JP3163960B2 - Propagation delay time correction method for transmission line propagation delay time measurement system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission line propagation delay time measuring technique for measuring a transmission line propagation delay time, and more specifically to a TDR (Time Domain).
The technique relates to a technique for correcting a propagation delay time measured by a Reflectmeter method.

[0002]

2. Description of the Related Art Next, a conventional transmission line propagation delay time measuring method will be described with reference to FIGS. FIG. 3 shows a configuration of a conventional propagation delay time measuring system.
FIG. 4 shows a processing flow of the measuring method in FIG. 3, and FIG. 5 shows a waveform chart in this processing.

In FIG. 3, reference numeral 8 denotes a test signal generation circuit;
Is a measurement point for detecting a waveform, 10 is a transmission line, 11 is an open end of the transmission line, 12 is a timing measurement circuit for measuring a time required for the waveform to reach an arbitrary voltage value, and 14 is an arithmetic processing of the measured value. It is an arithmetic circuit to perform. Also, 19 in FIG.
Are the voltage amplitudes 0 to V _h and the rise time T
It is a waveform of the test signal of _r . Furthermore, 20 is an open end 11
, And 21 is the waveform at the measurement point 9.

Next, the operation of the prior art will be described with reference to FIGS. A test signal 19 is supplied from the test signal generating circuit 8 to the transmission line 10, and a time T _{1 at} which the voltage of the waveform 21 at the measurement point 9 becomes V ₂ is measured in order to determine the time when the test signal 19 is applied to the transmission line 10. (S400). Next, in order to determine the time when the reflected wave from the open end 11 returns,
Voltage waveform 21 measuring points 9 seek time T ₂ to be V ₃ (S402). Further, the difference T ₂ −T ₁ between the time T ₁ and the time T ₂ is _{calculated by calculating} a round-trip propagation delay time _Trfl of the transmission line 10.
Calculated as (S404), calculates the propagation delay time T _pd to the open end 11 of the split transmission line 10 in two propagation delay time T _rfl round trip (S406).

[0005]

However, such prior art assumes an ideal case where there is no attenuation in the transmission line, and in actuality, attenuation occurs in the transmission line.
For this reason, there is a problem that the measurement error of the conventional measurement method becomes large, and a highly accurate measurement of the propagation delay time cannot be performed.

Next, to clarify this point, a case where attenuation occurs in the transmission line will be described with reference to FIG. In FIG. 6, reference numeral 22 denotes a waveform at the open end 11 when attenuation occurs due to the transmission line and the waveform becomes blunt, and numeral 23 denotes a measurement point 9 when the attenuation occurs due to the transmission line and the waveform becomes blunt. It is a waveform. As shown in FIG. 6, the round-trip propagation delay time T _rfl by blunt waveform as the open end of the waveform 22 and the measuring point waveform 23, not equal to twice the propagation delay time T _pd to the open end 11 , A measurement error T _error occurs. For example, a measurement error T _error of several tens of picoseconds occurs in a short time measurement of about nanoseconds.

The present invention relates to a propagation delay time correction method capable of accurately measuring a transmission line propagation delay time in a transmission line propagation delay time measuring system by reducing a measurement error T _error due to transmission line attenuation in the prior art. The purpose is to provide.

[0008]

SUMMARY OF THE INVENTION To achieve this object, the present invention provides a test signal 19 transmitted through a transmission line 10.
Is reflected by the open end 11, and the returned reflected wave is detected at the measurement point 9 to measure the propagation delay time of the transmission line 10. A test signal generation circuit 8 for generating a test signal for measuring the propagation delay time of the line 10 and one end connected to the test signal generation circuit 8 via a measurement point 9 for measuring the propagation delay time, A transmission line 10 having an open end, a timing measurement circuit 12 for measuring a time when the measurement point 9 reaches a predetermined voltage value, and a transmission line propagation delay time obtained by simulating the transmission line propagation delay time measurement system. And a data table 13 in which data of measurement errors are stored as correction data, and a measurement value measured by the timing measurement circuit 12. It calculates a delay time, by referring to the data table 13 and an arithmetic circuit 7 for correction of the propagation delay time.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a propagation delay time correcting method in a transmission line propagation delay time measuring system according to the present invention will be described in detail with reference to FIGS.

FIGS. 1, 2 and 6 show an embodiment of the correction method of the transmission line propagation delay time measuring method according to the present invention. FIG. 1 is a flowchart of the measurement method, and steps S100 to S112 show the processing flow of the present embodiment.

FIG. 2 shows functional blocks of the present embodiment. In FIG. 2, reference numeral 13 denotes a data table in which data for correcting the round-trip propagation delay time of the transmission line and the measurement error are stored by simulation using the same circuit model, and other functional blocks other than the arithmetic circuit 7 are shown in FIG. Is the same as That is, the arithmetic circuit 7 in the present embodiment performs the processes S106 to S112 shown in FIG.
Execute

A waveform 22 in FIG. 6 is a waveform at the open end 11 when the transmission line 10 is attenuated due to the presence of attenuation, and a waveform 23 is a waveform at the open end where the transmission line 10 is attenuated. 9 is a waveform at a measurement point 9 when a rise occurs. Others are shown in FIG.
Is the same as

In order to prepare a data table indicated by reference numeral 13 in FIG. 2, a simulation is performed in advance using a circuit model similar to that shown in FIG. 2, and data of a round-trip propagation delay time and a measurement error by a conventional measurement method are obtained. Keep it. In this simulation, the attenuation Loss of the transmission line 10 is
The rise time _Tr of the test signal 19, which is the same as the test signal used for the measurement, is set to a constant value, and the line length L of the transmission line 10 is used as a variable.

When measuring the transmission line propagation delay time, first, in order to obtain the test start time by the timing measurement circuit 12, the time T _{1 at} which the waveform 23 at the measurement point becomes the voltage V ₂ is obtained.
Is measured (S102). In addition, the timing measurement circuit 1
To determine the time that has returned the reflected wave by the reflection by the open end 11 by 2, the waveform 23 of the measurement point for measuring the time T ₂ which is a voltage V ₃ (S104).

Next, the arithmetic circuit 7 calculates the measured time T ₁
When calculating the propagation delay time T _rfl round trip of the transmission line 10 from the difference T ₂ -T ₁ time T ₂ (S106), the calculated propagation delay time T _rfl round trip was split in two, the propagation delay of the transmission line The time T _pd is derived (S108). Further, the arithmetic circuit 7 refers to the data of the round trip propagation delay time and the measurement error obtained by the simulation from the data table 13 (S110).

The data referred to at this time are the two attenuations X closest to the measured attenuation Loss of the transmission line 10.
X ₁ and XX ₈ (XX ₁ <attenuation of transmission line 10 <X
X ₈ ), the measured round-trip propagation delay time _Trfl
XX ₃ , XX ₆ , XX ₁₀ , XX
_{13 (XX 3 <T rfl <} XX 6, XX 10 <T rfl <X
And X _13), the measurement error T _error 4 pieces of data XX ₄ of, X
X _7, is XX _11, XX _14.

First, the arithmetic circuit 14 determines the attenuation amounts XX ₁ and XX from the relationship between the round-trip propagation delay time _Trfl obtained by measurement and the round-trip propagation delay time in the data table.
_The measurement error is obtained by linear interpolation for S8 (S11).
2). The calculation formulas are shown in Formula (1) and Formula (2).

[0018]

(Equation 1) Further, the arithmetic circuit 7 calculates the respective attenuation amounts XX ₁ and XX ₈
Measurement error T _{er ror} against (XX ₁₎ and T _error (XX
_{Using 8} ), a measurement error T _error1 for correction with respect to the value of the attenuation Loss of the transmission line 10 is derived by linear interpolation. The calculation formula is shown in (3).

[0019]

(Equation 2) Then, the arithmetic circuit 7 can obtain a transmission line propagation delay time with a smaller error by subtracting the correction measurement error T _error1 from the transmission line propagation delay time T _pd obtained by the measurement.

Next, a specific example of this embodiment will be described with reference to FIGS.
This will be described with reference to FIG. As shown in FIG. 7, the test signal generating circuit 8 includes a test signal generator 24, an amplifier 25 having an amplification degree of 1,
It is constituted by a resistor 26 of 50Ω. The transmission line 10 has a line length L of 2 m and an attenuation Loss of 0.4.
It is constituted by a coaxial line 27 of _{5dB / m (f o = 100MHz} ).

The timing measuring circuit 12 determines the judgment voltage value V
₂ is 0.25 V, the determination voltage value V ₃ and a comparator 28 which is set to 0.75 V. The data table 13 indicates that the line length L of the coaxial line 27 is 1.5 m, 2
m, and 2.5 m, attenuation Loss and the 0.4 dB / m and _{0.5dB / m (f o = 100MHz} ), round-trip propagation delay time due to simulation with 5ns rise time T _r of the test signal 30 T _rfl1 and measurement error T
It is a table of _error , and a part of it is shown in FIG. The arithmetic processing circuit 7 is configured by a computer 29 that inputs the detection output of the comparator 28 and the data in the data table 13.

The test signal 30 shown in FIG. 8 has a voltage amplitude of 1 V and a rise time of 5 ns. The waveform 31 is the open end 11
The waveform 32 is the waveform at the measurement point 9.

From the waveform 32 at the measurement point, the voltage value V ₂ is 0.2
5V become time T ₁ is 2.474Ns, time T ₂ in which the voltage value V ₃ becomes 0.75V is 23.575Ns, the propagation delay time T _rfl round trip T ₂ -T ₁ than 21.
101 ns. Further, from this value, the propagation delay time T _pd of the coaxial line 27 is 10.551 ns from equation (4).

T _pd = _Trfl / 2 = _21.101 / 2 = _10.551 ns (4) Next, two attenuations which are the closest to the attenuation of the coaxial line 27 of 0.45 dB / m. 0.4 dB / m and 0.5 dB /
m and the measured propagation delay time T _rfl
The data of the two values closest to the value of 21.101 ns is referred from the data table 13. First, linear interpolation is performed on the reference data in the data table 13 so that the round-trip propagation delay time _Trfl becomes 21.101 ns. Measurement error T when attenuation Loss is 0.4 dB / m
_error (0.4) is −89.0457p from the equation (5).
s.

[0025]

(Equation 3) Measurement error T when attenuation Loss is 0.5 dB / m
_error (0.5) is −111.1123 from the equation (6).
ps.

[0026]

(Equation 4) Then, using the measurement errors T _error (0.4) and T _error (0.5) obtained by the equations (2) and (3), the measurement error T _error1 for correction is _expressed by the equation (7). Is derived by linear interpolation.

[0027]

(Equation 5) By correcting the propagation delay time T _pd of the measurement value using the measurement error T _error1 for correction, the propagation delay time T _pd1 of the final correction result becomes _10.651 ns. T _pd1 = T _pd −T _error1 = 10.551 ns + 0.100079 ns = 10.651 ns In the present embodiment, the propagation delay time of the coaxial line 27 is 1
0.651 ns, and 10.651 ns is obtained as the propagation delay time after correction according to the present invention.

[0028]

According to the present invention, since the propagation delay time measurement value is linearly interpolated in consideration of the attenuation of the transmission line, the measurement error is reduced as compared with the conventional measurement method, and the propagation delay time can be accurately determined. Can measure.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an embodiment of a propagation delay time correction method in a transmission line propagation delay time measuring system according to the present invention.

FIG. 2 is a configuration diagram showing an embodiment of a transmission line propagation delay time measuring system according to the present invention.

FIG. 3 is a configuration diagram of a conventional transmission line propagation delay time measurement system.

FIG. 4 is a flowchart of a conventional transmission line propagation delay time measuring system.

FIG. 5 is a waveform diagram in an ideal case where there is no attenuation in a transmission line.

FIG. 6 is a waveform diagram showing a case where the transmission line has attenuation.

FIG. 7 is a specific configuration diagram showing an embodiment of a transmission line propagation delay time measuring system according to the present invention.

8 is a voltage waveform diagram at each point in the transmission line propagation delay time measurement system shown in FIG. 7;

FIG. 9 is a table showing contents of a data table in the transmission line propagation delay time measuring system shown in FIG. 7;

[Explanation of symbols]

 7 arithmetic circuit 8 test signal generation circuit 9 measurement point 10 transmission line 11 open end 12 timing measurement circuit 13 data table

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04L 1/20 G01R 31/28

Claims (2)

(57) [Claims] A test signal (19) transmitted through a transmission line (10) is reflected by an open end (11), and the returned reflected wave is detected at a measurement point (9), whereby the transmission line (10) is detected. The propagation delay time correction method in the transmission line propagation delay time measurement system for measuring the propagation delay time of (1) includes a test signal generation circuit (8) that generates a test signal for measuring the propagation delay time of the transmission line (10). A transmission line (10) having one end connected to the test signal generation circuit (8) via the measurement point (9) for measuring the propagation delay time, and having the other end open; and a measurement point (9). A timing measurement circuit (12) for measuring a time when the signal reaches a predetermined voltage value, and data of a transmission line propagation delay time and a measurement error obtained by simulating the transmission line propagation delay time measurement system are stored as correction data. Data table (1
3) and an arithmetic circuit (7) that calculates the propagation delay time from the measurement value measured by the timing measurement circuit (12) and performs the propagation delay time correction process with reference to the data table (13). A method for correcting a propagation delay time in a transmission line propagation delay time measuring system, characterized in that: 2. The propagation delay time correction method according to claim 1, wherein the arithmetic circuit includes data of two attenuation amounts close to the attenuation amount of the transmission line, and the measured transmission line. The data of the two propagation delay times close to the propagation delay time are referred to from the data table (13), and the transmission line (10) calculated from the measurement value measured by the timing measurement circuit (12) from these data is used. Correction data is linearly interpolated so as to be the same as the propagation delay time, and the measurement error at this time is obtained.
(10) A transmission error characterized by performing a correction process on the propagation delay time of the calculated measurement value by deriving a measurement error with respect to the attenuation amount by linear interpolation, and correcting the propagation delay time of the transmission line (10). A propagation delay time correction method in a line propagation delay time measurement system.