speed and reliability of data transmission by applying a spread spectrum communication method to high-voltage power distribution lines, but the current situation is that this has not yet been put into practical use.

<Means for Solving the Problems> In order to solve the above problems, in the present invention, in a power distribution line carrier communication system that transmits information signals using power distribution lines, the transmission side transmits the information as information modulation. The signal is frequency shift modulated, the information modulated signal is phase shift modulated using a fixed form code, the spread spectrum modulated signal is injected into the distribution line, and the receiving side receives a signal with the commercial frequency component removed from the received signal. The present invention is characterized in that the information signal is demodulated by performing phase shift modulation and spectrum despread modulation using the fixed form code, and further frequency shift demodulating the spectrum despread modulation signal as information demodulation.

<Embodiment> FIG. 1 is a block diagram showing an embodiment of the spread spectrum distribution line carrier communication system of the present invention, and FIG. 2 is a block diagram showing an embodiment of the spread spectrum despread modulator of the present system. FIGS. 3(a) to 3(g) are respective signal waveform diagrams of each part in the block of this embodiment.

First, on the transmitting side, as shown in FIG.
A frequency shift (hereinafter referred to as FSX) modulator 2 that performs information modulation is manually operated to set the center frequency to 1080 Hz, for example, as shown in FIG. 3(b).

fl-930Hz, f2-1 with a bandwidth of 300Hz
230Hz FSK modulation is performed, and Saranico's narrowband information modulation signal is spread spectrum (hereinafter referred to as SS).
The signal is input to the modulator 3.

The SS modulator 3 includes a transmitting side multiplier 31 . It is composed of a transmitting side fixed form code generator 32 and a sending side clock generator 33, and the sending side fixed form code generator 32 generally has a maximum code length of 2° to 1 bit, where n is the number of stages of the shift register. Here, for example, a 5-stage shift register is used to generate, for example, a pseudo-noise code (hereinafter referred to as
(called PN food).

SS modulator 3 has a signal transmission characteristic of 10 on high voltage distribution lines.
~20 kHz is good, so the high clock frequency generated by the transmitter clock generator 33, e.g.
．． The PN code shown in FIG. 3(c) output by the PN code generator 32 generated by a 785 kHz clock signal and the above-mentioned FSX modulation signal are transmitted to the transmitting side multiplier 31.
is multiplied and the phase shift (hereinafter,
PSK) modulation is performed, and SS modulation is performed in a band determined by the PN code, for example, a wide band of 1.5 to 17.578 kHz, as shown in FIG. 3(d). That is, the output of the PN code generator 32 (Fig. 3 (
When C)) is at H level, a signal that is in phase with the output of FSK modulator 2 (Fig. 3 (b)) is sent out, and when it is at L level, a signal that is in reverse phase with the output of FSK modulator 2 is sent out. is sent.

The SS-modulated signal is amplified by the injection amplifier 4 and injected into the distribution line by the transmitting coupler 5 which blocks the commercial frequency of 60 Hz.

Next, on the receiving side, a receiving side coupler 6 consisting of a signal receiving transformer with a bypass filter connected to the low voltage side converts the received signal of the spread modulation signal from which the 60 Hz and 60 Hz harmonic components of the commercial frequency are removed. is the receiving amplifier 7
The signal is amplified and input to a despread modulator 8 that performs spectrum despread modulation.

The despreading modulator 8 includes a sliding correlation clock generator 81 . Receiving side PN code generator 82° Receiving side multiplier 8
3 and a correlator 84, and inputs the same PN code as that on the transmitting side outputted by the PN code generator 82 and the above received signal to the multiplier 83, and multiplies it to produce a spectrum. Despread modulation is performed, but
If the phase of the PN code on the transmitting side and the phase of the PN code on the receiving side do not match, that is, if they are not synchronized, despread modulation is not performed.

The operation of the above despreading modulator will be described in detail below.

First, when synchronization is not established, the output of a synchronization detector 844 (described later) is below a reference value predetermined in the synchronization state, so the sliding correlation clock generator 81 is selected by the clock switch 841. This clock generator 81 uses a frequency slightly lower than the oscillation frequency of the transmitting side clock generator 33 that generates the transmitting side PN code, for example, 8.659kHz, in order to force the synchronization state at an early stage. Generates a clock signal.

This clock signal is used by three receiving side PN code generators 82a, 82b, 8 which generate the same PN code as the transmitting side.
2C, three types of PN codes 5a to Sc, each shifted by one clock, are generated from PN code generators 82a to 82c each composed of a five-stage shift register. In other words, the PNN code Sc which is one clock phase ahead of the PN code sb at the reference clock phase.
A PN code Sc delayed by one clock is output.

These three types of PN codes 5a-Sb and the above-mentioned received signal are multiplied by multipliers 83a-83c, respectively, and
FSK signal band bandpass filters 842 a to 842 c in which the despread modulated signal constitutes the correlator 94
By passing through absolute value circuits 843a to 843C, correlation outputs of DC level are detected.

If the output of the synchronization detector 844, which is composed of an adder that adds these correlation outputs, is less than the reference value, that is, if synchronization is not yet achieved, the clock signal with a slightly lower frequency than that of the transmitting side is used as described above. , receiving side PN
If the so-called sliding state in which the codes shift little by little continues, and from this sliding state, any one of the three codes becomes synchronized with the received signal, that is, the output of the synchronization detector 844 becomes equal to or higher than the reference value. The search process is stopped, and in order to maintain synchronization, the voltage controlled oscillator 846 is selected by the clock switch 841, and the PNN code ScS, which is phase advanced and phase delayed as described above, is selected.
A correlation discriminator 84 configured with a subtracter that subtracts the correlation outputs from the absolute value circuits 834a and 834c corresponding to c.
The output of 5 is input to voltage controlled oscillator 846. This voltage controlled oscillator 846 is a correlation discriminator 8 when the PN code sb at the reference phase and the received signal are synchronized.
Based on the output of 45, the clock frequency of the transmitter is 8.7
The oscillation frequency is adjusted to be the same as 85kHz.

Now, if the phase-advanced PNN code Sc received signal matches the voltage controlled oscillator 846 whose oscillation frequency changes according to the input terminal, + side control is applied and the oscillation frequency is lower than 8.785kHz. PN rose and lagged again
When the code Sc and the received signal match, the - side control is lowered and the frequency becomes lower than 8.785 kHz. In this way, feedback control is performed until it matches the reference PN code sb, and a PN code that is in phase with the transmitting side PN code as shown in FIG. 3(e) is generated, and synchronization is maintained.

At this point, the output of the PN coco generator 82b (Fig.
When e)) is at H level, the SS modulation signal (
The receiving side multiplier 83b sends out a signal in phase with that shown in FIG. 3(d)), and when it is at L level, sends out a signal in reverse phase, which performs despread modulation as shown in FIG. This despread modulated signal is sent to an FSK demodulator 9 that demodulates information, which is provided corresponding to the FSK modulator 2 on the transmitting side.
is input.

The FSK demodulator 9 is composed of an FSK demodulation amplifier 91 and a phase-locked loop (PLL) detector 92, and the phase is determined by the detector 92 and the result shown in FIG.
A binary data or information signal as shown in g) is demodulated.

In the above embodiments, the information modulator/demodulator is an FSK modulator/demodulator, but a phase shift (PSK) modulator/demodulator or a quadrature phase shift (QPSK) modulator/demodulator may be used. However, the bandpass filters 842a to 842C in the correlator 84 of the despreading modulator 8 need to be changed to filters with corresponding bands.

<Effects of the Invention> As described above, according to the present invention, it is possible to perform highly reliable transmission with excellent noise resistance, and the transmission speed is approximately 10 times that of the conventional method (200 to 300 bps). In addition, high-quality transmission is achieved, with the polling retry rate representing transmission quality being approximately zero (BERlo-6).

Furthermore, since the injection power is reduced, the transmission equipment can be made significantly more compact and the cost can be reduced.

Furthermore, the practical use of data transmission using the spread spectrum communication method on high-voltage power distribution lines has great practical value.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the spread spectrum distribution line carrier communication system of the present invention. FIG. 2 is a block diagram showing an embodiment of a spectrum despread modulator of this method. FIGS. 3(a) to 3(g) are respective signal waveform diagrams of each part in the block of this embodiment.

Claims (1)

[Claims] In a distribution line carrier communication system that transmits information signals using distribution lines, the transmission side performs frequency shift modulation on the information signal as information modulation, and then phase shift modulates the information modulated signal with a fixed form code to spread spectrum. The modulated signal is injected into the power distribution line, and on the receiving side, the signal obtained by removing the commercial frequency component from the received signal is subjected to phase shift modulation using the fixed form code, spectrum despread modulation, and then the despread spectrum modulated signal is used as information demodulation. A spread spectrum distribution line carrier communication system in which the information signal is demodulated by frequency shift demodulation.