JPS60162326A - Power line communication system of spread spectrum multiple access and transmitter-receiver - Google Patents

Abstract

PURPOSE:To attain data transmission system with high quality and at a high speed via a power line by superposing the synchronizing pseudo random series onto the signal which gave the spread spectrum modulation to the address and data of the remote side via a pseudo random series and transmitting these superposed signal and series to the power line. CONSTITUTION:The level of a high frequency signal received via a coupling circuit 500 and sent from a line is detected by a power detecting circuit 506. When this level is less than the prescribed value, a gate 510 is opened. Then a generator 514 for synchronizing pseudo random series P0 with a transmission request signal sent from a terminal. The series P0 is transmitted with a transmission clock. At the same time, a timer 513 is started to actuate a generator 511 for modulated pseudo radom series P1 after a time T0 elapses. The address and data information on the remote side sent via a signal line 563 are multiplied 512 for spread spectrum modulation. This modulated signal is added 515 with the series P1 given from the generator 511, and this addition signal is amplified 502 and transmitted to a power line via the circuit 500. In a reception mode a synchronizing signal series P0 is detected by a synchronizing signal extracting circuit 503. While the series P1 is detected by a generator 504 for demodulation pseudo random series and undergoes the reverse spread spectrum demodulation 505.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application in Childcare) The present invention relates to a communication system in which a plurality of transmitting and receiving devices exchange information signals via a power line.

(Prior Art and its Problems) Conventionally, modulation methods have been used for transmitting information signals via power lines, and frequency modulation methods or phase modulation methods have been adopted in the case of power distribution line transmission lines. The high-frequency characteristics of power lines, regardless of whether they are transmission lines or distribution lines, include large corona noise and load noise, and the transmission characteristics also vary greatly depending on the load condition of the power line. In addition, both noise and transmission characteristics fluctuate over a long period of time, a short period of time, and even instantaneously depending on the load condition. An upper limit is set for the signal power so as not to adversely affect other systems. Under such extremely poor transmission path conditions, it is difficult to smooth the transmission characteristics using conventional methods, and it is necessary to lower the signal power in order to lower the signal spectrum density. For this reason, it was difficult to perform highly reliable communications, and in particular, high-speed data transmission was impossible.

(Object of the Invention) An object of the present invention is to eliminate the drawbacks of the above-mentioned conventional methods and to provide a high-quality high-speed data transmission method and a transmitting/receiving device via a power line.

(Structure of the Invention) According to the present invention, in a power line communication system in which a plurality of transmitting and receiving devices transmit information signals via the same power line, when a transmission request occurs on the transmitting side, the received signal power of the power line is detected, If the received signal power is above a certain value, it is assumed that the power line is already in use and the transmission request is rejected, and if it is smaller than a certain value, a pseudorandom sequence for synchronization is first sent, and then the information signal is spread spectrum modulated. On the transmitting and receiving sides, a synchronization signal is extracted from the transmitted pseudorandom sequence for synchronization, and based on the address or pseudorandom sequence for modulation contained in the received information signal, it is determined whether the signal is addressed to the own transmitting/receiving device. A spread spectrum multiple access power line communication system and a transmitting/receiving device are obtained, which are characterized in that the information is determined and if the information is addressed to the transmitting/receiving device, the data information signal is received and communication is performed.

(Principle of the Invention) Spread spectrum communication method spreads the spectrum over a wide band by product modulating a narrowband information signal with a pseudo-random sequence with a high clock frequency and transmits the signal.The receiving side uses correlation detection to detect the received signal. This is a method that demodulates the signal by despreading the spectrum and obtains a high reception SN (signal-to-noise) ratio even under peak power limitations. As a pseudorandom sequence, an m sequence (maximum flame sequence) is often used. This kind of spread spectrum communication is resistant to narrowband noise, resistant to transmission path fluctuations such as fading, etc.
Due to its high level of confidentiality, it has been applied to wireless communications. As for application to wired communications, the scope of application has only been studied with a focus on multiple access using code multiplexing, since the characteristics of wired lines are better than those of wireless circuits. However, the power m is originally intended for the transmission of commercial power signals, and there are almost no regulations regarding high frequency transmission characteristics.

Therefore, as described above, the high frequency transmission characteristics vary greatly depending on the connection state of the electrical equipment, resulting in a poor high frequency line environment even though it is wired. In addition, the negative impact on commercial power signals, which is the original purpose of power lines, must be kept to a minimum.
In order to minimize the impact on electrical equipment, the power of high-frequency signals must also be reduced. As described above using the wireless link example, the spread spectrum communication method can perform good transmission in such a poor high-frequency line environment, but it is also important to minimize the impact on commercial power signals and electrical equipment. Also, in spread spectrum communication, the modulation spectrum is spread over a wide band and in white, so the spectrum density is low and good characteristics are exhibited.

Considering the above, it can be seen that by applying the spread spectrum communication method to power line transmission, it is possible to obtain very useful and novel effects that could not be obtained with conventional methods.

Next, the spread spectrum communication system will be explained with reference to the drawings. FIG. 1 shows the modulation process in the spread spectrum communication system. The modulation process in the spread spectrum communication system involves product modulation of the narrowband information signal shown in Figure 1(a) with a pseudo-random sequence generated at a high clock frequency as shown in Figure 1(b) as an example. It spreads the spectrum over a wide band. Figure 1 (C1) shows an example of a signal waveform subjected to spread spectrum modulation. Figure 2 shows an example of the frequency spectrum of a signal in the spread spectrum modulation process. Figure 2 (a) shows the spectrum of a narrowband information signal. Figure 2 (bl is an example of the spectrum of a pseudo-random sequence, and Figure 2 (C) is an example of a spread spectrum modulation signal. Figure 2 (C) is the main spectrum of the modulated signal spectrum. Only the lobes are shown. Partial spectra 200(]) to 200() in the spread spectrum in FIG.
N) contains the signal components of the narrowband information signal evenly distributed. Here, the period length of the N pseudorandom sequence is shown. In the demodulation process, the received signal is subjected to correlation detection using the same pseudo-random sequence as on the modulation side, and a narrowband information signal having a spectrum of Figure 2 (al) can be obtained from a spread signal having a spectrum of cl (Figure 2). The above-mentioned property that the narrowband information signal is spread evenly has a great effect on communication using a busy power line.The transmission characteristics of a power line vary greatly depending on the load condition, and there is a possibility that multiple zero points may occur. There is also.

Figure 3 (al) shows an example of the transmission characteristics of a power line under a certain load condition. The characteristic in Figure 3 (a) is an example in which a transmission zero point occurs at the frequency position fl. Whether by modulation, frequency modulation, or phase modulation, f
If the frequency l is the center number, the received signal power will be extremely small and the transmission quality will be greatly degraded. On the other hand, according to the spread spectrum power line communication system of the present invention, due to the property that the narrowband information signal is spread evenly, f
, only the signal power near the frequencies of , is lost, so that almost all the signal power is received. This effect becomes more noticeable as the period length N of the pseudorandom sequence increases. Figure 3 (bl, (c) shows the signal spectrum according to the conventional method, and an example of the demodulated spectrum demodulated through the transmission line of Figure 3 (al), Figure 3 (d), (e
The signal spectrum according to the method of the present invention is shown in Fig. 3 (a).
1 shows an example of a demodulated signal spectrum demodulated through a transmission path of 1. In Figure 3 (cl, (el), the dotted line is an example of the transmitted information signal spectrum. Also, the transmission characteristics of the power line vary greatly over time as the load condition changes. That is, the position of the transmission zero point In this situation, according to the conventional method, the received signal power fluctuates greatly over time, and the received signal power decreases rapidly at the time when a zero point exists near the center frequency.) , it is clear that stable communication will be impossible.On the other hand, in the spread spectrum power line communication system of the present invention, even if the transmission characteristics, especially the transmission zero point, changes over time, the received signal power will hardly change. Furthermore, in the method of the present invention, power line noise is whitened during the demodulation process, making it possible to achieve communication that is especially resistant to frequency-selective noise. Also, in order to synchronize,
A pseudo-random sequence for synchronization that is sent out prior to the information signal,
As shown in the present invention, by using a power line as a flag for exclusive use, a system can be obtained in which a power line is shared as a transmission medium among a plurality of terminals, and flexibility in system operation is greatly increased.

As described above, the method of the present invention enables high-speed data transmission using commercial power lines, which was impossible with conventional methods. The spread spectrum multiple access power line communication system of the present invention ensures stable high communication quality by spreading signals and distributing risks in order to minimize the influence of fluctuations in transmission characteristics due to load conditions. By detecting the signal power, a flexible system for sharing the power line between multiple terminals can be obtained, and its effects are significant.

(1! Example) Hereinafter, the present invention will be described with reference to an example for realizing the present invention. FIG. 4 is a diagram showing a power line communication system of the present invention. In the figure, 400 indicates a power line, and 401 (11
~401(K) indicates a transmitting/receiving device. Also, 402+]
) to 402 (M) indicates a terminal tube. 401 (11-40
Each transmitting/receiving device of 1(K) is passively connected to 400 power lines, and in order to communicate between the transmitting/receiving devices, the high frequency signal power of the piezoelectric power line is detected, and if no high frequency signal is detected, a spread spectrum signal is detected. Communication is performed through modulation and demodulation. That is, when observing a certain time, only the - set of transmitting/receiving devices is communicating via the power line. Further, the address of the other party to communicate with can be set by incorporating it into the information data, or by selecting a modulated pseudo-random sequence uniquely assigned to the transmitting/receiving device. With the above-mentioned pressure, the multi-access method can be realized. According to this method, a signal failure may occur, albeit with a very small probability, due to the propagation delay of the power line. Since this failure probability is small for non-ZVC, it is thought that there will be almost no performance deterioration in practical use even if a method of avoiding it by a transmission control procedure between terminals is taken.

FIG. 5 is a block diagram showing an embodiment of a transmitting/receiving device implementing the present invention. Here, to simplify the explanation,
Although we will explain the case where one terminal is connected to one transmitting/receiving device, it is obvious from the following explanation that multiple terminals can be connected to one transmitting/receiving device as shown in Fig. 4. .

500 is a coupling circuit for coupling the power line and the transmitting/receiving device, and the signal line 550 is connected to the power line via an outlet. The coupling circuit 500 separates the low frequency power signal and the high frequency data signal, and the low frequency commercial power signal is supplied to the power supply of the electrical equipment via the signal line 553. First, the operation on the receiving side will be explained with reference to the drawings. The high frequency data signal separated by the coupling circuit 500 is output to a signal line 551 and input to the automatic gain control amplifier 501 . The automatic gain control amplifier 501 has a dynamic range sufficient to compensate for loss fluctuations in the power line.
A signal with constant power is output to signal line 554.

From the signal on the signal line 554, a clock component of the pseudo-random sequence for synchronization and a frame signal of the pseudo-random sequence for demodulation are extracted by the synchronization signal extraction circuit 503 and output to the signal line 555. The time required for synchronization is designed to be less than or equal to a predetermined To. The synchronization signal extraction circuit 503 also detects the signal level of the synchronization signal and outputs it to the signal line 556. This signal level detection function of the synchronization signal is for detecting whether a pseudorandom sequence for synchronization has already been sent to the power line, that is, whether the power line is already being used by another transmitting/receiving device. The demodulation pseudorandom sequence generator 504 receives a clock signal and a frame signal from a signal line 555, and a signal line 557 receives the same pseudorandom sequence as the modulation pseudorandom sequence input to the transmitter/receiver through the power line. Output. The pseudorandom sequence generator is constructed in the usual manner using shift registers and exclusive ma sum gates. The pseudorandom sequence from the signal line 557 and the signal from the signal line 554 are multiplied by the multiplier 505 and outputted to the signal line 558K. A demodulated low-pass data signal component is extracted from the signal on the signal line 558 by a low-pass filter 507 and output as a signal @560. Signal @ 560
The demodulated low-frequency data signal is input to an address verification circuit 508, and it is detected from the address information not included in the demodulated low-frequency data signal whether the data is addressed to this transmitting/receiving device. In the address verification circuit 508, if the data is addressed to this transmitting/receiving device, a logical “1” is sent to the signal line 561.
(t times “0”), and if the data is not addressed to this transmitting/receiving device, logically “θ” (or 1
') is output to the signal line 561. In the gate 509, if the signal on the signal line 561 is "1" (or "0"), it is output to the signal line 562 through the demodulated low-frequency data signal from the signal line 560, and the signal on the signal line 561 is "0" (or "0"). If it is "1"), the demodulated low frequency data signal from the signal line 560 is blocked and is not output to the signal m562. In this way, it is possible to select a transmitter/receiver using the address information in the demodulated low-band data signal. 506 is a power detection circuit that detects the signal power of the pseudo-random sequence for synchronization, which detects the signal power from the signal level of the pseudo-random sequence for synchronization from the signal $ 556, and if this signal power exceeds a predetermined value, If h is smaller than a predetermined value, it sends “0” to the signal line 559, and if h is smaller than a predetermined value, it sends “pi”. Next, the operation of the transmitting side will be explained with reference to the diagram.When a transmission request occurs from the terminal side, the signal line 564
When the signal on the signal line 559 becomes logical K “1”,
If the signal is logically P, i.e., the power line is not being used by any other transmitting/receiving device, the AND gate 510 opens;
Signal @ 565 signal is logically “B”. Signal line 5
When the signal 65 becomes logical K "1", the synchronization pseudo-random sequence generator 514 is activated, and the synchronization pseudo-random sequence is output to the signal line 570 by the transmission clock from the signal line 568.

Moreover, when the signal on the signal line 565 becomes logically "11",
The timer of 513 is activated, and time T has elapsed since it started working.
When o has elapsed, a pulse is output to the signal line 566 to cause the modulation pseudo-random sequence generator 511 to perform one operation. Signal # again! The 566 signal is also notified to the terminal.

Pseudo-random sequence generator for modulation 511H, signal line 56
When the operation start pulse from 6 arrives, a pseudorandom sequence for modulation is output to the signal line 567 using the transmission clock from the signal line 568. On the terminal side, when a transmission request occurs and an operation start pulse arrives via signal line 566,
First send the address of the other party's transmitting/receiving device to the signal line 563, and then send the information data signal to the signal line 563.
Send to. The signal on the signal line 563 is multiplied by the modulation pseudorandom sequence from the signal line 567 in the multiplier 512.
That is, it is spread spectrum modulated and output to a signal line 569.

The signal on the signal line 569 is added to the pseudorandom sequence for synchronization from the signal line 570 in the adder 515, and the signal is added to the signal line 57.
1 is output. The signal on the signal line 571 is transmitted to the amplifier 502.
After being sufficiently amplified, the signal is output to a signal line 552, and then sent to a power line via a coupler 500.

FIG. 6 is a detailed diagram showing one embodiment of a synchronization signal extraction circuit in a transmitting/receiving device that implements the present invention. Fifth
This corresponds to the circuit 503 in the figure. Signal line 554
The output signal from the automatic gain control amplifier from 600,6
Each multiplier pressure of 01 and 602 is input. The 6000 multiplier multiplies the input signal from the signal line 554 and the signal from the signal line 659 and outputs the product to the signal line 651. Multiplier 6
01, the product of the input signal from the signal line 554 and the signal from the signal 9658 is taken and output to the signal line 652. Further, the multiplier 602 multiplies the input signal from the signal line 554 and the signal from the signal line 657, and outputs the resultant product from the signal line 6531C. The signals on the signal lines 657, 658, and 659 are the outputs of the pseudo-random sequence generator 607, and are the outputs of each stage of the shift register in the pseudo-random sequence generator, shifted by one bit. That is, the pseudorandom sequence on signal line 659 is one bit behind the pseudorandom sequence on signal line 658, and the pseudorandom sequence on signal line 658 is one bit behind the pseudorandom sequence on signal line 657. The signal on the signal line 652 is input to a low-pass filter 604, and after extracting only low-frequency components, the signal is passed to the signal line 556K.
Output. The signal on signal line 556 is input to power detection circuit 506 in FIG. 5 as a signal indicating the signal level of the synchronization signal. The signal on signal line 651 and the signal on signal line 653 are subtracted by subtracter 603 and output to signal line 654. The signal on the signal line 654 is output to the signal line 655 after only the low frequency components are extracted by the low pass filter 605 . The signal on the signal line 655 is input as a control signal to the voltage variable oscillator 606, and a clock signal with a frequency corresponding to the voltage level is output as a signal @656. signal line 6
56 clock signals are input to a pseudo-random sequence generator 607. In this way, this circuit forms a loop system and can synchronize the pseudo-random series. The basic part of this circuit is usually called a delay locked loop and is a well-known control system.

The circuit configuration shown in FIG. 6 is a known delay lock-loose circuit to which a multiplier 601 and a low-pass filter 604 for detecting the synchronizing signal level used in the present invention are added. A detailed explanation of the synchronization process will be omitted, but after synchronization is achieved, the pseudorandom sequence from the signal line 658 and the input synchronization pseudorandom sequence from the signal line 554 are exactly the same υ, After all, correlation reception is performed by the multiplication@601 and the low-pass filter 604, and the level of the DC component, that is, the pseudo-random sequence for synchronization, is obtained by spectrum despreading. The signal on signal line 658 is 608
is input to the frame synchronization signal extraction circuit of the signal line 658.
A frame signal is output to the signal line 660 every frame period of the pseudorandom sequence from . Since the pseudo-random sequence on the signal line 658 and the pseudo-random sequence for input synchronization from the signal line 554 are the same, the frame signal on the signal line 660 is the pseudo-random sequence for input synchronization from the signal line 554. This is the frame signal. signal line 66
The zero frame signal and the clock signal from signal line 656 are supplied through signal line 555 to the demodulation pseudo-random sequence generator shown in FIG. The circuit is designed so that the above synchronization process is completed within the time To. After the time To has elapsed, a modulated signal in which the information data signal is spread spectrum-spread on the input signal from the signal line 554 is also input superimposed on the pseudorandom sequence for synchronization, but after synchronization is established, the modulated signal is The signal is high frequency noise and low pass filter 60
4 and 605 can be sufficiently removed.

FIG. 7 is a block diagram showing an embodiment of another transmitting/receiving device implementing the present invention. Since the configuration is almost the same as that of the embodiment shown in FIG. 5, the operation will be explained without repeating the explanation of the overlapping parts. First, the operation of the receiving side will be explained. In this embodiment, each transmitting/receiving device is assigned a fixed and unique pseudo-random sequence as an address, and when transmitting, the uniquely assigned pseudo-random sequence is assigned to the other party's transmitting/receiving device to which the transmission is desired. This method realizes a method of selecting a transmitting/receiving device by modulating information data with a pseudo-random address. Therefore, the demodulation pseudo-random sequence generator 504 receives the initial value signal of the shift register from the 1-signal line 750 in order to generate a pseudo-random sequence uniquely assigned to each terminal. Since correlation reception is performed using the pseudo-dumb/dumb sequence generated by this initial value signal, the low-pass filter 507 outputs only when the modulation pseudo-random sequence on the transmitting side and the demodulating pseudo-random sequence on the receiving side match. The demodulated low frequency information data signal is obtained on the signal line 560 of the signal line 560. Therefore, the address verification circuit 508 and gate 509 shown in FIG. In order to identify the device 'f-, the initial value of the shift register is input as address information to the modulation pseudo-random sequence generator 511 via the signal line 751.The remaining processing is the same as that in FIG. Since there is, I will omit it.

(Effects of the Invention) As described above, a spread spectrum power line communication system capable of accommodating as many as '4I transmitting/receiving apparatuses and allowing multi-access can be achieved through a simple procedure. The multiple-access power line communication method using the spread spectrum communication method is strong against fluctuations in transmission characteristics, strong against frequency-selective noise, and because the modulation spectrum is spread over a wide band and the spectrum density is low, there is no significant negative impact on other equipment. It has the advantage of being able to reduce the amount of energy required, and can be applied to power line high-speed data transmission, which was impossible with conventional methods, and its effects are tremendous.

[Brief explanation of the drawing]

Figure 1 (al, (bl, (cl) is a timing chart showing the modulation process in the spread spectrum communication system, and Figure 2 (a), (bl, (cl) is a timing chart showing the frequency spectrum of the signal in the spread spectrum modulation process. Figures 3 and 3 (al to el are diagrams showing examples of transmission characteristics of power lines and signal spectra of this system and conventional system, and Figure 4 is a diagram showing an example of system configuration in this system. , FIG. 5 is a block diagram showing an embodiment of the transmitting/receiving device in this method, FIG. 6 is a block diagram showing a synchronization signal extraction circuit in the transmitting/receiving device in this method, and FIG. It is a block diagram showing another example of the transmitter/receiver in this system.
1(K), - transmitting/receiving device, 402 (1) to 402(
M)--Terminal, 500--Coupler, soi--Automatic gain control amplifier, 502--Amplifier, 503--
Synchronous signal extraction circuit, 504, 511, 514゜607・
...pseudo random sequence generator, 505,512,600
゜[)1, 602... Multiplier, 506... Power detection circuit, 507604, fi05... Low pass filter, 508... Address matching circuit, 509... Game), 510... AND gate, 513... timer, 515... adder, 606... voltage variable oscillator, 603... subtracter, 608... frame synchronization signal extraction circuit, respectively. Hit the deputy”-”- Shino Hakubi (Fig. 4, Fig. 5)

Claims (4)

[Claims] (1) In a power line communication system in which a number of transmitting and receiving devices transmit information signals via the same power line, when a transmission request occurs on the transmitting side, the received signal power from the power line is detected and the received signal power is is greater than a predetermined value, the power line is considered to be already in use and the transmission request is rejected, and the received signal power is higher than the previous value. 5 If the value is smaller than a predetermined value, a pseudo-random sequence P for synchronization is first generated. is transmitted to the power line after attenuating low frequency components, and after a predetermined period of time has elapsed, the other party's address information and data information signal are spread spectrum modulated using a pseudo-random sequence PI different from the synchronization pseudo-random sequence P0. The signal is superimposed on the synchronization pseudo-random sequence P0 to attenuate low frequency components, and then sent to the power line, and on the receiving side, the input signal from the power line is separated into a commercial power signal and a high frequency spread spectrum signal by a filter, A synchronization signal is extracted from the separated high-frequency spread spectrum signal using the synchronization pseudo-random sequence P0, and spectrum despread demodulation is performed using the pseudo-random sequence P synchronized by the synchronization signal to generate an information signal. ? A spread spectrum multiple access power line communication system characterized in that if the address information contained in the information signal is addressed to the own transmitting/receiving device, the data information signal is received and communication is performed. (2) In a power line communication system in which multiple transmitting and receiving devices transmit information signals via the same power line, when a transmission request occurs on the transmitting side, the power of the received signal from the power line is detected, and the power of the received signal is determined in advance. If the received signal power is greater than or equal to the predetermined value, it is assumed that the power line is already in use and the transmission request is rejected, and if the received signal power is less than the predetermined value, the synchronization pseudorandom sequence P0 is first changed to the low frequency component. After attenuating the signal, it is sent to the power line, and after a predetermined period of time, the data information signal is spread spectrum modulated using a pseudo-random sequence Pn assigned to the other party's transmitter/receiver with which communication is desired. Pseudo-random sequence P. The input signal from the power line is separated into a commercial power signal and a high frequency spread spectrum signal by a filter on the receiving side, and the separated high frequency spread spectrum signal is Extracting a synchronization signal from the signal using the synchronization pseudorandom sequence P0,
A spread spectrum multiple access power line communication system characterized in that communication is performed by despread spectrum demodulation using a random sequence Pn that is uniquely assigned to and similar to a self-transmitting/receiving device synchronized by the synchronization signal. (3) In a power line communication type transmitting/receiving device in which multiple transmitting/receiving devices transmit information signals via the same power line,
a coupling means including a filter for coupling a power line and a transmitting/receiving device and separating a commercial power signal and a high frequency spread spectrum signal; a first amplifying means for amplifying the signal from the nuclear coupling means; and a synchronizing means from the first amplifying means. a synchronizing signal extracting means for extracting the signal and a received synchronizing signal level, a power detecting means for detecting power from the received synchronizing signal level of the synchronizing signal extracting means, and a synchronizing signal extracting means for demodulating the received synchronizing signal. a first pseudo-random sequence generation means for generating a first pseudo-random sequence from a synchronization signal and a clock signal; and a first pseudo-random sequence generation means for multiplying an output of the first pseudo-random sequence generation means and an output of the first amplification means. a multiplier, a low-pass filter for extracting the low frequency component of the output of the first multiplier, and an address for detecting whether the output signal of the low-pass filter is an information signal addressed to the own transmitting/receiving device. detection means, switch means for opening and closing the output of the low-pass filter according to the output signal of the address detection means, and a timer means that is activated when no power is detected by the power detection means when a transmission request occurs. and a second device that generates a second pseudo-random sequence for subtle modulation on the transmission clock that starts operating when a predetermined period of time T0 has elapsed since the timer means was activated.
a second multiplier for multiplying the output of the second pseudo-random sequence generating means by the transmission information data; synchronization signal generation means for generating a third pseudo-random sequence for synchronization using a reliable clock; addition means for adding the output of the synchronization signal generation means and the output of the second multiplier; and the output of the addition means. and second amplifying means for amplifying and transmitting the amplified signal to the power line via the coupling means. (4) In a power line communication type transmitting/receiving device in which multiple transmitting/receiving devices transmit information signals via the same power line,
a coupling means including a filter for coupling a power line and a transmitting/receiving device and separating a commercial power signal and a high frequency spread spectrum signal; a first amplifying means for amplifying a signal from the coupling means; and a synchronizing means from the first amplifying means. a synchronizing signal extracting means for extracting the signal and a received synchronizing signal level; a power detecting means from the received synchronizing signal level of the synchronizing signal extracting means;
a first pseudo-random sequence generating means for demodulation that generates a first pseudo-random sequence uniquely assigned to each transmitting/receiving device in advance using the extracted synchronization signal;
a first multiplier for multiplying the output of the pseudorandom sequence generation means and the first amplification means; a low-pass filter for extracting the low frequency component of the output of the first multiplier; A timer means that is activated when power is not detected by the power detection means when a request occurs; and a transmission clock that starts operating when a predetermined period of time To has elapsed after the timer means was activated. a second pseudo-random sequence generating means for generating a second pseudo-random for modulation that is uniquely assigned to the other party's transmitting/receiving device that desires transmission; and the output of the second pseudo-random sequence generating means and transmission information. a second multiplier for performing multiplication with data; a synchronization signal generation means for generating a third pseudo-random sequence for synchronization using the time transmission clock of the To after the timer means is activated; addition means for adding the output of the synchronization signal generation means and the output of the second multiplier;
and second amplification means for amplifying the adding means and transmitting the amplified signal to the power line via the coupling means.