JP4743622B2 - Power line measuring instrument - Google Patents

Description

  The present invention relates to a power line measuring device, and more particularly to a power line measuring device that predicts the transmission speed of the power line under measurement based on the S / N value of each frequency of the power line under measurement.

  In the transmission of high-frequency signals using power lines, the transmission side and the reception side are not directly connected one-on-one like a communication cable, but connected to a branch of the transmission path, transformer, distribution board, watt hour meter, or outlet Depending on the frequency, attenuation and impedance changes may occur depending on the home appliances used, the signal injection / extraction method, and the installation location. And since there are countless combinations of these, it is indispensable for the power line carrier device to perform line design and field confirmation according to the transmission path conditions.

  In addition, when measuring the characteristics of a transmission line using a general-purpose measuring instrument, a network analyzer is used. However, since one device shares the transmitting side and the receiving side, either signal is opposed by a coaxial cable. It is necessary to stretch to the point. FIG. 7 is a configuration diagram of a measurement system using a conventional network analyzer. This system includes a network analyzer 50, an injector 51 that injects a signal transmitted from the network analyzer 50 into a power line 55 through a coupling unit 54, and an extractor 52 that extracts a signal from the power line 55 through a coupling unit 53. And comprising. In this system, since the transmission side and the reception side are shared by one network analyzer 50, for example, it is necessary to extend the signal on the transmission side to the opposite location with the coaxial cable 56.

Further, as a prior art that attempts to overcome the same problem, Patent Document 1 discloses a transmission path characteristic measuring apparatus that provides a pilot channel (frequency) subjected to FM modulation for synchronization and generates a timing signal from a demodulation result. It is disclosed.
Patent Document 2 discloses a method using an arbitrary waveform generator and a digital oscilloscope.
JP-A-8-163010 JP 2004-354155 A

However, in a measurement system using a conventional network analyzer, the measurement range is limited by the length of the coaxial cable 56, and the scale of measurement equipment becomes large, such as the need for an amplifier. There is a problem that it is not suitable for time use.
Also, since there is currently no dedicated equipment that can easily measure the transmission line of the power line, an approximate circuit design is carried out from the wiring diagram and installation drawing, the spectrum analyzer and the power line carrier equipment are replaced on-site at the optimum frequency, and various There is a problem that it takes a lot of time for the installation work because it is installed while switching and confirming the setting.

In the case of a power line, the prior art disclosed in Patent Document 1 is not suitable for a power line because it is expected that a pilot signal does not reach the receiving side due to various frequency characteristics due to branching or connection of home appliances.
Further, since the conventional technique disclosed in Patent Document 2 is intended for high-precision measurement, there is a problem in that it is not easy to use in the field and the transmission characteristics of the power line carrier device cannot be measured.

In view of this problem, the present invention transmits an OFDM signal as a reference signal from an oscillation unit via a power line to be measured and receives the signal based on the S / N value of each subcarrier when the signal is received by the measurement unit. An object of the present invention is to provide a power line measuring instrument that can easily measure the transmission path characteristics and the usable transmission speed by calculating and estimating the transmission path characteristics and the usable transmission speed of the measurement power line.
Another object is to make the oscillation unit and the measurement unit small and light, thereby making the shape suitable for carrying.

In order to solve the above-mentioned problem, the present invention determines the appropriate bandwidth of the modem based on the S / N value of the power line when installing a repeater and a modem used for power line transmission. A power line measuring device that provides information to be generated, an oscillation unit that generates an OFDM signal having a plurality of subcarriers in a predetermined frequency band as a reference signal and injects the OFDM signal into the power line to be measured, and the power line to be measured A measurement unit that receives the OFDM signal transmitted through the subcarrier and calculates a use band of the modem according to an S / N value of each subcarrier, and the oscillation unit generates at least the OFDM signal An OFDM modulation unit, an oscillation side coupling unit for injecting the OFDM signal into the power line to be measured, and an interface corresponding to the oscillation side coupling unit An oscillation-side interface conversion circuit that selects the measurement-side coupling unit that extracts the OFDM signal from the power line to be measured, and a measurement that selects an interface corresponding to the measurement-side coupling unit. Side interface conversion circuit, a frequency analysis unit for analyzing the frequency component of the OFDM signal received from the oscillation unit, a storage unit for storing waveform data necessary for measurement, an OFDM signal received from the oscillation unit, and the storage unit A calculation unit that calculates the transmission speed of the power line to be measured, a display unit that displays a calculation result by the calculation unit, and a control unit based on the waveform data stored in To do.
The basic configuration of the measuring instrument of the present invention is an oscillating unit and a measuring unit, and a power line to be measured is connected between them. Then, the OFDM signal is transmitted from the oscillating unit to the power line, and the use band of the modem is calculated according to the S / N value of the OFDM signal received by the measuring unit. The OFDM (orthogonal frequency division multiplex) signal is an abbreviation for orthogonal frequency division multiplex system, in which a large number of carriers are orthogonalized between adjacent carriers, and a part of the carrier band is overlapped to effectively use the frequency band. It is a method to do.
The oscillation unit modulates and amplifies the OFDM signal and injects it into the power line via the coupling unit. Moreover, the peak value of each frequency of the OFDM signal received from the power line via the coupling unit is stored. Then, the noise signal stored in advance and the received peak value are calculated by the calculation unit to obtain the S / N value, and the transmission rate of each frequency is calculated based on the modulation value that can be used with the S / N value.

According to a second aspect of the present invention, the control unit includes at least the transmission spectrum of the oscillating unit, the noise spectrum existing on the power line to be measured, the maximum value of the OFDM signal received from the oscillating unit, the number of subcarriers, the frequency The modulation degree switching S / N value data calculated from the modulation degree and the allowable error rate is stored.
In order for the calculation unit to perform various calculations, it is necessary to store a base reference signal. For example, in order to calculate the transmission line characteristic, the transmission spectrum of the oscillation unit is stored in advance, and the difference from the reception spectrum attenuated by the power line is calculated to obtain the transmission line characteristic. Further, by storing the noise spectrum of the power line when the OFDM signal is not transmitted from the oscillation unit, the S / N value of each frequency can be calculated.

According to a third aspect of the present invention, when the transmission path characteristic display operation is performed, the control unit calculates a difference between the transmission spectrum stored in the storage unit and the maximum value of the OFDM signal received from the oscillation unit, The calculation unit is controlled to display a calculation result on the display unit.
The transmission line characteristics of the power line are the same as the transmission spectrum transmitted from the oscillation side if there is no attenuation. However, there is actually no attenuation at all, and attenuation occurs according to each frequency. Therefore, when display operation of the transmission path characteristics is performed from the operation unit, the control unit calculates the difference between the reference transmission spectrum stored in the storage unit and the maximum value of the OFDM signal received from the oscillation unit, The result is displayed on the display unit.

According to a fourth aspect of the present invention, when the S / N display operation is performed, the control unit subtracts the noise spectrum stored in the storage unit from the OFDM signal of each frequency analyzed by the frequency analysis unit, The calculation unit is controlled to display a calculation result on the display unit.
The OFDM signal of each frequency analyzed by the frequency analysis unit is stored in the storage unit. Since the noise spectrum is also stored in the storage unit, the S / N value of each frequency is calculated by subtracting both signals.

According to a fifth aspect of the present invention, when a transmission speed prediction display operation is performed, the control unit subtracts the noise spectrum stored in the storage unit from an OFDM signal for each frequency analyzed by the frequency analysis unit. The S / N value for each subcarrier is calculated, the modulation degree usable in each subcarrier is obtained from the calculated S / N value, the values of all subcarriers are totaled, and the calculation result is displayed on the display unit. The arithmetic unit is controlled to display.
When the S / N value for each subcarrier is calculated, the degree of modulation that can be used for each subcarrier is obtained. For example, it is required that 16QAM (4 bits) data transmission is possible at a certain frequency. Finally, the values of all subcarriers are added up to estimate the transmission rate of the transmission path.

  According to the present invention, an oscillating unit that generates a wideband OFDM signal as a reference signal and injects the OFDM signal into the power line to be measured, and receives the OFDM signal transmitted through the power line to be measured and receives the S of each subcarrier. Since the measurement unit for calculating the use band of the modem according to the / N value is provided, the transmission path characteristics and the usable transmission speed can be easily measured without being restricted by the measurement range.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the components, types, combinations, shapes, relative arrangements, and the like described in this embodiment are merely illustrative examples and not intended to limit the scope of the present invention only unless otherwise specified. .
FIG. 1 is an internal block diagram of a power line measuring device according to an embodiment of the present invention. This power line measuring apparatus 100 broadly generates a broadband OFDM signal as a reference signal and injects the OFDM signal into the power line 9 to be measured, and the OFDM signal transmitted via the power line 9 to be measured. And a measuring unit 10 that calculates a use band of the modem according to the S / N value of each subcarrier.

  The oscillation unit 1 includes a pseudo data generation unit 2 that generates pseudo data, an OFDM modulation unit 3 that generates an OFDM signal, a D / A converter 4 that converts OFDM into an analog signal, and a signal converted into an analog signal. LPF 5 for removing unnecessary harmonics included in the amplifier, an amplifier 6, an oscillation side interface conversion circuit 7 for selecting an interface corresponding to the oscillation side coupling unit 8, and an oscillation side for injecting an OFDM signal into the power line 9 to be measured A measurement unit 10 that extracts an OFDM signal from the power line 9 to be measured, and a measurement side interface conversion circuit that selects an interface corresponding to the measurement side coupling unit 11. 12, the amplifier 13, and the frequency component of the OFDM signal received from the oscillation unit 1 are analyzed. Frequency analysis unit 14, storage unit 16 that stores waveform data necessary for measurement, OFDM signal received from oscillation unit 1, and waveform data stored in storage unit 16, A calculation unit 17 that calculates a transmission speed, a display unit 19 that displays a calculation result by the calculation unit 17, an operation unit 18 that instructs display, and a control unit 15 that controls the entire measurement unit are configured. Yes. In the present embodiment, the 50Ω balanced side is selected for the oscillation side interface conversion circuit 7 and the measurement side interface conversion circuit 12.

Next, an outline of the present invention will be described before a detailed description of the power line measuring device of FIG. FIG. 2 is a diagram illustrating an example of noise characteristics of the power line to be measured. The performance of power lines as transmission paths varies. In addition, the noise component superimposed on the power line varies depending on the type and number of home appliances used. For example, in the power line of FIG. 2A, noise having a high noise level exists in a high frequency band (example 1). In FIG. 2B, noise having a high noise level exists in both the low frequency band and the high frequency band (example 2). Further, in FIG. 2C, it can be seen that the noise level is low over the entire band (there are few such examples) (example 3). As described above, the noise characteristics vary depending on the power line, and these characteristics vary depending on time and season. However, in the case of PLC, it is impossible to determine where the subcarrier band of the modem is set unless the noise characteristics of the power line are actually measured.
Therefore, when the noise characteristics of FIGS. 2A to 2C are known in advance by measurement, the use band of the modem is set as shown in FIG. That is, in the case of Example 1, since the noise level in the low frequency band is low as shown in FIG. 3A, the use band of the modem is set to this band (Setting A). In the case of Example 2, since the noise level in the frequency band near the center is low as shown in FIG. 3B, the use band of the modem is set to this band (Setting B). In the case of Example 3, since the noise level of the entire frequency band is low as shown in FIG. 3C, the use band of the modem is set to the entire band (Setting C).

Even if the modem communicates in a noisy band, errors increase, and as a result, the transmission speed of the channel decreases because retransmission is repeated. In other words, the efficiency is reduced and data can be transmitted only a little for using power. Thus, ideally, a large number of bits can be transmitted by transmitting with setting C, but actually, setting A and setting B are used according to the state of the power line.
For example, 4 bits of data can be transmitted when the modulation factor at setting A is 16QAM (Quadrature Amplitude Modulation), 7 bit data can be transmitted when the modulation factor at setting B is 128 QAM, and When the modulation degree is 256QAM, 8-bit data can be transmitted. As described above, the power line measuring instrument according to the present invention depends on the transmission line characteristics and noise (S / N) of the power line when installing the PLC repeater (device on the power pole) and the modem (each household device). It is a measuring instrument for judging in advance which setting to use.

  FIG. 4 is a diagram for explaining the measurement procedure of the power line measuring instrument of the present invention. (A) is a schematic configuration diagram of measurement, (b) is a diagram of a transmission signal and a reception signal, and (c) is a diagram of noise. As shown in FIG. 4A, the measured power line 9 is connected between the oscillating unit 1 and the measuring unit 10, and nothing is interposed between them in order to simplify the description. As shown in FIG. 4B, a transmission signal 20 (waveform A), which is a reference signal, is transmitted from the oscillating unit 1 to the power line 9 to be measured, attenuated during transmission of the power line 9 to be measured, and received by the measuring unit 10. 21 (waveform B) is received. The level of each waveform B varies depending on the transmission characteristics of the power line 9 to be measured. Here, if the waveform A is known in advance, the transmission characteristic of the power line 9 to be measured is determined by (waveform A)-(waveform B). This characteristic is preferable as the level is high and the fluctuation for each frequency is small (flat). 4C, the noise waveform 22 (waveform C) existing in the power line 9 to be measured is measured on the measurement unit 10 side when the transmission signal is turned off from the oscillation unit 1. Then, the S / N value of each subcarrier is known from (waveform B)-(waveform C).

  FIG. 5 is a graph showing the S / N value of each subcarrier. The horizontal axis is the frequency, and the vertical axis is the S / N value. The higher the value, the better the S / N. As can be seen from this figure, in the subcarrier (Q point) with good S / N, the modulation density can be increased (for example, 256 QAM), and a high transmission rate can be obtained. Further, in the subcarrier (P point) having a poor S / N, the modulation density must be lowered (for example, 16QAM), and therefore only a low transmission rate can be obtained. Therefore, the transmission rate of the power line 9 to be measured can be estimated by adding the transmission rates of all the subcarriers.

  FIG. 6 is a flowchart showing a measurement procedure of the power line measuring device according to the embodiment of the present invention. A description will be given with reference to FIG. A noise spectrum existing in the power line 9 to be measured is stored in advance in the storage unit 16 of the measurement unit 10 (S1). In this state, the OFDM signal is injected from the oscillating unit 1 into the power line 9 to be measured through the coupling unit 8 (S13). The injected OFDM signal is transmitted through the power line 9 to be measured and extracted through the coupling unit 11 (S2). Similar to the spectrum analyzer, the measurement unit 10 sweeps the received signal at regular intervals, and in order to remove errors due to level fluctuations due to the OFDM signal pattern, only the maximum value of each frequency is taken into the storage unit 16 for each sweep. Store (S3). The measurement frequency point is preferably 400 points or more in order to obtain the transmission line frequency characteristics.

  Next, the transmission spectrum of the oscillating unit 1 is stored in the storage unit 16 in advance, and when the measurer performs a display operation of the transmission path characteristics by the operation unit 18 (YES route in S4), the calculation unit 17 The difference between the stored received waveforms is calculated (S5), and the calculation result is displayed on the display unit 19 (S6). Next, when the measurer performs an S / N display operation with the operation unit 18 (YES route in S7), the calculation unit 17 subtracts the noise spectrum stored in the storage unit 16 from the reception reference signal data of each frequency ( S8), the calculation result is displayed on the display unit 19 (S9). Next, when the measurer performs a transmission speed prediction display operation with the operation unit 18 (YES route in S10), the noise spectrum stored in the storage unit 16 from the OFDM signal for each frequency analyzed by the frequency analysis unit 14 Is subtracted to calculate the S / N value for each subcarrier, the modulation degree usable in each subcarrier is obtained from the calculated S / N value, the values of all subcarriers are totaled (S11), The calculation result is displayed on the display unit 19 (S12).

As described above, according to the present invention, an oscillation unit 1 that generates a broadband OFDM signal as a reference signal and injects the OFDM signal into the power line to be measured, and an OFDM signal transmitted through the power line 9 to be measured are received. And a measurement unit 10 that calculates the use band of the modem according to the S / N value of each subcarrier, so that the transmission path characteristics and the usable transmission speed can be easily measured without being restricted by the measurement range. be able to.
Further, the oscillating unit 1 modulates and amplifies the OFDM signal and injects it into the power line 9 to be measured via the coupling unit 8. In addition, the peak value of each frequency of the OFDM signal received from the power line 9 to be measured via the coupling unit 11 is stored, the noise signal stored in advance and the received peak value are calculated by the calculation unit 17, and S / Since the N value is obtained and the transmission rate of each frequency is calculated based on the modulation value that can be used with the S / N value, the accurate transmission rate for each frequency can be estimated.

The storage unit 16 has at least the transmission spectrum of the oscillation unit 1, the noise spectrum present on the power line 9 to be measured, the maximum value of the OFDM signal received from the oscillation unit 1, the number of subcarriers, the frequency, the modulation factor, and the allowable values. Since the data of the modulation degree switching S / N value calculated from the error rate is stored, it can be easily calculated from the OFDM signal received by the measuring unit 10, and the waveform data can be analyzed in detail later. it can.
In addition, when the transmission path characteristic display operation is performed, the control unit 15 calculates the difference between the transmission spectrum stored in the storage unit 16 and the maximum value of the OFDM signal received from the oscillation unit 1, and calculates the calculation result. Since the calculation unit 17 is controlled so as to display on the display unit 19, the transmission characteristics can be displayed in real time.

When the S / N display operation is performed, the control unit 15 subtracts the noise spectrum stored in the storage unit 16 from the OFDM signal of each frequency analyzed by the frequency analysis unit 14 and displays the calculation result. Since the calculating part 17 is controlled so that it displays on the part 19, the S / N value for every subcarrier can be displayed in real time.
In addition, when the transmission speed prediction display operation is performed, the control unit 15 subtracts the noise spectrum stored in the storage unit 16 from the OFDM signal of each frequency analyzed by the frequency analysis unit 14 to obtain the S for each subcarrier. / N value is calculated, the degree of modulation available for each subcarrier is obtained from the calculated S / N value, the values of all subcarriers are totaled, and the calculation result is displayed on the display unit 19 Since the unit 17 is controlled, the transmission rate for each subcarrier can be displayed in real time.

It is an internal block diagram of the power line measuring device which concerns on embodiment of this invention. It is a figure which shows an example of the noise characteristic of a to-be-measured power line. It is a figure explaining the setting of the use band of a modem. It is a figure explaining the measurement procedure of the power line measuring device of the present invention. It is the figure which graphed the S / N value of each subcarrier. It is a flowchart which shows the measurement procedure of the power line measuring device which concerns on embodiment of this invention. It is a block diagram of the measurement system using the conventional network analyzer.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Oscillation part, 2 pseudo data generation part, 3 OFDM modulation part, 4 D / A converter, 5 LPF, 6 amplifier, 7 Oscillation side interface conversion circuit, 8 Oscillation side coupling unit, 9 Measured power line, 10 measurement part , 11 Measuring side coupling unit, 12 Measuring side interface conversion circuit, 13 Amplifier, 14 Frequency analysis unit, 15 Control unit, 16 Storage unit, 17 Calculation unit, 18 Operation unit, 19 Display unit, 100 Power line measuring instrument

Claims (5)

A power line measuring instrument for providing information for determining an appropriate bandwidth for use of a modem based on an S / N value of a power line when installing a repeater and a modem used for power line transmission,
An oscillation unit that generates an OFDM signal having a plurality of subcarriers in a predetermined frequency band as a reference signal and injects the OFDM signal into the power line to be measured, and receives the OFDM signal transmitted through the power line to be measured And a measuring unit that calculates a use band of the modem according to the S / N value of each subcarrier ,
The oscillation unit includes at least an OFDM modulation unit that generates the OFDM signal;
An oscillation side coupling unit that injects the OFDM signal into the power line to be measured, and an oscillation side interface conversion circuit that selects an interface corresponding to the oscillation side coupling unit, and
The measurement unit includes a measurement-side coupling unit that extracts the OFDM signal from the measured power line;
A measurement side interface conversion circuit for selecting an interface corresponding to the measurement side coupling unit;
A frequency analysis unit for analyzing a frequency component of the OFDM signal received from the oscillation unit;
A storage unit for storing waveform data necessary for measurement;
Based on the OFDM signal received from the oscillating unit and the waveform data stored in the storage unit, a calculation unit that calculates the transmission speed of the power line to be measured;
A display unit for displaying a calculation result by the calculation unit;
And a control unit .   The control unit includes at least a transmission spectrum of the oscillation unit in the storage unit, a noise spectrum existing in the power line to be measured, a maximum value of an OFDM signal received from the oscillation unit, the number of subcarriers, a frequency, a modulation degree, and The power line measuring device according to claim 1, wherein data of switching S / N value of modulation degree calculated from an allowable error rate is stored.   When the transmission path characteristic display operation is performed, the control unit calculates a difference between the transmission spectrum stored in the storage unit and the maximum value of the OFDM signal received from the oscillation unit, and displays the calculation result in the display The power line measuring device according to claim 1, wherein the calculation unit is controlled so as to be displayed on the unit.   When the S / N display operation is performed, the control unit subtracts the noise spectrum stored in the storage unit from the OFDM signal of each frequency analyzed by the frequency analysis unit, and displays the calculation result in the display The power line measuring instrument according to claim 1, wherein the calculation unit is controlled so as to be displayed on the unit. When the transmission speed prediction display operation is performed, the control unit subtracts the noise spectrum stored in the storage unit from the OFDM signal for each frequency analyzed by the frequency analysis unit, and performs S for each subcarrier. / N value is calculated, the modulation degree usable in each subcarrier is obtained from the calculated S / N value, the values of all subcarriers are totaled, and the calculation result is displayed on the display unit. The power line measuring instrument according to claim 1, 2, 3, or 4, wherein the arithmetic unit is controlled.

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