JP4563232B2 - Line state detection device, communication device, balanced transmission system, and line state detection method - Google Patents

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 such as a telephone line is often used, and the 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 (not shown) is originally required to be completely balanced, but in actuality, the unbalanced elements in the transmission unit and the reception unit and the transmission line wiring situation In fact, there are unbalanced components due to devices connected in the middle, and 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, part of the transmission power leaks from the transmission line to the outside, data transmission characteristics deteriorate, and problems such as interference may occur. It has been confirmed that such high-frequency unbalanced power, leakage power, and radiation amount are correlated.

  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 cannot be maintained depending on the wiring situation in each house, the 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 the individual environment, which may cause radiation or interference due to leakage current.

  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 a line state detection device that can quickly determine an unbalanced state of a required frequency band of a transmission line in a balanced transmission system with a simple configuration. The purpose is to provide.

  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, and a leakage power determination unit that determines a state of leakage power of the transmission line based on the unbalanced component signal detected by the unbalanced component detection unit, the leakage power determination unit A sine wave signal generator, a frequency mixer for mixing the sine wave signal from the sine wave signal generator and the unbalanced component signal, and a bandpass filter to which the output signal of the frequency mixer is input. Then, the magnitude of the leakage power is determined based on the output of the band pass filter.

  The line state detection method of the present invention is a line state detection method for detecting the 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 step, and a leakage power determination step of determining a state of leakage power of the transmission line based on the unbalanced component signal detected in the unbalanced component detection step, wherein the leakage power determination step A frequency mixing step of mixing the sine wave signal and the unbalanced component signal, and a step of determining the magnitude of the leakage power based on an output obtained by band-passing the output signal of the frequency mixing step.

  ADVANTAGE OF THE INVENTION According to this invention, the state of the leakage power of the required frequency band of the transmission line in a balanced transmission system can be determined rapidly with a simple structure. Further, even in an existing system, the state of leakage power can be performed by adding a simple circuit without major changes.

  The line state detection apparatus according to the present invention includes a device in which the leakage power determination unit determines the magnitude of the leakage power based on the unbalanced component signal when an unmodulated multicarrier signal is transmitted. According to the present invention, the unmodulated multicarrier signal is already used as a signal sequence in the balanced transmission system, and the leakage power of the transmission line can be detected without transmitting a special detection signal.

  The line state detection apparatus of the present invention further includes a determination control unit that controls the leakage power determination unit, and the determination control unit includes the generated sine wave frequency of the sine wave signal generator and the pass frequency of the band pass filter. Including one that controls at least one of the bands. ADVANTAGE OF THE INVENTION According to this invention, the leakage power of the arbitrary frequency bands of a transmission line can be determined rapidly.

  In the line state detection device according to the present invention, the determination control unit may sweep the generated sine wave frequency of the sine wave signal generator. ADVANTAGE OF THE INVENTION According to this invention, the leakage power for every frequency band of a transmission line can be determined rapidly.

  The line state detection device of the present invention further includes a detection frequency setting unit that sets a frequency band in which the leakage power is to be detected, and the determination control unit generates the sine wave signal based on the set frequency band. For controlling at least one of a generator sine wave frequency and a pass frequency band of the band pass filter.

  In the line state detection device of the present invention, the detection frequency setting unit holds priority detection frequency band information corresponding to a country in which the balanced transmission system is to be installed, and priority corresponding to country information instructed from the outside The output includes a frequency band based on the detected frequency band information to the determination control unit.

  In the line state detection device of the present invention, the detection frequency setting unit estimates the length of the transmission line based on the reception intensity at the communication partner, and the priority detection frequency band based on the resonance frequency of the transmission line of the estimated length And outputting the obtained priority detection frequency band to the determination control unit as a frequency band to be detected.

  In the line state detection device of the present invention, the detection frequency setting unit outputs to the determination control unit a frequency band in which leakage power has been large in the past as a frequency band to be detected.

  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.

  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 the above-described line state detection device.

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

  ADVANTAGE OF THE INVENTION According to this invention, the state of the unbalanced power of the required frequency band of the transmission line in a balanced transmission system can be determined quickly with a simple configuration. 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.

  FIG. 1 shows a schematic configuration of a communication apparatus for explaining a first embodiment of the present invention. The communication apparatus in FIG. 1 performs communication via a transmission line composed of a pair of conductors 61 and 62 such as a power line. The communication apparatus of FIG. 1 includes a digital signal processing unit 1, an analog circuit unit 2, a communication transformer 3, an unbalanced component detection unit (broken line frame) 4, and a leakage power determination unit 5.

  The digital signal processing unit 1 is composed of, for example, a digital LSI, modulates digital transmission data to generate a digital transmission signal, demodulates the digital reception signal to generate digital reception data, and signals from each part of the analog circuit unit 2 Control path, gain, etc. The digital transmission signal 1 a is sent to the analog front end chip (AFE chip) 21 of the analog circuit unit 2, and the digital reception signal 1 a is input from the AFE chip 21. Various control signals and status signal 1 b are also input / output from / to the AEF chip 21. The modulation / demodulation processing in the digital signal processing unit 1 uses a plurality of subcarriers, and is, for example, OFDM (Orthogonal Frequency Division Multiplexing) using wavelet transform.

  The digital signal processing unit 1 includes a detection frequency setting unit 11 that sets a frequency band determined by the leakage power determination unit 5 and a determination control unit 12 that controls the determination operation of the leakage power determination unit 5. These elements will be described later.

  The analog circuit unit 2 includes an analog front end (AFE) chip 21, a transmission filter 22, a transmission amplifier 23, a transmission switch 24, a reception filter 25, and a reception AGC (Auto Gain Control) amplifier 26.

  The AFE chip 21 includes a transmission DA converter 21a that converts the digital transmission signal 1a from the digital signal processing unit 1 into an analog transmission signal, and a reception AD converter that converts an analog reception signal from the reception AGC amplifier 26 into a digital reception signal. 21b is included. The transmission filter 22 is a low-pass filter that removes harmonic noise generated by DA conversion in the transmission DA converter 21a. The transmission amplifier 23 amplifies the transmission power of the analog transmission signal, and generates transmission power according to the impedance of a transmission line such as a power line. The transmission switch 24 switches transmission / reception signals, mutes the transmission amplifier 23 during reception, and switches impedance between transmission and reception.

  The reception filter 25 is a band filter that removes noise at a frequency outside the communication band, and the reception AGC amplifier 26 amplifies the analog reception signal. The reception signal AGC amplifier 26 amplifies the analog reception signal to a voltage suitable for the resolution of the reception DA converter 21b. To be adjusted.

  The communication transformer 3 is for transmitting and receiving signals by insulating a communication signal from a primary circuit on the communication device side and a secondary circuit on the transmission line side.

  The unbalanced component detector 4 detects an unbalanced component between the pair of conductors 61 and 62 serving as a transmission line. The unbalanced component detector 4 is a current transformer, for example, and is connected so that the secondary winding current of the current transformer flows as a differential current between the current of the conductor 61 and the current of the conductor 62. In this case, the secondary winding current indicates an unbalanced component corresponding to the leakage power from the transmission lines 61 and 62.

  The unbalanced component detection unit 4 thus obtained the unbalanced components of the transmission lines 61 and 62 by detecting the differential current of each line, but detects the voltage or current and voltage of each line 61 and 62. Can also be obtained. Further, the unbalanced component can be directly obtained from the electromagnetic wave detected by the loop antenna provided in the vicinity of the transmission lines 61 and 62. In that case, the loop antenna may be provided inside the casing (not shown) of the communication apparatus or may be provided separately. In addition, an induction coil can be used instead of the loop antenna.

  The leakage power detection determination unit 5 determines the state of leakage power of the transmission lines 61 and 62 based on the unbalanced component signal detected by the unbalanced component detection unit 4, and includes a first RF (Radio Frequency) filter 51, A frequency mixer 52, a second RF filter (bandpass filter) 53, a peak detection circuit (broken frame) 54, a comparator 55, and a sine wave generation circuit (sine wave signal generator) 56 are configured.

  The first RF filter 51 is a band filter that removes out-of-band noise of the unbalanced component signal from the unbalanced component circuit 4. The frequency mixer 52 multiplies the unbalanced component signal by the sine wave signal from the sine wave generation circuit 56 and performs frequency conversion. The sine wave generation circuit 56 is a circuit that generates a sine wave signal to be frequency mixed, and the generation frequency thereof is variable.

  The second RF filter 53 filters the signal frequency-converted by the frequency mixer 52 with a predetermined narrow band frequency, and outputs a voltage having a target frequency. The peak detection circuit 54 detects the peak of the output of the second RF filter 2, and the output is held at a constant time constant for stabilization. The comparator 55 compares the output of the peak detection circuit 54 with a predetermined value, and the comparison result is sent to the digital signal processing unit 1.

  The frequency fs of the output signal of the frequency mixer 52 is the frequency of the output sine wave of the sine wave generation circuit 56 (hereinafter referred to as sine wave frequency) fs and the frequency fa of the output signal of the first RF filter 51 (unbalanced component signal). Since the sum (fs + fa) and the difference (fs−fa) are obtained, by changing at least one of the frequency fa of the output sine wave and the center frequency (hereinafter referred to as passband frequency) fr of the passband of the second RF filter 54, It is possible to know the strength of the signal of the specific frequency of the balanced component signal. For example, when the sine wave frequency is set to fs1 and the passband frequency is set to fr1 (where fs1> fr1), the signal indicating the strength of the unbalanced component signal frequency fa1 (= fs1-fr1) is the second RF Output from the filter 54.

  Therefore, the state of the unbalanced component signal of a specific frequency can be detected by the digital signal processing unit 1 based on the signal of the comparator 55. For example, when the unbalanced component is equal to or greater than a predetermined value, Leakage power from the transmission lines 61 and 62 can be reduced by reducing the output power of the carrier or performing processing that does not use it.

  The frequency at which the strength of the unbalanced component (the magnitude of the leakage power) should be determined is set by the detection frequency setting unit 11, and the determination control unit 12 determines the sine wave frequency fs and the passband frequency according to the set frequency. At least one of fr is changed.

  Note that the peak detection circuit 54 can be omitted, and an AD converter may be provided instead of the comparator 55, and the output digital value of the second RF filter 53 may be input to the digital signal processing unit 1. A low speed AD converter is sufficient here. In that case, the digital signal processing unit 1 changes the generation process of the digital transmission signal according to the input digital value.

  Next, a schematic operation of the communication apparatus of FIG. 1 will be described. At the time of signal transmission, the digital transmission signal generated by the digital signal processing unit 1 is converted into an analog signal by the DA converter 21a of the AFE chip 21, and the communication transformer is passed through the transmission filter 22, the transmission amplifier 23, and the transmission switch 24. To drive. And it is output from the transmission lines 61 and 62 connected to the secondary side of the communication transformer 3.

  The unbalanced components of the transmission lines 61 and 62 at the time of transmission are detected by the unbalanced component detection unit 4, and the strength of the unbalanced component of the predetermined frequency (the magnitude of the leakage power) is determined by the leakage power determination unit 5. The The unbalanced component is detected when a non-modulated (sine wave) multicarrier signal is transmitted.

  At the time of signal reception, the reception signals from the transmission lines 61 and 62 are sent to the reception filter 25 via the communication transformer 3, and after the gain adjustment of the reception AGC amplifier 26 is performed, the reception AD converter 21b of the AFE chip 21 is performed. Is converted into a digital signal, and the digital signal processing unit 1 converts it into digital data. At this time, the transmission switch 24 is in an off state.

  Next, operations of the detection frequency setting unit 11 and the determination control unit 12 will be described in more detail. As described above, by changing at least one of the sine wave frequency fs and the passband frequency fr, it is possible to determine the strength (magnitude of leakage power) of an unbalanced component of an arbitrary frequency. 11, the selection of the frequency to be determined and the determination timing can be appropriately designed according to the operation mode of the communication system.

(Set frequency to be judged)
The frequency to be determined is set according to the country where the balanced transmission system is to be installed. Since the length of the indoor wiring used for power line communication can be estimated according to the situation of each country house, a frequency band that is likely to leak is obtained from the resonance frequency based on the length. Then, it is stored in association with each country as priority detection frequency band information for which leakage power should be determined with priority on the frequency band.

  The detection frequency setting unit 11 outputs corresponding priority detection frequency band information to the determination control unit 12 when there is an instruction from the outside of the system installation country. When such setting is performed, it is possible to determine the leakage power efficiently for each country of installation.

  The detection frequency setting unit 11 estimates the length of the transmission line based on the reception strength at the communication partner, obtains the priority detection frequency band based on the resonance frequency of the transmission line having the estimated length, and obtains the obtained priority detection. The frequency band may be a frequency band to be detected. In this case, it is necessary to obtain information on the reception intensity from the reception partner.

  Further, the detection frequency setting unit 11 outputs a frequency band in which leakage power has been large in the past to the determination control unit 12 as a frequency band to be detected. In this case, leakage power in all communication bands is detected in advance at an appropriate timing.

(Judgment timing, etc.)
When the frequency to be determined is set, the determination corresponding to the state of the transmission lines 61 and 62 can be performed by determining the leakage power not only for the frequency but also for the nearby frequencies. For example, the strength of the unbalanced component (magnitude of leakage power) of a slightly higher frequency and a slightly lower frequency around the set frequency is determined at a frequency slightly lower than the center frequency. Corresponding to the change in the state of the transmission line that makes such a determination, it is possible to quickly perform a process for reducing the leakage power.

  Moreover, it is preferable to determine unbalanced power for all frequencies at an appropriate timing regardless of the set frequency. In this case, the frequency band with a large leakage power is determined by sweeping the sine wave frequency and determining the output of the second RF filter 53 at that time.

  The present invention provides a line state detection device that can quickly determine the state of unbalanced power in a required frequency band of a transmission line in a balanced transmission system that performs data transmission using a pair of conductors with a simple configuration. Useful as such. Further, it is useful as a communication device of a balanced transmission system that can control the balanced state of the transmission line based on the detection result and can improve the balance.

The figure which shows schematic structure of the communication apparatus for describing embodiment of this invention 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 1 ... Digital signal processing part 2 ... Analog circuit part 3 ... Communication transformer 4 ... Unbalanced component detection part 5 ... Leakage power determination part 11 ... Detection frequency setting part 12 ... Determination control unit 21... Analog front end chip 21a... Transmission DA converter 21b... Reception AD converter 22... Transmission filter 23 .. transmission amplifier 24. Filter 26 ... Reception AGC amplifier 51 ... First RF filter 52 ... Frequency mixer 53 ... Second RF filter 54 ... Peak detection circuit 55 ... Comparator 56 ... Sine wave generation circuit 61, 62 ... conductor (transmission line)

Claims (12)

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,
Detecting an unbalanced component between the pair of conductors and outputting an unbalanced component signal corresponding to the unbalanced component ;
A sine wave signal generator for generating a sine wave signal;
A frequency mixer for mixing the sinusoidal signal and the unbalanced component signal;
A bandpass filter to which an output signal of the frequency mixer is input;
A detection frequency band information holding unit for holding priority detection frequency band information according to a country in which the balanced transmission system is installed;
A determination control unit that controls at least one of the generated sine wave frequency of the sine wave signal generator and the pass frequency band of the band pass filter based on the priority detection frequency band information;
A leakage power determination unit that determines a magnitude of the leakage power based on an output of the band pass filter after at least one of the sine wave generation frequency and the pass frequency band is controlled by the determination control unit. Line state detection device. The line state detection device according to claim 1,
The leakage power determination unit is a line state detection device that determines the magnitude of the leakage power based on the unbalanced component signal when an unmodulated multicarrier signal is transmitted. The line state detection device according to claim 1 ,
The determination control unit is a line state detection device that sweeps a generated sine wave frequency of the sine wave signal generator. The line state detection device according to claim 1 ,
A detection frequency setting unit for setting a frequency band in which the leakage power is to be detected;
The determination control unit is a line state detection device that controls at least one of a generated sine wave frequency of the sine wave signal generator and a pass frequency band of the band pass filter based on the set frequency band. The line state detection device according to claim 4 ,
The detection frequency setting unit estimates the length of the transmission line based on the reception intensity at the communication partner, obtains the priority detection frequency band based on the resonance frequency of the transmission line of the estimated length, and obtains the obtained priority detection frequency band A line state detection device that outputs to the determination control unit as a frequency band to be detected. The line state detection device according to claim 4 ,
The said detection frequency setting part is a line state detection apparatus which outputs to the said determination control part as a frequency band which should detect the frequency band which leakage power was large in the past. The line state detection device according to any one of claims 1 to 6 ,
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 any one of claims 1 to 6 ,
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 8 ,
The pair of conductors is a line state detection device which is a power line. A communication device used in a balanced transmission system that performs data transmission using a pair of conductors,
A communication apparatus provided with the track | line state detection apparatus of any one of Claim 1 thru | or 9 . A balanced transmission system that performs data transmission using a pair of conductors,
A balanced transmission system comprising the communication device according to claim 10 . A line state detection method for detecting a state of a transmission line in a balanced transmission system that performs data transmission using a pair of conductors,
Detecting the unbalanced components between the pair of conductors, and unbalanced component detection step of outputting unbalanced component signal corresponding to the unbalanced component,
A sine wave signal generating step for generating a sine wave signal;
A frequency mixing step of mixing the sinusoidal signal and the unbalanced component detection signal;
A band-passing step in which an output signal output from the frequency mixing step is input;
A detection frequency band information holding step for holding priority detection frequency band information according to a country in which the balanced transmission system is installed;
A determination control step of controlling at least one of the generated sine wave frequency of the sine wave signal and the pass frequency band of the band pass step based on the priority detection frequency band information;
A line state detection method comprising: a leakage power determination step of determining a magnitude of the leakage power based on an output of the band pass filter after at least one of the sine wave generation frequency and the pass frequency band is controlled .

Images