JP2006186734A - Line state detecting device, communication apparatus, balanced transmission system, and communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a line state detecting device for easily detecting the balance state of a transmission line in a balanced transmission system with excellent precision. <P>SOLUTION: A first transmission apparatus 100 transmits a pilot signal which is generated in a pilot signal generator 14 by a prescribed timing, detects the unbalance component of the transmission line 300 in transmitting the pilot signal by an unbalance component detector 13, and controls a transmission signal so as to reduce the unbalance component by a transmission control unit 12, based on the detected unbalance component. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a line state detection device that detects a state of a transmission line in a balanced transmission system that performs data transmission using a pair of conductors, a communication device including the same, and a balanced transmission system.

  Conventionally, balanced transmission systems that perform data transmission using a pair of transmission lines in a balanced state have been widely used. In this type of balanced transmission system, a transmission line such as a dedicated communication line is often used, such as a telephone line, and a certain degree of balance is usually maintained.

  An example of the transmission part and transmission line of the conventional balanced transmission apparatus is shown in FIG. This balanced transmission device is configured to send a signal from a transmission unit 91 to a transmission line including a pair of conductors W1 and W2 via a transmission transformer T92. At this time, the current of the transmission signal transmitted from the transmission unit 91 depends on the characteristics of the transmission unit 91 and the transmission lines W1 and W2.

  The transmission line from the transmission unit to the reception unit is originally required to be perfectly balanced, but in reality, it is connected to the unbalanced elements in the transmission unit and the reception unit, the wiring conditions of the transmission line, and the middle. In reality, the current flowing through the conductors W1 and W2 of the transmission line is not completely balanced. When the current flowing through the transmission line is unbalanced in this way, a part of the transmission power leaks from the transmission line to the outside, so that the data transmission characteristics deteriorate and problems such as interference occur.

  Recently, a balanced transmission system has been proposed in which data transmission is performed by superimposing a high-frequency signal on a power line carrying power such as a commercial power source. In particular, since such a power line is not originally a communication line, the degree of balance may vary depending on the wiring situation in each house, equipment connected to the power source, and the like. For this reason, when a power line is used as a transmission line, the degree of balance may vary depending on each environment, and transmission characteristics may vary greatly.

  Patent Document 1 describes a balanced transmission device that detects an unbalanced component from the voltage or current of a transmission-side or receiving-side conductor and performs transmission control so that the detected unbalanced component is reduced.

  However, Patent Document 1 does not describe a specific method for detecting an unbalanced component.

JP 2004-140565 A

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a line state detection device that can easily and accurately detect the balanced state of a transmission line in a balanced transmission system.

  Another object of the present invention is to provide a communication device and a communication method for a balanced transmission system that can control the balanced state of the transmission line based on the detection result and can improve the degree of balance.

  The line state detection device of the present invention is a line state detection device that detects a state of a transmission line in a balanced transmission system that performs data transmission using a pair of conductors, and detects an unbalanced component between the pair of conductors. An unbalanced component detection unit is provided, and the unbalanced component detection unit detects the unbalanced component based on the state of the pair of conductors during transmission of a pilot signal for detecting the unbalanced component.

  According to the present invention, a pilot signal transmitted through a transmission line can be used with a known characteristic (level, quality, etc.), so that the balanced state of the transmission line in a balanced transmission system can be detected easily and accurately. be able to.

  In the line state detection device of the present invention, the unbalanced component detection unit directly detects the unbalanced component between the pair of conductors.

  In the line state detection device of the present invention, the unbalanced component detection unit detects the current flowing through the conductor and / or the voltage of the conductor for each conductor, and the difference in current for each conductor or for each conductor And calculating the unbalanced component by calculating the difference in voltage or both.

  In the line state detection device of the present invention, the pair of conductors includes a power line.

  In the line state detection apparatus according to the present invention, the pilot signal may include a single carrier signal having a known signal level.

  In the line state detection apparatus according to the present invention, the pilot signal may be a single carrier signal having a known signal level and sweeping over a communication frequency band. According to the present invention, it is possible to reliably detect the equilibrium state of the entire communication band.

  The line state detection apparatus of the present invention includes one in which the pilot signal is a signal having a different frequency for each transmission frame. According to the present invention, the balanced state of the transmission line can be detected without increasing the influence on communication, and the data transfer rate can be increased. Here, the pilot signal for detecting the unbalanced component is not limited to a single carrier signal.

  In the line state detection device of the present invention, the pilot signal includes all carrier signals used in a communication frequency band and carrier signals having known signal levels. According to the present invention, an equilibrium state in a necessary frequency band can be detected simultaneously in a short time.

  The line state detection apparatus of the present invention includes one in which adjacent carrier signals among the plurality of carrier signals are signals orthogonal to each other. According to the present invention, the plurality of carrier signals do not interfere with each other, and the amplitude of the pilot signal does not increase. Therefore, the balanced state of the transmission line can be detected without greatly affecting the data transmission.

  In the line state detection device according to the present invention, the pilot signal is a plurality of discretely selected carrier signals out of all carrier signals used in a communication frequency band, and is a carrier signal having a known signal level. Including. According to the present invention, the equilibrium state of the entire communication band can be detected in a short time with a small number of carriers. Moreover, since the frequency with known disturbance can be avoided, the detection accuracy of the equilibrium state can be improved.

  The line state detection apparatus according to the present invention includes an apparatus including a calculation unit that calculates the unbalanced component of a communication band other than the frequency of the pilot signal based on an output of the unbalanced component detection unit.

  In the line state detection apparatus of the present invention, the calculation unit adds the unbalanced component of the communication band other than the frequency of the pilot signal to the output of the adjacent frequency band of the outputs of the unbalanced component detection unit. Includes those calculated by averaging.

  In the line state detection device of the present invention, the calculating unit calculates the unbalanced component of the communication band other than the frequency of the pilot signal, and the weighted average of the outputs of the adjacent frequency bands among the outputs of the unbalanced component detecting unit. Including those calculated by

  In the line state detection apparatus according to the present invention, the calculation unit obtains the unbalanced component in the band outside the frequency band output from the unbalanced component detection unit from the pilot signal in the nearest frequency band. Includes substitutes for equilibrium components.

  In the line state detection apparatus according to the present invention, the pilot signal is a multi-carrier signal used in a communication frequency band and the first carrier signal having a known signal level is transmitted as the first pilot signal, and then further transmitted. The signal level to be transmitted is a single carrier signal of a known specific frequency. ADVANTAGE OF THE INVENTION According to this invention, while detecting the equilibrium state of the whole communication band for a short time, the state of a specific frequency band can be detected accurately.

  The line state detection apparatus according to the present invention includes one in which the single carrier signal of the specific frequency is a carrier signal in a frequency band having a large unbalance component detected using the first carrier signal. According to the present invention, it is possible to accurately detect an unbalanced component in a short time, and it is possible to monitor a balanced state with high accuracy without increasing the processing load. For example, by detecting a balanced state over the entire communication band, after extracting a frequency band that is highly necessary to monitor the balanced state, a change in the balanced state can be detected only by monitoring the frequency band.

  The line state detection apparatus of the present invention includes one in which the pilot signal is transmitted during a transmission stop period of data to be transmitted. According to the present invention, it is possible to detect an equilibrium state in the same way even during communication or when communication is stopped.

  The line state detection apparatus according to the present invention includes one in which the pilot signal is included in a part or a plurality of parts in a signal train of data to be transmitted. According to the present invention, it is possible to detect an equilibrium state during communication without assigning a special detection time.

  The line state detection apparatus of the present invention includes one in which the pilot signal is transmitted within a certain time from a reference timing signal common to communication systems. According to the present invention, it is possible to easily recognize the processing timing for detecting the equilibrium state.

  In the line state detection device of the present invention, the pilot signal is transmitted in a time division manner at a timing corresponding to each communication device constituting the communication system within a certain time from a reference timing signal common to the communication system. Including some. According to the present invention, the processing timing for detecting the equilibrium state can be easily recognized for each communication device.

  In the line state detection device of the present invention, the pilot signal is assigned to each communication device constituting the communication system, and the assigned pilot signals are transmitted in different bands within the communication frequency band. Including those that are According to the present invention, pilot signals can be detected simultaneously by a plurality of terminals.

  In the line state detection apparatus according to the present invention, the pilot signal may be an AGC reference signal transmitted for AGC (Auto Gain Control) on the receiving side. According to the present invention, since an AGC reference signal, which is a reference signal inserted to determine the operating point of AGC, is used as a pilot signal for detecting the unbalanced component, a detection signal is generated. This means becomes unnecessary. In addition, time for pilot signal transmission becomes unnecessary, and the data transmission rate is improved.

  In the line state detection device according to the present invention, the pilot signal may include a characteristic estimation reference signal for estimating a transmission characteristic of the transmission line. According to the present invention, a characteristic estimation reference signal, which is a reference signal for estimating a transmission band of a transmission line and determining a usable band suitable for communication, is used as a pilot signal for detecting the unbalanced component. This eliminates the need for a means for creating a detection signal. In addition, time for pilot signal transmission becomes unnecessary, and the data transmission rate is improved.

  The line state detection apparatus of the present invention includes one in which the pilot signal is a demodulation reference signal for demodulation on the reception side. According to the present invention, since the demodulation reference signal, which is a reference signal inserted for demodulation synchronization, is used as a pilot signal for detecting the unbalanced component, means for creating a detection signal is provided. It becomes unnecessary. In addition, time for pilot signal transmission becomes unnecessary, and the data transmission rate is improved.

  In the line state detection apparatus according to the present invention, the pilot signal may include a header signal indicating the head of a communication signal. According to the present invention, since the header signal inserted to indicate the head of the communication signal is used as a pilot signal for detecting the unbalanced component, means for creating a detection signal is unnecessary. Become. In addition, time for pilot signal transmission becomes unnecessary, and the data transmission rate is improved.

  The line state detection apparatus of the present invention includes one in which the pilot signal is transmitted at or near a zero cross point of a commercial power source. According to the present invention, when a power line is used as a transmission line, it is possible to reliably detect the influence of a device with a rectifier connected to the power line, particularly a device with a half-wave rectifier.

  In the line state detection apparatus of the present invention, the pilot signal is transmitted at a phase at or near 90 degrees from a zero cross point of a commercial power source or at a phase at or near the phase at −90 degrees from the zero cross point. including.

  The line state detection apparatus of the present invention includes one in which the pilot signal is transmitted within a certain period from a zero cross point of a commercial power source. According to the present invention, pilot signals for a plurality of communication devices can be transmitted without using a reference timing signal.

  The communication device of the present invention is a communication device used in a balanced transmission system that performs data transmission using a pair of conductors, and includes a transmission unit that transmits a transmission signal including the pilot signal described above, and the line state detection device described above. A transmission line state detection device, wherein the unbalanced component detection unit in the transmission line state detection device is based on the state of the pair of conductors during transmission of the pilot signal transmitted from the transmission unit. The component is detected.

  The communication device of the present invention includes a communication device including a transmission signal control unit that controls a transmission signal output to the conductor based on an output of the transmission-side line state detection device.

  The communication apparatus of the present invention includes a communication device in which the transmission signal control unit performs control to reduce an unbalanced component of the transmission line.

  The communication apparatus of the present invention includes a communication device in which the transmission signal control unit controls transmission power of the transmission signal.

  The communication apparatus according to the present invention includes a device in which the transmission signal control unit selects a carrier to be used for communication.

  The communication device of the present invention is a communication device used in a balanced transmission system that performs data transmission using a pair of conductors, and includes a reception-time line state detection device including the above-described line state detection device, and the reception-time line state The unbalanced component detection unit in the detection device includes a unit that detects the unbalanced component based on a state of the pair of conductors during transmission of the pilot signal transmitted from another communication device.

  The communication device of the present invention includes a communication device including a transmission signal control unit that controls a transmission signal output to the conductor based on the output of the reception line state detection device.

  The communication apparatus of the present invention includes a communication device in which the transmission signal control unit performs control to reduce an unbalanced component of the transmission line.

  The communication apparatus of the present invention includes a communication device in which the transmission signal control unit controls transmission power of the transmission signal.

  The communication apparatus according to the present invention includes a device in which the transmission signal control unit selects a carrier to be used for communication.

  The transmission system of the present invention is a balanced transmission system that performs data transmission using a pair of conductors, and includes a communication device that includes the transmission-time line state detection device described above.

  The transmission system of the present invention further includes a communication device including the above-described reception-time line state detection device.

  The communication method of the present invention is a communication method for performing data transmission using a pair of conductors, the step of transmitting a pilot signal for detecting an unbalanced component between the pair of conductors, and the transmission of the pilot signal Detecting the unbalanced component based on the state of the pair of conductors at the time.

  As is apparent from the above description, according to the present invention, it is possible to provide a line state detection device that can easily and accurately detect the balanced state of a transmission line in a balanced transmission system. Further, it is possible to provide a communication device and a balanced transmission system that can control the balanced state of the transmission line based on the detection result and improve the degree of balance.

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

(First embodiment)
FIG. 1 shows a schematic configuration of an example of a balanced transmission system for explaining the first embodiment of the present invention. The balanced transmission system in FIG. 1 performs communication between a first communication device 100 and a second communication device 200 via a transmission line 300 made of a pair of conductors such as power lines.

  The first communication device 100 includes a transmission signal generation unit 11, a transmission control unit 12 (transmission unit), an unbalanced component detection unit 13, and a pilot signal generation unit 14, and the second communication device 200 includes a transmission signal generation. Unit 21, transmission control unit 22, and unbalanced component detection unit 23. In FIG. 1, only elements related to signal transmission are shown, and other elements such as elements related to signal reception are omitted. In addition, although only two communication devices, the first communication device 100 and the second communication device 200, are connected to the transmission line 300, another communication device may be connected. The plurality of communication devices connected to the transmission line 300 may be the first communication device 100 or the second communication device 200, but at least one communication device is the first communication device 100. .

  The transmission signal generation unit 11 generates a transmission signal to be transmitted via the transmission line 300 and a transmission signal (multicarrier transmission signal) for performing transmission using a plurality of subcarriers. The transmission method using a plurality of subcarriers is, for example, an OFDM (Orthogonal Frequency Division Multiplexing) method using wavelet transform. The transmission signal generation unit 11 transmits the pilot signal generated by the pilot signal generation unit 14 together. Information such as the transmission timing of the pilot signal is sent to the unbalanced component detector 13. The pilot signal is a signal transmitted to detect an unbalanced component of the transmission line, and details will be described later.

  The transmission control unit 12 controls the transmission signal generated by the transmission signal generation unit 11 according to the state of the transmission line. For example, the transmission control unit 12 performs transmission signal balance control and transmission power control. These controls are controls for reducing the unbalanced component of the transmission line 300 detected by the unbalanced component detector 13 (unbalanced component between a pair of conductors constituting the transmission line 300).

  When performing balance control of a transmission signal, for example, a compensation signal calculated based on an unbalanced component is added to each of a pair of transmission signals. FIG. 2 is a conceptual diagram of an example of balance control. In FIG. 2, the transmission signals e and -e from the transmission signal generator 11 are added to the compensation signal ec and transmitted to the conductors 31 and 32, respectively. When performing transmission power control of a transmission signal, for example, the amplification degree of an amplifier (not shown) connected to each of the pair of conductors 31 and 32 of the transmission line 300 is controlled.

  In the example of FIG. 1, the unbalanced component is reduced mainly by analog processing under the control of the transmission control unit 12, but information on the unbalanced component is sent to the transmission signal generating unit 11 and the unbalanced component is digitally processed. It is also possible to generate a transmission signal with a reduced value. Alternatively, the unbalanced component of the transmission line 300 may be reduced by not using subcarriers in a frequency band having a large unbalanced component.

  The unbalanced component detector 13 detects an unbalanced component between a pair of conductors constituting the transmission line 300, and detects an unbalanced component during transmission of the pilot signal. FIG. 3 shows a schematic configuration of an example of the unbalanced component detection unit 13. 3 directly detects an unbalanced component between a pair of conductors, and a current transformer 41 is connected to the conductors 31 and 32 in series. When the secondary winding of the current transformer 41 is connected so as to detect the current in the same direction of the conductors 31 and 32 as shown in FIG. 3, the secondary winding current indicates an unbalanced component between the conductors 31 and 32. It will be. The unbalanced component detector 13 outputs an unbalanced component signal between the conductors 31 and 32 based on the secondary winding current.

  FIG. 4 shows a schematic configuration of another example of the unbalanced component detection unit 13. The one shown in FIG. 4 is to indirectly detect an unbalanced component between a pair of conductors. By separately detecting the currents flowing through the conductors 31 and 32 constituting the transmission line, and obtaining the difference between them, Calculate the unbalanced component. The current flowing through the conductors 31 and 32 is obtained by detecting the voltage across the impedances 51a and 51b connected in series to the conductors 31 and 32 with the voltage detectors 52a and 52b. The unbalanced component detector 13 outputs an unbalanced component signal between the conductors 31 and 32 based on the voltage values of the voltage detectors 52a and 52b. In the example of FIG. 4, the unbalanced component is calculated by obtaining the difference between the currents flowing through the conductors 31 and 32. However, the voltage is calculated by separately detecting the voltage of the conductors 31 and 32. It is also possible to do. Further, both the current difference and the voltage difference may be used.

  The pilot signal generation unit 14 generates a pilot signal transmitted to the transmission line 300 in order to detect an unbalanced component of the transmission line 300. Since the unbalanced component of the transmission line 300 is to detect the unbalanced component during transmission of the signal to the transmission line 300, it is preferable that the signal being transmitted is known and of good quality. Specifically, it is preferable that the frequency band covers the entire band used, the signal features (level, quality, etc.) are known, and normal communication operation is not hindered by transmitting a pilot signal. In addition, it is not necessary to add a special circuit to the generation of the pilot signal, the unbalanced component can be detected with a short time transmission, can be transmitted with an appropriate period, and can be changed according to the change of the situation. It is preferable. A specific example of the pilot signal will be described later.

  The first communication device 100 having the above configuration transmits the pilot signal generated by the pilot signal generation unit 14 at a predetermined timing, and detects the unbalanced component of the transmission line 300 during the pilot signal transmission. Based on the detected unbalanced component, the transmission control unit 12 controls the transmission signal so that the unbalanced component is reduced.

  The transmission signal generation unit 21, the transmission control unit 22, and the unbalanced component detection unit 23 of the second communication device 200 are the transmission signal generation unit 11, the transmission control unit 12, and the unbalanced component detection unit 13 of the first communication device 100. Detailed description will be omitted. However, the unbalanced component detector 23 detects the unbalanced component of the transmission line 300 that is receiving the pilot signal. The transmission control unit 22 controls the transmission signal from the transmission signal generation unit 21 based on the detected unbalanced component.

  Next, the type of pilot signal generated by the pilot signal generation unit 14 and the signal timing of the pilot signal will be described.

(Single carrier signal)
An example of the operation when a single carrier signal is used as a pilot signal will be described with reference to FIG. FIG. 5A shows the relationship between the pilot signal and the communication band, and FIGS. 5B and 5C show the transmission timing of the pilot signal.

  As shown in FIG. 5A, the pilot signal 501 is a carrier signal having an arbitrary frequency within the communication band, and its signal level is known. The pilot signal 501 may be transmitted prior to transmission data including a header signal indicating the start of a transmission signal (hereinafter simply referred to as a header signal), a data signal, and an end signal indicating the end of the transmission signal (hereinafter simply referred to as an end signal). It may be transmitted between the header signal and the data signal (see FIG. 5C). In this case, the unbalanced component detectors 13 and 23 detect an unbalanced component in a specific frequency band of the transmission line 300, and the transmission control units 12 and 22 are controlled by the unbalanced component signal.

  Another example of the operation when a single carrier signal is used as a pilot signal will be described with reference to FIG. FIG. 6A shows the relationship between the pilot signal and the communication band, and FIG. 6B shows the transmission timing of the pilot signal. Pilot signal 601 in FIG. 6 is a single carrier signal swept over the communication frequency band. When this pilot signal 601 is transmitted, an unbalanced component in the entire communication band can be reliably detected.

  Still another example of the operation when a single carrier signal is used as a pilot signal will be described using the transmission timing of the pilot signal shown in FIG. Pilot signals 701 and 702 in FIG. 7 are carrier signals having different frequencies, and are transmitted by changing every transmission frame. In the example of FIG. 7, the pilot signal 701 is transmitted in the nth signal sequence, and the pilot signal 702 is transmitted in the n + 1th signal sequence. When such a pilot signal is transmitted, an unbalanced component of the entire communication band can be detected after a certain frame transmission. In addition, the balanced state of the transmission line can be detected without increasing the influence on communication, and the data transfer rate can be increased.

  In the example of FIG. 7, the pilot signal to be transmitted is described as a single carrier signal, but there is no problem with a multicarrier signal. In that case, by selecting the carrier to be used for each frame, the unbalanced component of the entire communication band can be detected in a short time.

(Multi-carrier signal)
An example of the operation when using a plurality of carrier signals as pilot signals will be described with reference to FIG. FIG. 8A shows the relationship between the pilot signal and the communication band, and FIG. 8B shows the transmission timing of the pilot signal.

  As shown in FIG. 8A, the pilot signal 801 is a carrier signal of all frequencies in the communication band, and its signal level is known. The pilot signal 801 is transmitted between the header signal and the data signal in the example of FIG. When such a pilot signal is transmitted, an unbalanced component in a necessary frequency band can be simultaneously detected in a short time. Also, carrier signals adjacent to each other among a plurality of carrier signals do not interfere with each other and do not increase the amplitude of the pilot signal by making the carrier signals orthogonal to each other. The equilibrium state of the transmission line can be detected.

  Another example of the operation when using a plurality of carrier signals as pilot signals will be described with reference to FIG. FIG. 9A shows the relationship between pilot signals and communication bands, and FIG. 9B shows pilot signal transmission timing.

  As shown in FIG. 9A, the pilot signal 901 is a plurality of discretely selected carrier signals among all the carrier signals used in the communication band (the broken line in FIG. 9A indicates communication). This is a carrier to be used but not included in the pilot signal.) In the example of FIG. 9B, the pilot signal 901 is transmitted between the header signal and the data signal.

  By transmitting such a pilot signal 901, it is possible to detect in a short time an unbalanced component over the entire communication band, although it is discrete with a small number of carriers. Further, since a frequency with a known disturbance (number 902 in FIG. 9A) can be avoided, the detection accuracy of the equilibrium state can be improved.

  When detecting an unbalanced component in a region corresponding to all carriers in the entire communication band, the calculation is performed by performing a predetermined calculation based on the unbalanced component in the region included in the pilot signal. The calculation unit that performs this calculation may be the unbalanced component detection units 13 and 23, or a calculation unit (not shown) may be provided outside the unbalanced component detection units 13 and 23. As such a calculation, for example, an arithmetic average or a weighted average of unbalanced component outputs in adjacent frequency bands can be employed. Further, the unbalanced component in the band outside the frequency band output by the unbalanced component detectors 13 and 23 is replaced with the unbalanced component in the nearest frequency band.

(Single carrier signal and multi-carrier signal)
An example of the operation when a single carrier signal is used as a pilot signal after using a plurality of carrier signals as a pilot signal will be described with reference to FIG. FIG. 10A shows the relationship between the first pilot signal 1001 that is a plurality of carrier signals and the communication band, and FIG. 10B shows the second pilot signal 1002 that is a single carrier signal and the communication band. The relationship is shown.

  The first carrier signal 1001 is a carrier signal of all frequencies in the communication band, like the pilot signal 801 shown in FIG. 8A, and its signal level is known. The second carrier signal 1002 is a single carrier signal having a specific frequency, similar to the pilot signal 501 shown in FIG. The second carrier signal 1002 is used to detect the balanced state of the transmission line at a specific frequency. For example, the second carrier signal 1002 can be used to grasp detailed data of unbalanced components, This is used for the purpose of detecting an equilibrium component.

  In this example, after the first pilot signal 1001 is transmitted for a short time to detect the unbalanced component of the entire communication band at the same time, the second pilot signal 1002 is transmitted to increase the unbalanced component in the selected frequency band. Detect with accuracy.

  Another example of the operation when a single carrier signal is used as a pilot signal after using a plurality of carrier signals as a pilot signal will be described with reference to FIG. FIG. 11A shows the relationship between the first pilot signal 1101 that is a plurality of carrier signals and the communication band, and FIG. 11C shows the second pilot signal 1102 that is a single carrier signal and the communication band. The relationship is shown. FIG. 11B shows an unbalanced component 1103 detected by transmitting the first pilot signal 1101.

  The first carrier signal 1101 is a carrier signal of all frequencies in the communication band, like the pilot signal 801 shown in FIG. 8A, and its signal level is known. The second carrier signal 1102 is a single carrier signal having a specific frequency, similar to the pilot signal 501 shown in FIG. The second carrier signal 1102 is a single carrier signal having a frequency selected based on the magnitude of the unbalanced component shown in FIG.

  In this example, after the first pilot signal 1101 is transmitted for a short time to detect the unbalanced component of the entire communication band at the same time, the frequency band having a large unbalanced component (that is, the band including the peak of the unbalanced component 1103) is Two pilot signals 1102 are transmitted to detect an unbalanced component in a region where the balanced state is not good with high accuracy. The unbalanced component can be detected accurately in a short time, and the balanced state can be monitored with high accuracy without increasing the processing load.

(Pilot signal transmission timing)
Pilot signal transmission timing will be described with reference to FIGS.

  FIG. 12 is a diagram illustrating transmission timing when data is transmitted during a transmission stop period of data to be transmitted. As shown in FIG. 12, the pilot signal 1201 is transmitted between the nth signal sequence and the (n + 1) th signal sequence, and the pilot signal 1202 is transmitted between the (n + 1) th signal sequence and an n + 2th signal sequence (not shown). Sent to. If transmission is performed at this timing, the balanced state can be detected by the same method during communication or when communication is stopped.

  FIG. 13 is a diagram showing the transmission timing in the case of being transmitted by being included in the signal train of data to be transmitted. As shown in FIG. 13, pilot signal 1301 is transmitted between the header signal and the data signal. If transmission is performed at this timing, it is possible to detect an equilibrium state during communication without assigning a special detection time. In the example of FIG. 13, the pilot signal is inserted at one place in one signal sequence, but it may be inserted at a plurality of places.

  FIG. 14 and FIG. 15 are diagrams illustrating transmission timings when transmission is performed at a timing based on a reference timing signal common to communication systems (hereinafter referred to as a beacon signal).

  FIG. 14 shows a case where the pilot signal 1401 is transmitted after a certain time t from the transmission of the beacon signal. When the pilot signal is transmitted at this timing, the unbalanced component detectors 13 and 23 can easily recognize the processing timing for detecting the balanced state. 14 is the time from the leading edge of the beacon signal, it may be the time from the trailing edge.

  FIG. 15 shows a case where pilot signals 1501 to 150n corresponding to each communication device are transmitted in a time division manner after a certain time t from the transmission of the beacon signal. When the pilot signal is transmitted at this timing, the unbalanced component detectors 13 and 23 for each communication device can easily recognize the processing timing for detecting the balanced state. The fixed time t in FIG. 15 is the time from the leading edge of the beacon signal, but may be the time from the trailing edge.

  FIG. 16 is a diagram for explaining an operation in the case of transmitting pilot signals assigned to a plurality of communication apparatuses constituting the communication system. FIG. 16A shows a communication band, and FIG. 16B shows different frequency bands of pilot signals 1601 and 1602. That is, pilot signal 1601 is a carrier signal in region A, and pilot signal 1602 is a carrier signal in region B. FIGS. 16C and 16D show pilot signal detection timings in different communication apparatuses. In this case, a pilot signal is assigned to each communication device constituting the communication system, and each assigned pilot signal is transmitted in a different band within the communication frequency band. If the pilot signal is transmitted at this timing, the pilot signal can be detected simultaneously by a plurality of terminals. It is also possible to transmit each pilot signal by time division.

  The pilot signal transmission timing when applied to power line communication and the like will be described with reference to FIGS.

  FIG. 17 shows the transmission timing when the pilot signal is transmitted in the vicinity of the zero cross point of the commercial power supply. As shown in FIG. 17, pilot signal 1701 is transmitted in the vicinity of zero cross point 1702 of the commercial power source. The commercial power supply is easily affected by peripheral devices, especially devices with a half-wave rectifier, during period 1703, so transmission near the zero cross point 1702 ensures that unbalanced components are detected without being affected by the peripheral devices. can do. It is also possible to transmit the pilot signal at the zero cross point.

  FIG. 18 shows the transmission timing when the pilot signal is transmitted in the vicinity of 90 degrees from the zero cross point of the commercial power supply. As shown in FIG. 18, pilot signal 1801 is transmitted at a phase of 90 degrees from the zero cross point 1802 of the commercial power supply. Since the period 1803 is easily affected by peripheral devices, particularly devices with a half-wave rectifier, the influence of the peripheral devices can be reliably detected. In FIG. 18, transmission is performed at a phase that is 90 degrees from the zero cross point 1802 of the commercial power supply. However, the effect is the same if transmission is performed at a phase that is −90 degrees from the zero cross point.

  FIG. 19 shows the transmission timing when the pilot signal is transmitted within a certain period with the zero cross point of the commercial power supply as a reference. 19 shows an example in which a plurality of pilot signals 1901, 1902,... 190n corresponding to a plurality of communication apparatuses are transmitted. If a pilot signal is transmitted at such timing, it can be transmitted at accurate timing without using a beacon signal.

(Second Embodiment)
FIG. 20 shows a schematic configuration of an example of a balanced transmission system for explaining the second embodiment of the present invention. The difference from the first embodiment is that the pilot signal generator 14 is omitted. As the pilot signal, a communication control signal included in the data transmission sequence is used. Specifically, an AGC reference signal (for example, a reference signal for controlling the gain of the receiving circuit) transmitted for AGC (Auto Gain Control) on the receiving side, and characteristic estimation for estimating transmission characteristics of the transmission line A reference signal for demodulation, a reference signal for demodulation for demodulation on the receiving side (for example, a reference signal of phase and amplitude), a header signal indicating the head of the communication signal, and the like are used.

  The second communication device 200 shown in FIG. 20 further includes a reception unit 24 including a signal amplification circuit 241, an AGC circuit 242, and a demodulation circuit 243, and a data processing unit 25, and performs AGC control, transmission characteristic estimation, and the like. Since the AGC control and transmission characteristic estimation processing of the signal amplifier circuit are well known, description thereof will be omitted.

  The pilot signal transmission timing in the balanced transmission system for describing the second embodiment will be described with reference to FIGS.

  FIG. 21 shows a case where the AGC reference signal 2101 is used. As shown in FIG. 21, the AGC reference signal 2101 is transmitted prior to the data signal.

  FIG. 22 shows a case where the characteristic estimation reference signal 2201 for estimating the transmission characteristic of the transmission line is used. As shown in FIG. 22, the characteristic estimation reference signal 2201 is transmitted between the header signal and the data signal.

  FIG. 23 shows a case where a demodulation reference signal 2301 for demodulation on the receiving side is used. As shown in FIG. 23, the demodulation reference signal 2301 is transmitted between the header signal and the data signal.

  FIG. 24 shows a case where a header signal 2401 indicating the head of a communication signal is used. As shown in FIG. 24, the header signal 2401 is transmitted at the head of the communication signal.

  INDUSTRIAL APPLICABILITY The present invention is useful as a line state detection device that can easily and accurately detect the balanced state of a transmission line in a balanced transmission system in a balanced transmission system that performs data transmission using a pair of conductors. Further, the balanced state of the transmission line can be controlled based on the detection result, and it is useful as a communication device, a communication method, and the like of the balanced transmission system that can improve the balance.

The figure which shows schematic structure of an example of the balanced transmission system for demonstrating the 1st Embodiment of this invention. The conceptual diagram of an example of balance degree control in the balanced transmission system for demonstrating the 1st Embodiment of this invention The figure which shows schematic structure of an example of the unbalanced component detection part in the balanced transmission system for demonstrating the 1st Embodiment of this invention. The figure which shows schematic structure of the other example of the unbalanced component detection part in the balanced transmission system for demonstrating the 1st Embodiment of this invention. The figure explaining an example of operation | movement in the case of using a single carrier signal as a pilot signal in the balanced transmission system for demonstrating the 1st Embodiment of this invention. The figure explaining the other example of operation | movement when using a single carrier signal as a pilot signal in the balanced transmission system for describing the 1st Embodiment of this invention. The figure explaining another example of operation | movement in the case of using a single carrier signal as a pilot signal in the balanced transmission system for describing the 1st Embodiment of this invention. The figure explaining an example of operation | movement in case the some carrier signal is utilized as a pilot signal in the balanced transmission system for demonstrating the 1st Embodiment of this invention. The figure explaining the other example of operation | movement in case the some carrier signal is utilized as a pilot signal in the balanced transmission system for demonstrating the 1st Embodiment of this invention. The figure explaining an example of operation | movement in the case of using a single carrier signal as a pilot signal, after using a several carrier signal as a pilot signal in the balanced transmission system for describing the 1st Embodiment of this invention. Another example of operation when a single carrier signal is used as a pilot signal after using a plurality of carrier signals as a pilot signal in the balanced transmission system for explaining the first embodiment of the present invention will be described. Figure to The figure which shows the transmission timing in the case of transmitting a pilot signal in the transmission stop period of the data which should be transmitted in the balanced transmission system for demonstrating the 1st Embodiment of this invention. The figure which shows the transmission timing in the case of transmitting a pilot signal included in the signal sequence of the data which should be transmitted in the balanced transmission system for demonstrating the 1st Embodiment of this invention. The figure which shows the transmission timing in the case of transmitting a pilot signal after a fixed time from beacon signal transmission in the balanced transmission system for demonstrating the 1st Embodiment of this invention. The figure which shows the transmission timing in the balanced transmission system for demonstrating the 1st Embodiment of this invention when the pilot signal corresponding to each communication apparatus is transmitted by a time division after the fixed time from beacon signal transmission. The figure for demonstrating the operation | movement in the case of transmitting the pilot signal allocated for every some communication apparatus which comprises a communication system in the balanced transmission system for describing the 1st Embodiment of this invention. The figure which shows the transmission timing in the case of transmitting a pilot signal in the vicinity of the zero crossing point of a commercial power supply in the balanced transmission system for describing the first embodiment of the present invention. The figure which shows the transmission timing in the case of transmitting a pilot signal in the vicinity of 90 degree | times from the zero cross point of a commercial power source in the balanced transmission system for demonstrating the 1st Embodiment of this invention. The figure which shows the transmission timing in the balanced transmission system for demonstrating the 1st Embodiment of this invention in case a pilot signal is transmitted within a fixed period on the basis of the zero crossing point of a commercial power source. Conceptual diagram of an example of balance degree control in a balanced transmission system for explaining a second embodiment of the present invention The figure explaining the transmission timing of the pilot signal in the balanced transmission system for demonstrating 2nd Embodiment The figure explaining the transmission timing of the pilot signal in the balanced transmission system for demonstrating 2nd Embodiment The figure explaining the transmission timing of the pilot signal in the balanced transmission system for demonstrating 2nd Embodiment The figure explaining the transmission timing of the pilot signal in the balanced transmission system for demonstrating 2nd Embodiment The figure which shows an example of the transmission part and transmission line of the conventional balanced transmission apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... 1st communication apparatus 200 ... 2nd communication apparatus 300 ... Transmission line 11, 21 ... Transmission signal generation part 12, 22 ... Transmission control part 13, 23 ... Unbalanced component Detection unit 14 ... Pilot signal generation unit 24 ... Reception unit 25 ... Data processing unit 241 ... Signal amplification circuit 242 ... AGC circuit 243 ... Demodulation circuit 31, 32 ... Conductor 41 ... Current transformers 51a, 51b ... Impedances 52a, 52b ... Voltage detectors

Claims (41)

A line state detection device for detecting a state of a transmission line in a balanced transmission system that performs data transmission using a pair of conductors,
An unbalanced component detection unit for detecting an unbalanced component between the pair of conductors;
The unbalanced component detection unit is a line state detection device that detects the unbalanced component based on the state of the pair of conductors during transmission of a pilot signal for detecting the unbalanced component. The line state detection device according to claim 1,
The unbalanced component detection unit is a line state detection device that directly detects an unbalanced component between the pair of conductors. The line state detection device according to claim 1,
The unbalanced component detection unit detects a current flowing in the conductor and / or a voltage of the conductor for each conductor, and obtains a difference in current for each conductor and / or a difference in voltage for each conductor. A line state detection device for calculating the unbalanced component. The line state detection device according to any one of claims 1 to 3,
The pair of conductors is a line state detection device which is a power line. The line state detection device according to any one of claims 1 to 4,
The pilot signal is a line state detection device in which a signal level is a known single carrier signal. The line state detection device according to any one of claims 1 to 4,
The pilot signal is a line state detection device which is a single carrier signal having a known signal level and sweeping over a communication frequency band. The line state detection device according to any one of claims 1 to 4,
The pilot signal is a line state detection device that is a signal having a different frequency for each transmission frame. The line state detection device according to any one of claims 1 to 4,
The pilot signal is a line state detection device in which all the carrier signals used in the communication frequency band are carrier signals with known signal levels. The line state detection device according to claim 8,
The line state detection device in which adjacent carrier signals among the plurality of carrier signals are signals orthogonal to each other. The line state detection device according to any one of claims 1 to 4,
The pilot signal is a line state detection device in which a plurality of discretely selected carrier signals among all carrier signals used in a communication frequency band are carrier signals with known signal levels. The line state detection device according to claim 10,
A line state detection apparatus comprising: a calculating unit that calculates the unbalanced component of a communication band other than the frequency of the pilot signal based on an output of the unbalanced component detecting unit. The line state detection device according to claim 11,
The line state detection device, wherein the calculation unit calculates the unbalanced component of a communication band other than the frequency of the pilot signal by an arithmetic average of outputs of adjacent frequency bands among outputs of the unbalanced component detection unit. The line state detection device according to claim 11,
The line state detection device, wherein the calculation unit calculates the unbalanced component of a communication band other than the frequency of the pilot signal by weighted average of outputs of adjacent frequency bands among outputs of the unbalanced component detection unit. The line state detection device according to claim 11,
The calculation unit substitutes the unbalanced component obtained from the pilot signal in the nearest frequency band for the unbalanced component in the band outside the frequency band output by the unbalanced component detection unit. . The line state detection device according to any one of claims 1 to 4,
The pilot signal is a first carrier signal having a known signal level, which is a multi-carrier signal used in a communication frequency band, and a specific frequency whose signal level is further transmitted after being transmitted as the first pilot signal. Line state detection device which is a single carrier signal. The line state detection device according to claim 15,
The line state detection device, wherein the single carrier signal of the specific frequency is a carrier signal in a frequency band having a large unbalance component detected using the first carrier signal. The line state detection device according to any one of claims 1 to 16,
The pilot signal is a line state detection device that is transmitted during a transmission stop period of data to be transmitted. The line state detection device according to any one of claims 1 to 16,
The line state detection device, wherein the pilot signal is included in a part or a plurality of parts in a signal train of data to be transmitted. The line state detection device according to any one of claims 1 to 16,
The pilot signal is a line state detection device which is transmitted within a certain time from a reference timing signal common to communication systems. The line state detection device according to claim 19,
The pilot signal is a line state detection device which is transmitted in a time division manner at a timing corresponding to each communication device constituting the communication system within a certain time from a reference timing signal common to the communication system. The line state detection device according to any one of claims 1 to 16,
The pilot signal is assigned to each communication device constituting the communication system, and the assigned pilot signals are transmitted in different bands within the communication frequency band. The line state detection device according to any one of claims 1 to 4,
The pilot signal is a line state detection device which is an AGC reference signal transmitted for AGC on the receiving side. The line state detection device according to any one of claims 1 to 4,
The pilot signal is a line state detection device which is a characteristic estimation reference signal for estimating transmission characteristics of a transmission line. The line state detection device according to any one of claims 1 to 4,
The pilot signal is a line state detection device which is a demodulation reference signal for demodulation on the receiving side. The line state detection device according to any one of claims 1 to 4,
The pilot signal is a line state detection device which is a header signal indicating the head of a communication signal. The line state detection device according to any one of claims 1 to 25,
The pilot signal is a line state detection device that is transmitted at or near a zero cross point of a commercial power source. The line state detection device according to any one of claims 1 to 25,
The line state detection device, wherein the pilot signal is transmitted at or near a phase that is 90 degrees from a zero cross point of a commercial power source or at a phase that is -90 degrees from or near the zero cross point. The line state detection device according to any one of claims 1 to 25,
The pilot signal is a line state detection device that is transmitted within a certain period from a zero cross point of a commercial power source. A communication device used in a balanced transmission system that performs data transmission using a pair of conductors,
A transmitter for transmitting a transmission signal including the pilot signal according to any one of claims 1 to 28;
A transmission line state detection device comprising the line state detection device according to any one of claims 1 to 28,
The unbalanced component detection unit in the transmission line state detection device detects the unbalanced component based on the state of the pair of conductors when the pilot signal transmitted from the transmission unit is transmitted. 30. The communication device according to claim 29, wherein
A communication apparatus provided with the transmission signal control part which controls the transmission signal output with respect to the said conductor based on the output of the said transmission side track | line state detection apparatus. The communication device according to claim 30, wherein
The transmission signal control unit is a communication device that performs control to reduce an unbalanced component of the transmission line. The communication device according to claim 30 or 31, wherein
The transmission signal control unit is a communication device that controls transmission power of the transmission signal. A communication device according to any one of claims 30 to 32,
The transmission signal control unit is a communication device that selects a carrier to be used for communication. A communication device used in a balanced transmission system that performs data transmission using a pair of conductors,
A receiving line state detecting device comprising the line state detecting device according to any one of claims 1 to 28,
The communication device that detects the unbalanced component based on the state of the pair of conductors when transmitting the pilot signal transmitted from another communication device. 35. The transmission device according to claim 34, wherein
A communication apparatus provided with the transmission signal control part which controls the transmission signal output with respect to the said conductor based on the output of the said receiving time line state detection apparatus. 36. The communication device according to claim 35, wherein
The transmission signal control unit is a communication device that performs control to reduce an unbalanced component of the transmission line. The communication device according to claim 35 or 36, wherein:
The transmission signal control unit is a communication device that controls transmission power of the transmission signal. A communication device according to any one of claims 35 to 37,
The transmission signal control unit is a communication device that selects a carrier to be used for communication. A balanced transmission system that performs data transmission using a pair of conductors,
A balanced transmission system comprising the communication device according to any one of claims 30 to 33. A balanced transmission system according to claim 39, wherein
A balanced transmission system comprising the communication device according to any one of claims 35 to 38. A communication method for transmitting data using a pair of conductors,
Transmitting a pilot signal for detecting an unbalanced component between the pair of conductors;
A communication method comprising a step of detecting the unbalanced component based on a state of the pair of conductors during transmission of the pilot signal.

Images