JPH1010176A - Method and system for evaluating receiving characteristics - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the measuring time without lowering the measurement accuracy. SOLUTION: A measurement signal 1a of reference level is inputted to an object and a receiving side error rate measuring unit 2 measures the error rates for both logical levels '1' and '0' indicative of the 'eye pattern' of an output signal 1b depending on threshold voltages designated on threshold voltage tables 8, 9 and the error rates thus measured are recorded at data storing sections 14, 15. After finishing measurements predetermined number of times, approximating sections 19, 20 perform linear approximation on the data recorded at the data storing sections 14, 15. Subsequently, a variable calculating section 21 calculates a mean space level, a mean mark level, a space noise standard deviation and a mark noise standard deviation based on the approximation results 19a, 20a received from the approximating sections 19, 20 and a Q value calculating section 22 calculates a Q value based on the calculation results received from the variable calcuiating section 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for evaluating reception characteristics, and more particularly to a method and an apparatus for evaluating reception characteristics of a device under test (for example, a submarine repeater) requiring high reliability.

In order to evaluate the receiving characteristics of a submarine repeater or the like, it is necessary to perform error rate measurement over a wide range from a high error rate to a low error rate. Further, in order to guarantee the reliability, it is necessary to measure an extremely low error rate (for example, about 10 ⁻¹³ ), and the measurement requires a long time. For this reason,
An evaluation method using a Q value has attracted attention as a method for evaluating the reception characteristics in a short measurement time, and there is a demand for a device.

[0003]

2. Description of the Related Art As a conventional reception characteristic evaluation apparatus, for example, Japanese Patent Application Laid-Open No. 62-212584 is known.

This conventional reception characteristic evaluation device changes the noise level added to a carrier stepwise, calculates an error rate characteristic by one measurement at each carrier-to-noise (C / N) point, and performs reception. The purpose of this is to evaluate the characteristics and to eliminate the need for manual labor and to improve the efficiency of measurement.

Next, this conventional reception characteristic evaluation apparatus will be described with reference to the drawings. FIG. 2 is a block diagram showing an embodiment of a conventional reception characteristic evaluation device.

In this case, the transmission side error rate measuring device 25 is used as a simple pulse signal generator, and the pulse signal
It is applied to the CM modulator 26. Noise is added to the modulated signal 26a of the PCM modulator 26 by the noise adder 27, and the modulated wave 27a to which the noise is added is applied to the PCM demodulator 28, which is the device under test, and the number of errors in the output 28a of the PCM demodulator 28 Alternatively, the error rate is measured by the error rate measuring device 29 on the receiving side.
Measure with Output value 29 from reception side error rate measuring device 29
The computer 30 that has received the control signal 30a
a is sent to the noise adder 27 to change the noise level to be added. Then, the computer 30 calculates, for each C / N point, an output value 29a corresponding to the number of errors or the error rate output from the receiving-side error rate measuring device 29 as an approximate value indicating a constant straight line. Calculate the characteristics.

[0007]

When the error rate straight line (or curve) for evaluating the reception characteristic is created, the conventional reception characteristic evaluation apparatus described above changes the noise level applied to the device under test and changes each value. The error rate is measured and created, but at multiple points until the required error rate is met,
Measurement takes time. In the case of a device under test that requires high reliability, as the error rate increases, more data is required to guarantee the error rate. There is a problem that it affects the entire measurement time.

An object of the present invention is to provide a receiving characteristic evaluation method and apparatus capable of shortening the measurement time without lowering the measurement accuracy.

[0009]

A receiving characteristic evaluation method according to the present invention is a receiving characteristic evaluating method for evaluating a receiving characteristic of a device under test for relaying a digital data signal. And an error rate for each of two sets of a plurality of threshold potentials each including a high potential and a low potential of a predicted logical value of the output of the device under test as a median of the threshold potentials. Measure and calculate a coefficient to display a straight line by linear approximation using the error rate for each threshold potential of the high potential and the low potential,
An average potential and a noise standard deviation of each of the high potential and the low potential are obtained using the two sets of coefficients, and a Q value is calculated from the average potential and the noise standard deviation.

A receiving characteristic evaluation apparatus according to the present invention comprises: a transmitter-side error rate measuring device for inputting a measurement signal to a device-under-test; And a receiving-side error-rate measuring device for inputting a synchronization signal from the transmitting-side error-rate measuring device, and a number of measurements in which the number of changes of a threshold voltage serving as a reference of the error-rate measurement of the receiving-side error-rate measuring device is stored in advance. A storage unit, a region number storage unit that previously stores “2” as the number of measurement regions to be measured by finely changing the threshold voltage, a first counter that counts the number indicating the measurement region of the threshold voltage, A second counter that counts the number of times the threshold voltage has been finely changed, a counter erasing unit that erases the value of the second counter when the value of the first counter increases, and a value of the first counter. A first threshold voltage table that stores the threshold voltage measured in the case of “1” for the number of changes stored in the measurement count storage unit, and a threshold voltage measured in the case where the value of the second counter is “2”. A second threshold voltage table stored for the number of changes stored in the number-of-measurements storage unit, and a value of the first counter and a value of the second counter are input for each error rate measurement operation, and the values corresponding to these two values are input. A threshold voltage reading unit that reads a determined threshold voltage value from one of the first threshold voltage table and the second threshold voltage table; and a value read by the threshold voltage reading unit as a threshold voltage change value. A threshold voltage changing unit for instructing an error rate measuring device; and An error rate measurement instructing unit that instructs an error rate measurement to a rate measuring device, and an error rate measurement result receiving unit that receives the error rate measured from the receiving side error rate measuring device after the error rate measurement instructing unit has completed the instruction. A first data storage unit that stores a threshold voltage vs. error rate when the value of the first counter is “1”; and a second data storage unit that stores a threshold voltage vs. error rate when the value of the first counter is “2”. (Ii) writing the value specified by the threshold voltage changing unit and the reception result of the error rate measurement result receiving unit to the first data storing unit when the value of the first counter is “1”; A data writing unit that writes data to the second data storage unit when the value of the first counter is “2”; and a value of the second counter and the number of measurement times storage unit after writing of the data writing unit. Compare the value with the second A first comparison unit that returns control to the second counter when the value of the counter is less than the value indicated by the measurement times storage unit, and the value of the first counter when the comparison result of the first comparison unit is the same. A second comparison unit that compares the value of the area number storage unit and returns control to the first counter when the value of the first counter does not match the value indicated by the area number storage unit; A first approximation unit that linearly approximates the data of the first data storage unit when the comparison result is a match, and a second approximation unit that linearly approximates the data of the second data storage unit after the first approximation unit finishes the approximation. A variable calculation unit that calculates an average space level, an average mark level, a space noise standard deviation, and a mark noise standard deviation from each coefficient of the approximation formula calculated by the first approximation unit and the second approximation unit; Using the calculation result of the calculation unit A configuration including a Q value calculation unit for calculating a value.

[0011] A receiving characteristic evaluation method and apparatus according to the present invention include:
The device under test may be an optical submarine repeater.

[Operation] In the method and the apparatus for evaluating reception characteristics of the present invention, a digital data signal of a reference level is input to a device under test, and a logical value "1" indicating an "eye pattern" of the digital data signal to be output and a logic value "1" are output. Each of the logical values “0” is detected at a plurality of predetermined threshold voltages in synchronization with the input signal, and the error rate at this time is recorded. 100% error rate if the characteristics of the device under test are stable
And the threshold voltage indicating the error rate of 0% are displayed very close. Normally, a plurality of threshold voltages are set between a threshold voltage indicating an error rate of 100% and an error rate of 0%, and an error rate between the error rate of 100% and the error rate of 0% is calculated. In this case, as data used for calculating the error rate for each threshold voltage, even data measured for each measurement potential without taking as much time as conventional measurement is sufficient if it can calculate a linear approximation. By calculating an average space level, an average mark level, a space noise standard deviation, and a mark noise standard deviation from each coefficient of, and calculating a Q value using the calculation result,
Even in a short measurement, the accuracy of the reception characteristic evaluation can be improved.

[0013]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

The receiving characteristic evaluation apparatus of the present invention comprises: a transmitting side error rate measuring device 1 for inputting a measurement signal 1a to a device under test;
An error rate measuring device 2 on the receiving side, which receives the output signal 1b of the device under test inputted from the measuring signal 1a of the measuring device 1 on the transmitting side and a synchronizing signal 1c from the measuring device 1 on the transmitting side, and measures the error rate on the receiving side The number-of-measures storage unit 3 in which the number of changes of the threshold voltage serving as a reference of the error rate measurement of the measuring device 2 is stored in advance, and “2” is stored in advance as the number of measurement areas to be measured by finely changing the threshold voltage. The number of areas to be stored, a counter 5 for counting the number indicating the threshold voltage measurement area, a counter 6 for counting the number of times the threshold voltage has been finely changed, and the value of the counter 5 has increased by “1”. Counter erasing section 7 for erasing the value of counter 6 when
And a threshold voltage table 8 for storing the threshold voltage measured when the value of the counter 5 is "1" for the number of changes stored in the number-of-measures storage unit 3, and the value of the counter 5 being "2".
The threshold voltage to be measured in the case of
Threshold voltage table 9 for the number of changes stored in Table 9
And the value of the counter 5 and the value of the counter 6 are input for each error rate measurement operation, and the threshold voltage value determined corresponding to these two values is read out from one of the threshold voltage table 8 and the threshold voltage table 9. A threshold voltage reading unit 10 and a threshold voltage changing unit 11 for instructing the error rate measuring device 2 on the reception side with a value read by the threshold voltage reading unit 10 as a changed value of the threshold voltage.
And an error rate measurement instructing unit 12 in which the threshold voltage changing unit 11 instructs the error rate measurement unit 2 on the receiving side after the instruction is completed, and an error rate measurement instructing unit 12 in which the error rate measurement instructing unit 12 is instructed after the instruction is completed. An error rate measurement result receiving unit 13 for receiving an error rate measured from the data storage unit 14 for storing a threshold voltage versus an error rate when the value of the counter 5 is “1”;
When the value of the counter 5 is “2”, the data storage unit 15 stores the threshold voltage versus the error rate, and the value specified by the threshold voltage changing unit 11 and the reception result of the error rate measurement result receiving unit 13 are stored in the counter 5 When the value of the counter 5 is "1", the data writing unit 16 writes the data into the data storage unit 15, and when the value of the counter 5 is "2", the data writing unit 16 writes the data into the data storage unit 15; 6 and the value of the number-of-measurements storage unit 3, and when the value of the counter 6 is smaller than the value indicated by the number-of-measures storage unit 3, the comparison unit 17 returns control to the counter 6, and the comparison result of the comparison unit 17 A comparison unit 18 that compares the value of the counter 5 with the value of the number-of-regions storage unit 4 when the values match, and returns control to the counter 5 when the value of the counter 5 does not match the value indicated by the number-of-regions storage unit 4; The comparison result of the comparison unit 18 is If it is, an approximation unit 19 that approximates the data of the data storage unit 14 with a straight line, an approximation unit 20 that approximates the data of the data storage unit 15 with a straight line after the approximation is completed, and an approximation unit 19 and an approximation unit 20 that calculate A variable calculator 21 that calculates an average space level, an average mark level, a space noise standard deviation, and a mark noise standard deviation from each coefficient of the approximate expression thus calculated, and calculates a Q value using the calculation result of the variable calculator 21. And a Q value calculation unit 22.

Next, the operation will be described.

FIG. 3 is an explanatory diagram showing an example of an eye pattern of an output signal of the transmission side error rate measuring device and an output signal of the device under test.

The transmission-side error rate measuring device 1 continuously outputs the measurement signal 1a and inputs it to the device under test. The receiving side error rate measuring device 2 receives the output signal 1b from the device under test and measures the error rate. The transmission-side error rate measurement device 1 and the reception-side error rate measurement device 2 are synchronized by a synchronization signal 1c.

FIG. 4 is an explanatory diagram for explaining the relationship between the eye pattern and the location where the threshold voltage is initially set. In the following description, the names and reference numerals of FIG. 1 are mainly used, and FIGS. 3 and 4 are appropriately referred to.

Prior to the characteristic evaluation, the threshold voltage at which the error rate at the mark level (data 1 level) 23 shown in FIG. Similarly for the space level (data 0 level) 24, the threshold voltage is written in the same number threshold voltage table 9. The number of voltages written in the threshold voltage tables 8 and 9 is also written in the number-of-measures storage unit 3. At the same time, "2" is stored in the number-of-regions storage unit 4.
Is written.

When the characteristic evaluation is started, first, the counter 5
Is increased by “1” (counter value 1). Next, after the counter 6 is cleared by the counter erasing section 7, the counter 6 is incremented by "1" again (counter value 1). Subsequently, the threshold voltage reading unit 10 refers to the value of the counter 5 and is written in advance from the threshold voltage table 8 when the counter value is “1” and from the threshold voltage table 9 when the counter value is “2”. The threshold voltage value 10a stored at the address indicated by the counter 6 is read. The threshold voltage value 10a read by the threshold voltage reading unit 10
Is set as the measuring device control signal 2a in the receiving side error rate measuring device 2 by the threshold voltage changing unit 11. After completing the settings,
The error rate measurement instructing unit 12 similarly instructs the reception side error rate measurement device 2 to perform the error rate measurement as the measurement device control signal 2a. After the instruction, the error rate measurement result receiving unit 13 receives the measurement result transmitted by the reception side error rate measurement device 2 through the measurement device control signal 2a. The received result is stored in the data
With reference to the value (5a), when the counter value is “1”, the data storage unit 14 stores the counter value, and when the counter value is “2”, the data storage unit 15 stores the threshold voltage (10b) versus the error rate in the data 16a. Write as After writing, the value (6a) of the counter 6 is compared with the value of the number-of-measurements storage unit 3, and when the value of the counter 6 (6a) <the value of the number-of-measures storage unit 3 is satisfied,
The value of the counter 6 is increased by "1", and the same is repeated thereafter.
When the value of the counter 6 (6a) = the value of the number-of-measurements storage unit 3, the value of the counter 5 is compared with the value of the number-of-regions storage unit 4, and
When the value of (5a) <the value of the number-of-regions storage unit 4, the counter 5 is incremented by "1", and the same is repeated. When the value of the counter 5 (5a) = the value of the number-of-regions storage unit 4, the approximation unit 19 linearly approximates the data 14a of the data storage unit 14 (y = a1x + b1), and calculates coefficients a1 and b1. Similarly, the approximation unit 20 performs linear approximation (y = a2x + b2) of the data 15a of the data storage unit 15 to obtain a coefficient a2
b2 is calculated. Subsequently, the variable calculation unit 21 calculates the average space level μ0, the average mark level μ1, the space noise standard deviation σ0, and the mark noise standard deviation σ1 using the approximation results 19a and 20a including the respective coefficients. Using the result, a Q value (Q value: SN (signal / noise ratio) of the receiving unit in units of voltage or current) is obtained in the Q value calculation unit 22.
The Q value calculation method in this case is based on the following equation. Q [dB] = 20 × log ｛| μ1-μ0 | / (σ1-σ
0)｝ Note that the number of times the threshold voltage is measured when the value of the counter 5 is “1” and the number of measurements when the value of the counter 5 is “2” are stored in the number-of-measures storage unit 3. However, it is also possible to separately increase the number-of-measurements storage unit and perform measurement as different numbers.

[0022]

As described above, according to the present invention, a digital data signal is inputted to a device under test, and two values of a high potential and a low potential of a predicted logical value of an output of the device under test are set as threshold values. The error rate is measured for each of two sets of threshold potentials, each of which is included as the median of the potential, and a straight line is displayed using the error rates for each of the high potential and the low potential for each threshold potential. The coefficient to be calculated is calculated, the average potential and the noise standard deviation of each of the high potential and the low potential are obtained using the two sets of coefficients, and the Q value is calculated from the average potential and the noise standard deviation. There is an effect that the measurement time can be reduced without lowering the accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram illustrating an embodiment of a conventional reception characteristic evaluation device.

FIG. 3 is an explanatory diagram showing an example of an eye pattern of an output signal of a transmission-side error rate measuring device and an output signal of a device under test.

FIG. 4 is an explanatory diagram for explaining a relationship between an eye pattern and a threshold voltage initial setting portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmission side error rate measuring device 1a Measurement signal 1b Output signal 1c Synchronization signal 2 Receiving side error rate measurement device 2a Measurement device control signal 3 Measurement frequency storage unit 4 Area storage unit 5, 6 Counter 5a Counter 5 value 6a Counter 6 Value 7 Counter erasing section 8, 9 Threshold voltage table 10 Threshold voltage reading section 10a, 10b Threshold voltage value 11 Threshold voltage changing section 12 Error rate measurement instruction section 13 Error rate measurement result receiving section 14, 15 Data storage section 14a, 15a , 16a Data 16 Data writing unit 17, 18 Comparison unit 19, 20 Approximation unit 19a, 20a Approximation result 21 Variable calculation unit 22 Q value calculation unit 23 Mark level position 24 Space level position

Claims (4)

[Claims] In a receiving characteristic evaluation method for evaluating a receiving characteristic of a device under test that relays a digital data signal, the digital data signal is input to the device under test, and an output of the device under test is predicted. The error rate is measured for each of a plurality of sets of threshold potentials each including a high value and a low value of a logical value as a median of the threshold value, and the thresholds of the high and low potentials are measured. A coefficient for displaying a straight line is calculated by linear approximation using the error rate for the value potential, and an average potential and a noise standard deviation of each of the high potential and the low potential are calculated using the two sets of coefficients. A receiving characteristic evaluation method, wherein a Q value is calculated from a potential and a noise standard deviation. 2. A transmission side error rate measuring device for inputting a measurement signal to the device under test, an output signal of the device under test inputting a measurement signal of the transmission side error rate measuring device, and a transmission side error rate measuring device A receiving-side error rate measuring device for inputting a synchronization signal from the receiving side; a measuring frequency storage unit for storing in advance a changing frequency of a threshold voltage serving as a reference of the error rate measurement of the receiving-side error rate measuring device; The number-of-regions storage unit that previously stores “2” as the number of measurement regions to be finely changed and measured, the first counter that counts the number indicating the measurement region of the threshold voltage, and the threshold voltage is finely changed A second counter for counting the number of changes, a counter erasing unit for erasing the value of the second counter when the value of the first counter increases, and a thread for measuring when the value of the first counter is "1". A first threshold voltage table that stores the threshold voltage for the number of changes stored in the number-of-measures storage unit, and a change that stores the threshold voltage measured when the value of the second counter is “2” in the number-of-measures storage unit A second threshold voltage table to be stored for the number of times, and a value of the first counter and a value of the second counter for each error rate measurement operation, and a threshold voltage value determined corresponding to these two values are input to the second threshold voltage table. A threshold voltage reading unit for reading from one of the threshold voltage table and the second threshold voltage table, and a threshold for instructing the reception side error rate measuring device the value read by the threshold voltage reading unit as a changed value of the threshold voltage. A voltage changing unit and the threshold voltage changing unit instructs the receiving side error rate measuring device to measure an error rate after the instruction is completed. An error rate measurement instructing unit, an error rate measurement result receiving unit that receives the error rate measured from the receiving side error rate measuring device after the error rate measurement instructing unit completes the instruction, and a value of the first counter is “1”. A first data storage unit for storing a threshold voltage versus an error rate when the value of the first counter is "2"; a second data storage unit for storing a threshold voltage versus the error rate when the value of the first counter is "2"; When the value of the first counter is "1", the value instructed by the changing unit and the reception result of the error rate measurement result receiving unit are written to the first data storage unit, and the value of the first counter is similarly set to "1". 2 ", a data writing unit for writing data to the second data storage unit, and comparing the value of the second counter with the value of the measurement count storage unit after writing by the data writing unit. Is the number of measurements A first comparison unit that returns control to the second counter when the value is less than the value indicated by the storage unit, and a value of the first counter and a value of the region number storage unit when the comparison result of the first comparison unit matches. When the value of the first counter does not match the value indicated by the number-of-regions storage unit, the second comparison unit that returns control to the first counter and the comparison result of the second comparison unit match. A first approximation unit that linearly approximates the data of the first data storage unit, a second approximation unit that linearly approximates the data of the second data storage unit after the first approximation is completed, and the first approximation unit And a variable calculation unit that calculates an average space level, an average mark level, a space noise standard deviation, and a mark noise standard deviation from each coefficient of the approximation formula calculated by the second approximation unit, and a calculation result of the variable calculation unit. And a Q value calculation unit for calculating the Q value A receiving characteristic evaluation device characterized by including: 3. The method according to claim 1, wherein the device under test is an optical submarine repeater. 4. The receiving characteristic evaluation device according to claim 2, wherein the device under test is an optical submarine repeater.