JP3646879B2 - Line characteristic measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a line characteristic measuring apparatus for a communication line such as a telephone line for communicating high-speed digital data, and more particularly to a line characteristic measuring apparatus capable of displaying a line model and displaying the line characteristic after eliminating a failure factor.
[0002]
[Prior art]
In conventional communication lines such as telephone lines, transmission characteristics such as attenuation characteristics, noise characteristics, TDR (Time Domain Reflectometer: hereinafter referred to as TDR), characteristic impedance, line resistance, line capacity, loopback resistance, etc. Measure.
[0003]
FIG. 21 is a block diagram showing the configuration of an example of such a conventional line characteristic measuring apparatus. In FIG. 21, 1 is a line to be measured to be measured, 2 is a switching means, 3, 4 and 5 are various line characteristics such as attenuation characteristics, noise characteristics, TDR, characteristic impedance, line resistance, line capacity, loopback resistance and the like. Measuring means for measuring, 6 a control means, and 7 a display means such as a CRT (Cathode Ray Tube) or LCD (Liquid Crystal Display).
[0004]
The output of the line under test 1 is connected to the switching means 2, and the plurality of outputs of the switching means 2 are connected to the measuring means 3, 4 and 5, respectively. The outputs of the measuring means 3, 4 and 5 are connected to the display means 7, respectively.
[0005]
Further, the control output of the control means 6 is connected to the control input terminals of the switching means 2, measuring means 3, 4 and 5, respectively.
[0006]
Here, the operation of the conventional example shown in FIG. 21 will be described with reference to FIG. 22, FIG. 23 and FIG. 22 is a characteristic curve diagram showing a display example of the attenuation characteristic on the display means 7, FIG. 23 is a characteristic curve diagram showing a display example of the characteristic impedance on the display means 7, and FIG. 24 is a display example of TDR on the display means 7. FIG.
[0007]
The control means 6 controls the switching means 2 to appropriately switch the output of the line under test 1 and input it to the various measuring means 3, 4 or the measuring means 5, and control the measuring means 3 to the measuring means 5 to display various characteristic curves. Displayed on the display means 7.
[0008]
For example, if the measuring means 3 is an attenuation characteristic measuring means, an attenuation characteristic curve as shown by “CH01” in FIG.
[0009]
For example, similarly, if the measuring means 4 and 5 are characteristic impedance and TDR measuring means, the display means 7 displays a characteristic impedance characteristic as shown by “CH11” in FIG. 23, and “CH21” in FIG. A TDR measurement waveform as shown is displayed.
[0010]
As a result, the control means 6 appropriately switches various measuring means to measure the required line characteristics, and displays the various line characteristics measured on the display means 7, thereby allowing the engineer to display the various line characteristics displayed. It becomes possible to grasp the status of the line to be measured 1.
[0011]
[Problems to be solved by the invention]
However, in the conventional example shown in FIG. 21, the individual line characteristics are displayed as they are on the display means 7 as shown in FIGS. 22 to 24. Therefore, unless the engineer understands the characteristics of the line to be measured 1, There was a problem that it was difficult to fully grasp the situation.
[0012]
Further, although an excellent engineer can determine the state of the line from one line characteristic, there is a problem that it is difficult to identify the cause.
[0013]
For example, although the location of the impedance change point can be grasped from the TDR waveform, whether the impedance change is due to the influence of the bridge tap or the lightning arrester, POTS (Plain Old Telephone System: hereinafter simply referred to as POTS) It cannot be determined whether it is a splitter or a hand-twisted connection point.
Therefore, the problem to be solved by the present invention is to realize a line characteristic measuring apparatus capable of estimating and displaying a line model based on measurement characteristics and estimating and displaying line characteristics after failure factor elimination and the like. There is.
[0014]
[Means for Solving the Problems]
In order to achieve such a problem, the invention according to claim 1 of the present invention is:
In a line characteristic measuring device for communication lines,
Switching means for switching the output destination of the line to be measured; a plurality of measuring means for measuring various line characteristics connected to a plurality of outputs of the switching means; and a control means for controlling the switching means and the plurality of measuring means; The display means and the analysis means for estimating the line model based on the various line characteristics measured by the plurality of measurement means and drawing the display means on the display means, thereby estimating and displaying the line model based on the measurement characteristics This makes it possible to accurately and easily grasp the line status even if the user is not familiar with the line characteristics.
[0015]
The invention according to claim 2
In the line characteristic measuring apparatus according to claim 1,
The analysis means is
Line length specifying means for specifying the line length of the line to be measured based on line resistance applied from a plurality of measuring means, and line model drawing means for estimating and drawing a line model using the obtained line length; This makes it possible to estimate and display the line model based on the measurement characteristics, and to easily and accurately grasp the line state without being familiar with the line characteristics. .
[0016]
The invention described in claim 3
In the line characteristic measuring apparatus according to claim 1,
The analysis means is
Bridge tap detection specifying means for determining the presence or absence of a bridge tap of the line under test based on various line characteristics applied from a plurality of the measurement means, and for obtaining a bridge tap length and a bridge tap position when a bridge tap exists. And a line model drawing means for estimating and drawing a line model using the obtained bridge tap length and the bridge tap position, thereby estimating and displaying the line model based on the measurement characteristics. It is possible to accurately and easily grasp the state of the line even if the user is not familiar with the line characteristics.
[0017]
The invention according to claim 4
In the line characteristic measuring apparatus according to claim 3,
The bridge tap detection specifying means is
If two line lengths based on line resistance and line capacity applied from a plurality of measurement means are not equal, it is determined that a bridge tap exists on the line to be measured, and the bridge tap length is determined from the difference between the two line lengths. Therefore, it is possible to estimate and display the line model based on the measurement characteristics, and to easily and accurately grasp the line state even if the user is not familiar with the line characteristics.
[0018]
The invention according to claim 5
In the line characteristic measuring apparatus according to claim 3,
The bridge tap detection specifying means is
If there is a depression in the attenuation characteristics applied from the plurality of measuring means, it is determined that a bridge tap exists on the line to be measured, and the bridge tap length is obtained from the frequency of the depression due to the resonance that appears first. As a result, it is possible to estimate and display the line model based on the measurement characteristics, and it is possible to easily and accurately grasp the line state even if the user is not familiar with the line characteristics.
[0019]
The invention described in claim 6
In the line characteristic measuring apparatus according to claim 3,
The bridge tap detection specifying means is
When a depression exists in the attenuation characteristics applied from the plurality of measuring means, it is determined that a bridge tap on the line to be measured exists, and the bridge tap length is obtained from an average value of frequency intervals of the depression due to resonance. As a result, it is possible to estimate and display the line model based on the measurement characteristics, and it is possible to easily and accurately grasp the line state without being familiar with the line characteristics.
[0020]
The invention described in claim 7
In the line characteristic measuring apparatus according to claim 3,
The bridge tap detection specifying means is
Determine whether or not a bridge tap exists on the line under measurement using time domain reflection method, and obtain and display the line model based on the measurement characteristics by obtaining the bridge tap length and the bridge tap position. This makes it possible to accurately and easily grasp the line status even if the user is not familiar with the line characteristics.
[0021]
The invention described in claim 8
In the line characteristic measuring device according to claim 7,
The bridge tap detection specifying means is
When a reflected wave is detected as the reverse polarity of the incident pulse, it is determined that a bridge tap exists on the line to be measured, and a line model is determined based on measurement characteristics by obtaining the bridge tap position from the position of the reflected wave. It is possible to estimate and display, and it is possible to easily and accurately grasp the state of the line without being familiar with the characteristics of the line.
[0022]
The invention according to claim 9
In the line characteristic measuring device according to claim 8,
The bridge tap detection specifying means is
Based on the measurement characteristics, the position of the far end of the bridge tap is obtained from the position of the second reflected wave detected as the same polarity of the incident pulse, and the bridge tap length is obtained from the difference from the bridge tap position. The line model can be estimated and displayed, and the line state can be easily and accurately grasped even if the user is not familiar with the line characteristics.
[0023]
The invention according to claim 10 is:
In the line characteristic measuring apparatus according to claim 3,
The bridge tap detection specifying means is
By determining that there is a possibility that a bridge tap on the line to be measured exists when resonance of characteristic impedance applied from a plurality of the measurement means is interference at a low impedance point, a line model based on the measurement characteristics Can be estimated and displayed, and the state of the line can be accurately and easily grasped even if the user is not familiar with the characteristics of the line.
[0024]
The invention according to claim 11
In the line characteristic measuring apparatus according to claim 1,
The analysis means is
A noise source estimating means for estimating a noise source by comparing noise characteristics applied from a plurality of measuring means and a spectrum profile of a noise source registered in advance, and a line model using the estimated noise source. It is possible to estimate and display the line model based on the measurement characteristics and to accurately display the line status even if you are not familiar with the line characteristics. It becomes possible to grasp it well and easily.
[0025]
The invention according to claim 12
In the line characteristic measuring apparatus according to claim 1,
The analysis means is
Based on the low frequency resonance characteristics applied from the plurality of measuring means, the number of loaded wire rings existing on the line to be measured and the loaded wire ring detection specifying means for obtaining the position thereof, the number of obtained loaded wire rings, It is composed of a line model drawing means that estimates and draws a line model by using the position, which makes it possible to estimate and display a line model based on measurement characteristics, and is familiar with the line characteristics. Even without it, it is possible to easily and accurately grasp the line status.
[0026]
The invention according to claim 13
In a line characteristic measuring device for communication lines,
Switching means for switching the output destination of the line to be measured; a plurality of measuring means for measuring various line characteristics connected to a plurality of outputs of the switching means; and a control means for controlling the switching means and the plurality of measuring means; The display means, and the analysis means for estimating the line characteristics after eliminating the cause of the failure or the noise source based on the various line characteristics measured by the plurality of measuring means and drawing on the display means. Based on this, it is possible to estimate and display the line characteristics after the failure factor elimination and the like, and to grasp the line characteristics after the failure factor elimination, so that the improvement effect can be estimated.
[0027]
The invention according to claim 14
In the line characteristic measuring apparatus according to claim 13,
The analysis means is
Specific spectrum removal means for removing a spectrum caused by a failure factor from the various line characteristics, calculation means for performing inverse FFT conversion on the characteristic from which the spectrum output from the specific spectrum removal means has been removed, and output of the calculation means Establishing and displaying the line characteristics after eliminating the cause of failure based on the measured characteristics by configuring the line characteristics drawing means to estimate and draw the line characteristics after eliminating the cause of failure by adding to the theoretical curve It is possible to grasp the line characteristics after eliminating the cause of failure, etc., so that the improvement effect can be estimated.
[0028]
The invention according to claim 15
In the line characteristic measuring apparatus according to claim 13,
The analysis means is
Specific spectrum removing means for removing a spectrum of noise caused by a noise source from the various line characteristics, and line characteristic drawing means for removing the noise level at a neighboring frequency of the spectrum and estimating and drawing the line characteristics after eliminating the noise source It is possible to estimate and display the line characteristics after eliminating the cause of failure based on the measured characteristics, and to grasp the line characteristics after eliminating the cause of failure so that the improvement effect is estimated. be able to.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a line characteristic measuring apparatus according to an embodiment of the present invention. In FIG. 1, 1, 2, 3, 4, 5, 6 and 7 are assigned the same reference numerals as in FIG. 21, and 8 is an analysis means.
[0030]
The output of the line under test 1 is connected to the switching means 2, and the plurality of outputs of the switching means 2 are connected to the measuring means 3, 4 and 5, respectively. The outputs of the measuring means 3, 4 and 5 are connected to the analyzing means 8, and the output of the analyzing means 8 is connected to the display means 7.
[0031]
Further, the control output of the control means 6 is connected to the control input terminals of the switching means 2, measuring means 3, 4 and 5, respectively.
[0032]
Here, the schematic operation of the embodiment shown in FIG. 1 will be described with reference to FIG. FIG. 2 is a flowchart for explaining the operation of the line characteristic measuring apparatus.
[0033]
In "S001" in FIG. 2, the control means 6 controls the switching means 2 to appropriately switch the output of the circuit under test 1 and input it to the various measuring means 3, 4 or the measuring means 5, and the measuring means 3 to 5 Control is performed to output various characteristic curves to the analysis means 8.
[0034]
For example, if the measuring means 3 is a measuring means for attenuation characteristics, an attenuation characteristic curve is output to the analyzing means 8. Similarly, if the measurement means 4 and 5 are characteristic impedance and TDR measurement means, the characteristic impedance characteristic and the TDR measurement waveform are output to the analysis means 8.
[0035]
In “S002” in FIG. 2, the analyzing means 8 estimates the line model of the line to be measured 1 from various measurement results and displays it on the display means 7.
[0036]
For example, the analysis means 8 specifies the position of the bridge tap of the line to be measured 1 and its distance from various measurement results and displays them on the line model, or specifies the cause of the generated noise and determines the line model. Or display it on top.
[0037]
In “S003” in FIG. 2, the analysis unit 8 estimates the line characteristics after eliminating the cause of the failure such as a bridge tap and the noise source, and displays them on the display unit 7.
[0038]
As a result, it is possible to estimate and display the line model based on the measured various line characteristics, and to estimate and display the line characteristics after eliminating the failure factor.
[0039]
Here, the details of the operation for estimating the channel model of the embodiment shown in FIG. 1 are shown in FIG. 3, FIG. 4, FIG. 5, FIG. 6, FIG. FIG. 13, FIG. 14, FIG. 15, FIG. 16 and FIG.
[0040]
FIG. 3 is a block diagram showing the details of the line model estimation function of the analyzing means 8, FIG. 4 is a flowchart explaining the operation of the analyzing means 8 when estimating the line model, and FIG. 5 is an explanation showing the estimated line model. FIG. 6, FIG. 6 is a characteristic curve diagram showing an example of the measured attenuation characteristic, FIG. 7 is a characteristic curve diagram relating to the difference between the theoretical value and the actual measurement value of the attenuation characteristic, and FIG. 8 is the result of FFT conversion of the characteristic curve of FIG. FIG.
[0041]
9 and 10 are characteristic curve diagrams showing examples of TDR waveforms, FIG. 11 is a characteristic curve diagram showing characteristic impedance interference at a low impedance point, and FIG. 12 is a characteristic curve showing characteristic impedance interference at a high impedance point. FIG.
[0042]
Further, FIG. 13 is a characteristic curve diagram illustrating a noise source estimation method, FIG. 14 is a characteristic curve diagram illustrating an example of a low-frequency resonance characteristic, FIG. 15 is a circuit diagram illustrating an example of a loaded wire ring resonance model, and FIG. FIG. 17 is an explanatory diagram showing an estimated line model.
[0043]
In FIG. 3, 9 is a line length specifying means, 10 is a bridge tap detection specifying means, 11 is a noise source estimating means, 12 is a loaded wire ring detection specifying means, and 13 is a line model drawing means.
[0044]
The output from the measuring means for measuring the line resistance is applied to the line length specifying means 9, and the output from the measuring means for measuring the line resistance, the line capacity, the attenuation characteristic and the TDR is applied to the bridge tap detection specifying means 10. .
[0045]
Further, the output from the measuring means for measuring the noise characteristics is applied to the noise source estimating means 11, and the output from the measuring means for measuring the low frequency resonance characteristics is applied to the loaded wire ring detection specifying means 12.
[0046]
The outputs of the line length specifying means 9, the bridge tap detection specifying means 10, the noise source estimating means 11 and the loaded wire ring detection specifying means 12 are respectively output to the line model drawing means 13, and the output of the line model drawing means 13 is the display means 7. Is output.
[0047]
In “S101” in FIG. 4, the line length specifying means 9 specifies the line length of the line under test 1 based on the applied line resistance. That is, since the line length not including the bridge tap is obtained from the line resistance, the line length is obtained based on the measured line resistance of the line under measurement 1.
[0048]
In “S102” in FIG. 4, the bridge tap detection specifying means 10 determines whether or not a bridge tap exists in the line under test 1.
[0049]
If a bridge tap exists, the bridge tap detection specifying means 10 obtains the length of the bridge tap (bridge tap length) in “S103” in FIG. 4, and the location where the bridge tap exists in “S104” in FIG. (Bridge tap position) is obtained. On the other hand, if there is no bridge tap, the process jumps to the step “S105” in FIG.
[0050]
For example, as a first determination method, as described above, the line length not including the bridge tap is obtained from the line resistance, while the line length including the bridge tap is obtained from the line capacity. If the lengths are equal, there is no bridge tap on the line under test 1.
[0051]
Conversely, if the line lengths of both are not equal, a bridge tap exists on the line under measurement 1.
[0052]
That is, assuming a line model as shown in FIG. 5, a line length of “4 km” is obtained from the line resistance, and a line length of “4.5 km” is obtained from the line capacity. There will be a bridge tap. The bridge tap length “500 m” can be obtained from the difference between the two.
[0053]
As a second determination method, for example, there is a method of determining the presence or absence of a bridge tap on the line under measurement 1 based on whether or not there is a dip in the measured attenuation characteristic.
[0054]
That is, when an actual measurement characteristic as shown in “CH42” in FIG. 6 is obtained with respect to a theoretical curve as shown in “CH41” in FIG. 6, periodic depressions (Dip) are recognized. A bridge tap exists on the measurement line 1.
[0055]
Here, when the calculation of further subtracting the theoretical value from the actually measured value and multiplying the Hamming window is performed, the result is as shown in FIG. 7, and when the characteristic of FIG.
[0056]
In the characteristic curve indicated by “CH51” in FIG. 7, the frequency (about 80 kHz) of the dip (Dip) due to resonance appearing at the first time as indicated by “PT51” in FIG. 7 is “f”, the light velocity is “C”, and the light velocity. Assuming that the ratio of propagation speed in the line to "VOP (Velocity of Propagation)", the bridge tap length "L" _BT "
L _BT = (VOP × C) / 4f (1)
Can be obtained from
[0057]
Similarly, in the characteristic curve indicated by “CH61” in FIG. 8, assuming that the average value (about 170 kHz) of the frequency interval of the depression (Dip) as indicated by “PT61” in FIG. "L _BT "
L _BT = (VOP × C) / 2fint (2)
Can be obtained from
[0058]
If there are a plurality of bridge taps having different bridge tap lengths, a plurality of peaks of the characteristic curve shown in FIG. 8 appear.
[0059]
As a third determination method, for example, there is a method of determining the presence and position of a bridge tap using TDR.
[0060]
That is, since the reflected wave from the bridge tap is reflected from a low impedance, it is detected as the reverse polarity of the incident pulse.
[0061]
For example, in the TDR waveform indicated by “CH71” in FIG. 9, when a reflected wave having a reverse polarity as indicated by “RF71” in FIG. 9 is recognized with respect to the incident pulse indicated by “PL71” in FIG. The position of the bridge tap can be obtained from the position of the wave.
[0062]
On the other hand, the reflected wave from the far end of the bridge tap is reflected from the open end, and is detected as the same polarity of the incident pulse.
[0063]
For example, in the TDR waveform indicated by “CH81” in FIG. 10, when a reflected wave having the same polarity as that indicated by “RF81” in FIG. 10 is recognized with respect to the incident pulse indicated by “PL81” in FIG. It becomes possible to obtain the position of the far end of the bridge tap from the position of the wave.
[0064]
That is, the difference between the distance to the far end of the bridge tap and the distance to the bridge tap corresponds to the bridge tap length.
[0065]
Furthermore, as a fourth determination method, for example, there is a method of determining the presence or absence of a bridge tap based on the presence or absence of resonance of characteristic impedance and the waveform shape.
[0066]
That is, when interference exists in the characteristic impedance from the telephone station side, it is determined whether the interference is at the low impedance point or the high impedance point.
[0067]
For example, when the characteristic impedance is “CH91” in FIG. 11, interference occurs at a low impedance point. When the characteristic impedance is “CH101” in FIG. This means that interference occurs.
[0068]
If interference occurs at a low impedance point, there is a possibility that a bridge tap exists. Therefore, the TDR measurement is performed as described above, and the polarity and level of the reflected wave in the TDR, as well as the impedance data. Based on the above, the presence or absence of a bridge tap is determined.
[0069]
In “S105” in FIG. 4, the noise source estimation means 11 estimates the noise source by performing a pattern matching of the measured noise pattern and the pre-registered noise source spectrum.
[0070]
For example, the characteristic curve indicated by “CH111” in FIG. 13 is a profile of an ISDN (Integrated Services Digital Network) signal crosstalk spectrum, while the characteristic curve indicated by “CH112” in FIG. 13 is an actual measurement in the presence of ISDN crosstalk noise. Line noise.
[0071]
In this manner, in the characteristic curve diagram shown in FIG. 13, since the actually measured line noise approximates the spectrum profile of the noise source registered in advance, the noise source estimation means 11 regards the noise as ISDN crosstalk noise. Can be estimated.
[0072]
Further, it is possible to compare the noise characteristics on the telephone station side and the noise characteristics on the home side and analyze the superimposed noise level to estimate the noise superimposition location. For example, when the noise level on the telephone station side and the house side are the same level, a noise source exists at an intermediate point between the telephone station and the house, or at the entire line.
[0073]
In “S106” in FIG. 4, the loaded wire ring detection specifying means 12 measures the low-frequency resonance characteristics, and obtains the number and positions of the loaded wire rings existing on the line to be measured 1.
[0074]
Here, the loading ring is also called “Loading Coil”, and it has a large land area of “66 mH” in order to suppress the attenuation of voice signals in the United States, Canada, etc. where the land is wide and the distance from the telephone office to the home is long. An inductance is loaded.
[0075]
The resonance between this inductance and the line capacitance (50 pF / m) causes a peak at “about 2 kHz to 4 kHz” to suppress the attenuation of the audio signal. ADSL (Asymmetric Digital Subscriber Line) using a band of “30 kHz” or more is fatal.
[0076]
That is, the loaded wire ring detection specifying unit 12 measures the low frequency resonance characteristics and specifies the number of loaded wire wheels from the number of local minimum points. For example, in the characteristic curve indicated by “CH121” in FIG. 14, there are three minimum points at the points indicated by “PT121”, “PT122”, and “PT123” in FIG. become.
[0077]
On the other hand, as the position of the loading wire ring, the line frequency capacity of the line is obtained by simultaneous equations of the resonance frequency at the resonance point of the minimum point, and the distance to the loading wire ring is obtained from the value.
[0078]
In the resonance model of the loaded wire wheel shown in FIG. 15, the inductance values shown in “L1”, “L2” and “L3” in FIG. 15 are known, and “C1”, “C2” and “C3” in FIG. And the capacitance between the lines indicated by “C4” is obtained by the above-described calculation.
[0079]
Since the line capacity is proportional to the line length (50 pF / m), it is possible to obtain the distance from the line capacity of the line to the loaded wire ring.
[0080]
For example, when the line model shown in FIG. 16 is estimated from the resonance model shown in FIG. 15, the lines indicated by “LC131”, “LC132” and “LC133” in FIG. There are two loading lines, and the distance “DS131” from the telephone station indicated by “CO131” in FIG. 16 to the loading line indicated by “LC131” in FIG. 16 is obtained from the line capacity indicated by “C1” in FIG. .
[0081]
Further, the distance “DS132” from the loading wire ring indicated by “LC131” in FIG. 16 to the loading wire ring indicated by “LC132” in FIG. 16 is obtained from the line capacity indicated by “C2” in FIG.
[0082]
Further, the distance “DS133” from the loading wire ring indicated by “LC132” in FIG. 16 to the loading wire ring indicated by “LC133” in FIG. 16 is obtained from the line capacity indicated by “C3” in FIG.
[0083]
Finally, the distance “DS134” from the loaded wire wheel indicated by “LC133” in FIG. 16 to the home indicated by “CP131” in FIG. 16 is obtained from the line capacity indicated by “C4” in FIG.
[0084]
In “S107” in FIG. 4, the line model drawing means 13 uses the line length obtained by the line length identifying means 9, the bridge tap length obtained by the bridge tap detection identifying means 10, the position of the bridge tap, and the noise source estimating means 11. The line model is estimated and drawn using the noise source estimated in step (1), the number of loaded wire rings and the position of the loaded wire ring obtained by the loaded wire ring detection specifying means 12.
[0085]
For example, from the line model shown in FIG. 17, the line to be measured indicated by “LN141” in FIG. 17 whose line length is “DS141” is long from the telephone station indicated by “CO141” in FIG. It can be seen that there is a bridge tap “BT141” having a length of “BL141”.
[0086]
Similarly, from the line model shown in FIG. 17, the measured line shown as “LN141” in FIG. 17 has a bridge tap with a length of “BL142” at a distance “DS143” from the home shown as “CP141” in FIG. 17. It can be seen that “BT142” exists.
[0087]
Further, it can be seen from the line model shown in FIG. 17 that the loaded wire ring indicated by “LC141” in FIG. 17 exists at the position “DS144” from the telephone station indicated by “CO141” in FIG.
[0088]
Finally, from the line model shown in FIG. 17, there is a noise source (for example, ISDN near-end crosstalk noise) as shown in “NZ141” in FIG. 17 in the vicinity of the telephone station shown in “CO141” in FIG. It can be seen that there is a noise source (for example, AM (amplitude modulation) noise) as indicated by “NZ142” in FIG. 17 in the vicinity of the house indicated by “CP141”.
[0089]
As a result, the line model is estimated and drawn on the basis of the information obtained by the line length specifying means 9, the bridge tap detection specifying means 10, the noise source estimating means 11 and the loaded wire ring detecting specifying means 12, thereby Even if you are not familiar with the characteristics, you can easily and accurately grasp the line status.
[0090]
Details of the operation for estimating the line characteristics after eliminating the cause of failure in the embodiment shown in FIG. 1 will be described with reference to FIGS.
[0091]
FIG. 18 is a block diagram illustrating the details of the line characteristic estimation function of the analyzing means 8, FIG. 19 is a flowchart illustrating the operation of the analyzing means 8 when estimating the line characteristics after eliminating the failure factor, and FIG. It is a flowchart explaining the operation | movement at the time of the channel | line characteristic estimation after specific noise source exclusion.
[0092]
In FIG. 18, 14 is a specific spectrum removing means, 15 is a computing means, and 16 is a line characteristic drawing means. The output from the measuring means for measuring the line resistance, line capacity, attenuation characteristic, noise characteristic, low frequency resonance characteristic and TDR is applied to the specific spectrum removing means 14.
[0093]
The output of the specific spectrum removing unit 14 is connected to the calculating unit 15, and the output of the calculating unit 15 is connected to the line characteristic drawing unit 16. The output of the line characteristic drawing means 16 is connected to the display means 7.
[0094]
In “S201” in FIG. 19, the specific spectrum removing unit 14 removes the spectrum caused by the failure factor, and in “S202” in FIG. 19, the computing unit performs inverse FFT transform on the characteristic from which the spectrum has been removed.
[0095]
In "S203" in FIG. 19, the line characteristic drawing means 16 adds the result of inverse FFT change to the theoretical curve to estimate and draw the line characteristic after eliminating the failure factor.
[0096]
For example, by removing the spectrum as indicated by “PT61” in FIG. 8 due to the bridge tap that is the cause of the failure, performing inverse FFT conversion, and adding to the theoretical curve as indicated by “CH41” in FIG. It is possible to estimate and draw the line characteristics after eliminating the factors.
[0097]
Further, in “S301” in FIG. 20, the specific spectrum removing means 14 removes the spectrum of noise caused by a specific noise source (for example, AM noise source). In “S302” in FIG. The noise level is removed at the neighboring frequency, and the line characteristic after the noise source is eliminated is estimated and drawn.
[0098]
As a result, the failure factor such as a bridge tap and the noise source are removed, and the channel characteristic is estimated by calculation, so that the channel characteristic after the failure factor is eliminated can be grasped, so that the improvement effect can be estimated.
[0099]
In addition, as a measuring means, what measures various line characteristics, such as attenuation characteristics, noise characteristics, TDR, characteristic impedance, line resistance, line capacity, and loopback resistance, is illustrated, but other line characteristics are measured. Of course, it doesn't matter.
[0100]
In the description of FIG. 3, the line length specifying means 9, the bridge tap detection specifying means 10, the noise source estimating means 11 and the loaded wire ring detection specifying means 12 are added to the line model drawing means 13. Any one or more of the specifying unit 9, the bridge tap detection specifying unit 10, the noise source estimation unit 11, and the loaded wire ring detection specifying unit 12 may be added to the line model drawing unit 13.
[0101]
Further, regarding the removal of the noise source, the AM noise is exemplified, but the other noise sources can be similarly performed. For example, in the case of TCM (Time Compression Multiplex) -ISDN noise, the specific spectrum removing unit 14 removes the spectrum based on the noise spectrum obtained at the FEXT (Far End Cross Talk) timing.
[0102]
In the case of broadband noise, the noise level after removing the noise source of the broadband noise cannot be estimated, so the noise level after removing the noise source of the broadband noise is the input conversion noise spectrum of the modem. By assuming that it is “−140 dBm / Hz”, it is possible to estimate the line characteristics after eliminating the noise source.
[0103]
Also, by eliminating the loading wire ring, the characteristic impedance and attenuation characteristics of the line under measurement are mainly improved. With respect to the attenuation characteristic, as described in “Japanese Patent Application No. 2000-314775” relating to the applicant of the present application, it is possible to estimate the characteristic curve from the line length and the wire diameter.
[0104]
Further, the noise spectrum, attenuation characteristics, and S / N ratio can be calculated, and the transmission rate can also be calculated from the calculated S / N ratio.
[0105]
【The invention's effect】
As is apparent from the above description, the present invention has the following effects.
According to the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh and twelfth aspects of the invention, the line length specifying means, the bridge tap detection specifying means, the noise source estimating means or the loading By estimating and displaying the line model based on the information obtained by the ring ring detection specifying means, etc., it becomes possible to accurately and easily grasp the line state without being familiar with the line characteristics. .
[0106]
In addition, according to the inventions of claims 13, 14 and 15, after removing the cause of trouble, etc., by removing the cause of the trouble such as a bridge tap and the noise source and estimating and displaying the line characteristic by calculation. Therefore, the improvement effect can be estimated.
[Brief description of the drawings]
FIG. 1 is a configuration block diagram showing an embodiment of a line characteristic measuring apparatus according to the present invention.
FIG. 2 is a flowchart for explaining the operation of the line characteristic measuring apparatus.
FIG. 3 is a configuration block diagram illustrating details of a line model estimation function of an analysis unit.
FIG. 4 is a flowchart for explaining the operation of the analysis means at the time of channel model estimation.
FIG. 5 is an explanatory diagram showing an estimated line model.
FIG. 6 is a characteristic curve diagram showing an example of measured attenuation characteristics.
FIG. 7 is a characteristic curve diagram relating to a difference between a theoretical value and an actual measurement value of an attenuation characteristic.
8 is a characteristic curve diagram showing the result of FFT conversion of the characteristic curve of FIG.
FIG. 9 is a characteristic curve diagram showing an example of a TDR waveform.
FIG. 10 is a characteristic curve diagram showing an example of a TDR waveform.
FIG. 11 is a characteristic curve diagram showing interference of characteristic impedance at a low impedance point.
FIG. 12 is a characteristic curve diagram showing interference of characteristic impedance at a high impedance point.
FIG. 13 is a characteristic curve diagram illustrating a noise source estimation method.
FIG. 14 is a characteristic curve diagram showing an example of a low frequency resonance characteristic.
FIG. 15 is a circuit diagram showing an example of a resonance model of a loaded wire ring.
FIG. 16 is an explanatory diagram showing an estimated line model;
FIG. 17 is an explanatory diagram showing an estimated line model;
FIG. 18 is a block diagram illustrating the details of the line characteristic estimation function of the analysis means.
FIG. 19 is a flowchart for explaining the operation at the time of channel characteristic estimation after the failure factor is eliminated by the analyzing means.
FIG. 20 is a flowchart for explaining the operation at the time of channel characteristic estimation after the AM noise source is eliminated by the analysis means.
FIG. 21 is a configuration block diagram showing an example of a conventional line characteristic measuring apparatus.
FIG. 22 is a characteristic curve diagram showing a display example of attenuation characteristics.
FIG. 23 is a characteristic curve diagram showing a display example of characteristic impedance.
FIG. 24 is a characteristic curve diagram illustrating a display example of TDR.
[Explanation of symbols]
1 Line under test
2 Switching means
3, 4, 5 Measuring means
6 Control means
7 Display means
8 Analysis means
9 Line length identification means
10 Bridge tap detection identification means
11 Noise source estimation means
12 Loaded wire ring detection identification means
13 Line model drawing means
14 Specific spectrum removal means
15 Calculation means
16 Line characteristic drawing means

Claims (15)

In a line characteristic measuring device for communication lines,
Switching means for switching the output destination of the line under test;
A plurality of measuring means for measuring various line characteristics connected to a plurality of outputs of the switching means;
Control means for controlling the switching means and the plurality of measuring means;
Display means;
A line characteristic measuring apparatus comprising: an analyzing unit that estimates a line model based on various line characteristics measured by the plurality of measuring units and causes the display unit to draw the model. The analysis means is
Line length specifying means for specifying the line length of the line under test based on line resistance applied from a plurality of the measuring means;
2. The line characteristic measuring apparatus according to claim 1, further comprising: a line model drawing means for estimating and drawing a line model using the obtained line length. The analysis means is
A bridge tap detection specifying means for determining the presence or absence of a bridge tap of the line under test based on various line characteristics applied from a plurality of the measurement means, and for determining a bridge tap length and a bridge tap position when a bridge tap exists; ,
2. The line characteristic measuring apparatus according to claim 1, further comprising line model drawing means for drawing a line model by using the obtained bridge tap length and the bridge tap position. The bridge tap detection specifying means is
If two line lengths based on line resistance and line capacity applied from a plurality of measurement means are not equal, it is determined that a bridge tap exists on the line to be measured, and the bridge tap length is determined from the difference between the two line lengths. The line characteristic measuring apparatus according to claim 3, wherein: The bridge tap detection specifying means is
If there is a depression in the attenuation characteristics applied from the plurality of measuring means, it is determined that a bridge tap exists on the line to be measured, and the bridge tap length is obtained from the frequency of the depression due to the resonance that appears first. The line characteristic measuring apparatus according to claim 3. The bridge tap detection specifying means is
When a depression exists in the attenuation characteristics applied from the plurality of measuring means, it is determined that a bridge tap on the line to be measured exists, and the bridge tap length is obtained from an average value of frequency intervals of the depression due to resonance. The line characteristic measuring apparatus according to claim 3. The bridge tap detection specifying means is
4. The line characteristic measuring apparatus according to claim 3, wherein it is determined whether or not a bridge tap exists on the line to be measured by using a time domain reflection method, and the bridge tap length and the bridge tap position are obtained. The bridge tap detection specifying means is
8. The line according to claim 7, wherein when a reflected wave is detected as a reverse polarity of an incident pulse, it is determined that a bridge tap exists on the line to be measured, and the bridge tap position is obtained from the position of the reflected wave. Characteristic measuring device. The bridge tap detection specifying means is
The position of the far end of the bridge tap is obtained from the position of the second reflected wave detected as the same polarity of the incident pulse, and the bridge tap length is obtained from the difference from the bridge tap position. Eight line characteristic measuring devices. The bridge tap detection specifying means is
4. The method according to claim 3, wherein when a resonance of characteristic impedance applied from a plurality of measurement means is interference at a low impedance point, there is a possibility that a bridge tap exists on the measured line. Line characteristic measuring device. The analysis means is
A noise source estimating means for estimating a noise source by comparing a noise characteristic applied from a plurality of the measuring means and a spectrum profile of a noise source registered in advance;
2. The line characteristic measuring apparatus according to claim 1, further comprising line model drawing means for drawing a line model by using an estimated noise source. The analysis means is
Loading wire ring detection specifying means for determining the number and position of the loaded wire rings present on the line to be measured based on low frequency resonance characteristics applied from a plurality of the measuring means;
2. The line characteristic measuring apparatus according to claim 1, comprising line model drawing means for estimating and drawing a line model using the obtained number of loaded wire rings and their positions. In a line characteristic measuring device for communication lines,
Switching means for switching the output destination of the line under test;
A plurality of measuring means for measuring various line characteristics connected to a plurality of outputs of the switching means;
Control means for controlling the switching means and the plurality of measuring means;
Display means;
An apparatus for measuring line characteristics, comprising: analyzing means for estimating a line characteristic after eliminating a cause of a failure or a noise source based on various line characteristics measured by a plurality of said measuring means and drawing on said display means. The analysis means is
Specific spectrum removing means for removing a spectrum caused by a failure factor from the various line characteristics;
Arithmetic means for performing inverse FFT transform on the characteristic from which the spectrum output from the specific spectrum removing means is removed;
14. The line characteristic measuring apparatus according to claim 13, further comprising line characteristic drawing means for adding the output of the calculating means to the theoretical curve to estimate and draw the line characteristic after eliminating the failure factor. The analysis means is
Specific spectrum removing means for removing a spectrum of noise caused by a noise source from the various line characteristics;
14. The line characteristic measuring apparatus according to claim 13, further comprising line characteristic drawing means for removing a noise level at a neighboring frequency of the spectrum and estimating and drawing the line characteristic after eliminating the noise source.

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