JP2006262217A - Power line measurement instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a measurement instrument capable of acquiring the characteristic of a transmission path without forming a closed circuit under environment causing signal reflection and attenuation in a particular frequency band such as a power line. <P>SOLUTION: In the power line measurement instrument for measuring a transmission characteristic between two points on the transmission path of the power line, a transmitter side generates a frequency sweeping signal of 2 to 40 MHz, injects the frequency sweeping signal to the transmission path, and extracts a reproduction timing signal from the frequency sweeping signal obtained from the transmission path by using a corrector such as asliding correlator and a matched filter. Then a receiver side controls so that a frequency sweeping signal for reference prepared in advance is synchronized with the frequency sweeping signal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power transmission path measuring device in a power line carrier system.

  In high-frequency signal transmission (power line carrier) using a power line, the transmission side and the reception side are not directly connected one-on-one like a communication cable. Various devices such as a panel, a power meter, or a home appliance are present. For this reason, it is known that the impedance frequently changes in the transmission path, causing reflection and attenuation of the high-frequency signal. Therefore, since transmission characteristics (line quality) are different for each transmission path, the transmission characteristics of individual transmission paths must be acquired in advance when installing the power line carrier device.

Usually, a measuring instrument called a network analyzer is used to obtain transmission characteristics of a power line. FIG. 5 shows an example of acquiring power line transmission characteristics using a network analyzer. In FIG. 5, the frequency sweep signal output from the network analyzer is injected into the power line via a device such as an injector and a coupling unit, and the frequency sweep signal propagated through the power line is returned to the network analyzer via the coupling unit and extractor. By forming a closed circuit, the transmission characteristics of the power line are acquired.
However, if the transmission path is extremely long, the measurement cable must be lengthened accordingly, which necessitates the insertion of an amplifier on the way, resulting in a large-scale measurement system. In addition, when the length of the transmission line is extremely long, such as several hundred meters, it is practically impossible to form a closed circuit by installing a measurement cable between the power line and the network analyzer.

In view of this, a method for measuring the characteristics of a transmission line without forming a closed circuit even when the transmission line becomes extremely long is disclosed in Japanese Patent Laid-Open No. 8-163010.
According to the technique disclosed in JP-A-8-163010, a transmission device and a reception device are connected to an input end and an output end of a transmission line, respectively, and a measurement signal that changes at a predetermined frequency step is transmitted from the transmission device. This is analyzed by the receiving device. Here, it is necessary to synchronize the timing of frequency sweep on the transmission device side and the timing of changing the analysis frequency on the reception side.
Therefore, synchronization is achieved by superimposing a signal subjected to FM modulation with a synchronization signal on a specific carrier frequency (pilot channel) on the transmission side, and FM demodulating it on the reception side.
JP-A-8-163010

However, in the conventional transmission path measurement method disclosed in Japanese Patent Laid-Open No. 8-163010, since the carrier frequency of the pilot channel is fixed, if this is applied to the measurement of the power line, the synchronization signal cannot be demodulated on the receiving side. There is a fear. As described above, signal reflection and attenuation frequently occur on the transmission line of the power line. For this reason, if the frequency band that attenuates on the transmission path matches the carrier frequency of the pilot channel, the receiving side cannot demodulate the synchronization signal, and transmission characteristics cannot be acquired. In addition, since the frequency band to be attenuated varies depending on the transmission path, it is practically impossible to set the carrier frequency of the pilot channel so as to avoid it from the attenuation frequency band.
The present invention has been made in order to solve the above-described problems. In an environment where signal reflection or attenuation occurs in a specific frequency band such as a power line, the characteristics of the transmission line can be obtained without forming a closed circuit. An object of the present invention is to provide an acquirable measuring device.

In order to solve the above-mentioned problem, according to the first aspect of the present invention, there is provided an apparatus for measuring frequency transmission characteristics between two points on a power transmission line, which is electromagnetically coupled to a part of the power transmission line and is subjected to frequency sweeping. A first coupling unit that injects a signal; a second coupling unit that electromagnetically couples with a portion of the power transmission path to extract the frequency sweep signal; and the frequency sweep in the first coupling unit. An oscillation unit for supplying a signal; and a measurement unit for analyzing the frequency of the frequency sweep signal extracted from the second coupling and measuring the frequency transmission characteristic,
The oscillating unit includes a timing generation unit that outputs a predetermined timing signal, and a frequency sweep unit that generates a frequency sweep signal that sweeps a frequency linearly in synchronization with the timing signal. A timing extraction unit that extracts a reproduction timing signal synchronized with the timing signal from a frequency sweep signal supplied from the second coupling unit; and the frequency sweep signal at an analysis timing synchronized with the reproduction timing signal. Frequency analysis means for analyzing the frequency components contained in the signal and the signal intensity thereof, and display means for displaying the analysis contents of the frequency analysis means.

According to a second aspect of the present invention, in the first aspect, the timing extracting means includes a reference signal generating means for generating a reference signal for linearly sweeping the frequency, and the reference signal and the frequency sweep signal. And a correlator for detecting a cross-correlation, wherein the reference signal generating means outputs the reproduction timing signal obtained by detecting the cross-correlation between the reference signal and the frequency sweep signal by the correlator. And the reference signal sweep timing is controlled to synchronize the sweep timing of the reference signal with the sweep timing of the frequency sweep signal.
According to a third aspect of the present invention, in the second aspect, the correlator is a sliding correlation circuit or a matched filter circuit.

  The present invention is an apparatus for measuring transmission characteristics between two points on the transmission line of a power line. A frequency sweep signal of 2 to 40 MHz is generated on the transmission side, injected into the transmission line, and taken out from the transmission line. A reproduction timing signal is extracted from the frequency sweep signal using a correlator such as a sliding correlator or a matched filter, and based on this, a reference frequency sweep signal prepared in advance on the receiving side is synchronized with the frequency sweep signal. Thus, it is unnecessary to form a closed loop, and even when an attenuation frequency band exists in the transmission line, there is an effect in providing a measuring device that can stably acquire the frequency transmission characteristics of the transmission line.

The present invention will be described based on the embodiments shown in the drawings.
FIG. 1 shows a block diagram of a power line measuring apparatus according to the present invention.
The power line measuring apparatus according to the present invention includes an oscillation unit 1 that generates a high-frequency frequency sweep signal as a signal generation source, and a coupling that electromagnetically couples a part of the power line 2 and injects the frequency sweep signal into the power line 2. A unit 3 (first coupling unit), a coupling unit 4 (second coupling unit) that electromagnetically couples with a part of the power line 2 and takes in a frequency sweep signal injected into the power line 2; A measuring unit 5 is provided that analyzes and displays the frequency component and the intensity of the frequency sweep signal extracted from the coupling unit 4.

  The oscillating unit 1 also includes a temperature-compensated crystal oscillator 6 (timing generator) that generates a timing signal having a predetermined frequency, and a ramp voltage generator that generates a voltage (ramp voltage) that changes linearly in synchronization with the timing signal. Unit 7, a frequency sweeper 8 that generates a frequency sweep signal that linearly sweeps the output frequency in accordance with the ramp voltage output by the ramp voltage generator 7, and an amplifier 9 that amplifies the frequency sweep signal to a predetermined level; And switching means 10 for switching the output impedance of the amplifier 9 to either 50Ω balanced or 50Ω unbalanced.

  The measuring unit 5 switches the input impedance to either 50Ω balanced or 50Ω unbalanced and connects to the coupling unit 4 and the frequency sweep signal supplied from the switching unit 11 to a predetermined level. An amplifier 12 to be amplified, a timing extraction unit 13 for extracting a timing reproduction signal synchronized with the timing signal from a frequency sweep signal amplified by the amplifier 12, and a voltage (ramp that changes linearly in synchronization with the timing reproduction signal) Voltage), and a frequency analysis unit 15 that analyzes the frequency component included in the frequency sweep signal and its signal intensity at an analysis timing according to the lamp voltage supplied from the lamp voltage generation unit 14. And a display unit 16 for displaying the analysis result of the frequency analysis unit 15.

The power line measuring apparatus according to the present invention shown in FIG. 1 operates as follows.
First, the temperature compensated crystal oscillator 6 generates a timing signal having a predetermined frequency. In synchronization with this timing signal, the ramp voltage generator 7 repeatedly generates a ramp voltage that varies linearly. For example, the ramp voltage linearly changes in the voltage range from Vstart to Vstop and is repeated in synchronization with the timing signal.
Therefore, the frequency sweeper 8 generates a frequency sweep signal that linearly sweeps the output frequency according to the ramp voltage. For example, the frequency range of 2 to 40 MHz is linearly swept every cycle (synchronized with the timing signal) that is a multiple of 50 Hz.
The frequency sweep signal is amplified to a predetermined level by the amplifier 9, and the output impedance is converted to 50Ω balanced by the switching means 10 and supplied to the coupling unit 3.

Next, the frequency sweep signal supplied to the coupling unit 3 is injected into the power line 2, propagates through the power line 2, and is extracted from the coupling unit 4 and then supplied to the measurement unit 5.
The measuring unit 5 receives the frequency sweep signal extracted from the coupling unit 4 in a state where the input impedance is in a balanced state of 50Ω, and the switching unit 11 supplies it to the amplifier 12.
The amplifier 12 amplifies the frequency sweep signal and supplies it to the timing extraction unit 13 and the frequency analysis unit 15.

  Here, the timing extraction unit 13 will be described. The timing extraction unit 13 includes a reference signal generating means (not shown) for generating a reference signal having substantially the same frequency sweep characteristic as that of the frequency sweep signal, and a correlator for detecting a cross-correlation between the reference signal and the frequency sweep signal. (Not shown). A correlator such as a sliding correlator or a matched filter can be used as the correlator.

  The timing extraction unit performs a process of reducing noise by adding the amplified frequency sweep signals as shown in FIG. Therefore, a cross-correlation between the frequency sweep signal with reduced noise and the reference frequency sweep signal is detected by the correlator, and a point at which the reference signal and the frequency sweep signal are synchronized is searched by the correlator. When the synchronization point is found, the correlator outputs a signal (reproduction timing signal) synchronized with the timing signal generated by the oscillation unit 1. The reproduction timing signal is fed back to the reference signal generating means to control the frequency sweep timing of the reference signal, and the sweep timing of the reference signal is controlled to be synchronized with the sweep timing of the frequency sweep signal.

The ramp voltage generator 14 generates a ramp voltage that varies linearly according to the reproduction timing signal. This ramp voltage is synchronized with that generated by the ramp voltage generator of the oscillator 1. The frequency analysis unit 15 analyzes the frequency component of the frequency sweep signal and its signal intensity at the analysis timing according to the lamp voltage. For example, as shown in FIG. 3, the measurement unit 5 (frequency analysis unit 16) synchronizes with the lamp voltage, and f1, f2, f3, f4 in the frequency range of 2 to 40 MHz at times t1, t2, t3, and t4. The signal strengths of the frequency components are sequentially calculated, and this is repeated after time t5. Of course, the number of frequencies to be analyzed may be increased.
Next, when the data analyzed by the frequency analysis unit 16 is output to the display unit 16, the signal strength of the frequency component included in the frequency sweep signal is displayed, and the frequency characteristic as the transmission line of the power line can be acquired.

In addition, since the frequency sweep signal sweeps the frequency range of 2 to 40 MHz, even if there is a frequency band that attenuates in the transmission line, only a part of the frequency band is attenuated as shown in FIG. The unit 5 can stably maintain synchronization.
In contrast, in the conventional measuring apparatus, as shown in FIG. 4B, since the synchronization signal is fixed at a specific carrier frequency, it is impossible to maintain synchronization if an attenuation frequency band exists in the vicinity of the carrier frequency. It becomes possible. Therefore, it is clear that the present invention is excellent.

In this embodiment, the interface with the coupling units 3 and 4 is 50Ω balanced. However, the present embodiment is not limited to this, and the switching means 10 and 11 is set to 50Ω according to the interface of the coupling unit. It is possible to switch to the unbalanced side and connect a coupling unit here.
As described above, the present invention uses the correlator such as the sliding correlator and the matched filter to generate the reference signal synchronized with the frequency sweep signal inside the measurement unit. Even if it occurs, it is effective to provide a measuring device that can stably acquire the transmission characteristics of the power line.

The block diagram which showed the Example of the measuring apparatus of the power line which concerns on this invention. Operation | movement explanatory drawing of the measurement part of the measuring apparatus of the power line which concerns on this invention. Operation | movement explanatory drawing of the measurement part of the measuring apparatus of the power line which concerns on this invention. The figure which showed the frequency sweep signal which propagates a power line transmission line. The block diagram of the measuring apparatus of the conventional power line transmission path.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Oscillator 2 ... Power line 3, 4 ... Coupling unit 5 ... Measuring unit 6 ... Temperature compensation crystal oscillator 7, 14 ... Lamp voltage generator 8 ... Frequency sweeper 9, 12 ... Amplifier 10 11, switching means 13, timing extraction unit 15, frequency analysis unit 16, display unit

Claims (3)

An apparatus for measuring frequency transmission characteristics between two points on a power transmission path,
A first coupling unit that electromagnetically couples to a part of the power transmission path and injects a frequency sweep signal; and a second cup that electromagnetically couples to a part of the power transmission path and extracts the frequency sweep signal. A ring unit; an oscillation unit that supplies the frequency sweep signal to the first coupling unit; and a measurement unit that analyzes the frequency of the frequency sweep signal extracted from the second coupling and measures the frequency transmission characteristics. Prepared,
The oscillating unit includes a timing generation unit that outputs a predetermined timing signal, and a frequency sweep unit that generates a frequency sweep signal that linearly sweeps the frequency in synchronization with the timing signal.
The measurement unit includes timing extraction means for extracting a reproduction timing signal synchronized with the timing signal from a frequency sweep signal supplied from the second coupling unit, and the frequency at an analysis timing synchronized with the reproduction timing signal. A power line measuring apparatus comprising: frequency analysis means for analyzing frequency components included in a sweep signal and signal intensity thereof; and display means for displaying analysis contents of the frequency analysis means. The timing extraction means includes a reference signal generation means for generating a reference signal for linearly sweeping a frequency, and a correlator for detecting a cross-correlation between the reference signal and the frequency sweep signal, The reproduction timing signal obtained by detecting the cross-correlation between the reference signal and the frequency sweep signal by the correlator is fed back to the reference signal generating means to control the sweep timing of the reference signal, and the reference 2. The power line measuring apparatus according to claim 1, wherein a signal sweep timing is synchronized with a sweep timing of the frequency sweep signal. 3. The power line measuring apparatus according to claim 2, wherein the correlator is a sliding correlation circuit or a matched filter circuit.

Images