Jitter tolerance measuring device and jitter tolerance measuring method

Abstract

The present invention provides a jitter tolerance measuring device and a jitter tolerance measuring method that can automatically calculate the measurement time required to obtain a desired reliability level and perform error measurements to obtain the jitter tolerance of an object under test over the calculated measurement time. [Solution] The jitter tolerance measuring device includes an error measurement unit 14 that measures the number of errors and error rate of the output signal of the DUT200, which receives a pattern signal synchronized with a jitter clock phase-modulated by a jitter modulation signal, over a predetermined measurement time; a jitter tolerance measuring unit 16 that changes the jitter amplitude and jitter frequency of the jitter modulation signal and estimates the maximum jitter amplitude at which the number of errors or error rate measured by the error measurement unit 14 is less than or equal to a predetermined tolerance value as the jitter tolerance of the DUT200 for each jitter frequency; a measurement time setting unit 20 that calculates the measurement time and sets it in the error measurement unit 14; and a display unit 32 that displays a setting screen 40 for setting the measurement conditions for jitter tolerance.

Description

[Technical Field]

[0001] The present invention relates to a jitter tolerance measuring device and a jitter tolerance measuring method for measuring the jitter tolerance of an object under test. [Background technology]

[0002] For example, in communication standards such as USB® (Universal Serial Bus) and PCIe® (Peripheral Component Interconnect Express), jitter tolerance tests are conducted to determine whether the receiving section of the device under test (DUT) has the desired jitter tolerance (see, for example, Patent Documents 1 and 2).

[0003] Figure 8 shows the configuration of a conventional jitter tolerance measuring device 50 for performing jitter tolerance testing. This jitter tolerance measuring device 50 consists of a jitter generator 51 that outputs a jitter clock phase-modulated with a jitter modulation signal whose jitter amplitude and jitter frequency are variable, a pattern signal generator 52 that outputs a pattern signal synchronized with the jitter clock output from the jitter generator 51 to the DUT 55, and an error measuring device 53 that measures the error of the output signal of the DUT 55 relative to the pattern signal.

[0004] The jitter tolerance measuring device 50 configured in this way changes the jitter amplitude of the jitter modulated signal and measures the maximum jitter amplitude at which the number of errors or error rate measured by the error measuring device 53 is less than or equal to a predetermined tolerance value, as the jitter tolerance of the DUT 55.

[0005] Here, the lower limit of the jitter tolerance required for DUT55 is given as a jitter mask as shown in Figure 9.

[0006] Here, the confidence level (CL) of the number of errors or error rate of the output signal when jitter tolerance is achieved is defined by the following equation (1).

[0007]

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[0008] In equation (1), N: Bitrate [bit / s] × Measurement time [s] (Number of bits measured) BER S :Target BER (Bit Error Rate) E: Target number of errors That is the case.

[0009] The measurement time required to achieve a desired reliability level against a predefined target BER varies depending on the desired reliability level and bit rate. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 08-050156 [Patent Document 2] Patent No. 4376064 [Overview of the project] [Problems that the invention aims to solve]

[0011] However, conventional measuring devices, such as those disclosed in Patent Documents 1 and 2, could not automatically evaluate how long the measurement time needed to be in order to achieve the desired reliability level.

[0012] Therefore, conventionally, when conducting jitter tolerance tests, users had to perform cumbersome tasks such as setting the desired reliability level and calculating the measurement time required to achieve that level.

[0013] The present invention has been made to solve the above-mentioned conventional problems, and aims to provide a jitter tolerance measuring device and a jitter tolerance measuring method that can automatically calculate a measurement time that can obtain a desired reliability level and perform error measurements to obtain the jitter tolerance of an object under test over the calculated measurement time. [Means for solving the problem]

[0014] To solve the above problems, the jitter tolerance measuring device according to the present invention includes: a jitter modulation signal output unit (11) that outputs a jitter modulation signal with variable jitter amplitude and jitter frequency; a jitter clock output unit (12) that receives the jitter modulation signal from the jitter modulation signal output unit and outputs a phase-modulated jitter clock according to the jitter amplitude and jitter frequency; a pattern signal generation unit (13) that outputs a pattern signal synchronized with the jitter clock to the object under test; an error measurement unit (14) that measures the number of errors and error rate of the output signal of the object under test that receives the pattern signal over a predetermined measurement time; and a jitter tolerance measuring device that changes the jitter amplitude and jitter frequency of the jitter modulation signal output by the jitter modulation signal output unit and estimates the maximum jitter amplitude at which the number of errors or error rate measured by the error measurement unit is less than or equal to a predetermined allowable value as the jitter tolerance of the object under test for each jitter frequency. The system includes a force measuring unit (16), a measurement time setting unit (20) that calculates the measurement time of the output signal and sets the calculated measurement time to the error measuring unit, and a display unit (32) that displays a setting screen (40) for setting the measurement conditions for the jitter tolerance. The setting screen includes a target reliability level input unit (44) for inputting an acceptable value for the reliability level, a target error rate input unit (45a, 45b) for inputting an acceptable value for the error rate of the output signal, a target error count input unit (46) for inputting an acceptable value for the number of errors during the measurement time of the output signal, and a measurement time display unit (43) for displaying the measurement time of the output signal. The measurement time setting unit is configured to calculate the measurement time that gives the acceptable reliability level based on the data rate of the output signal, the acceptable reliability level, the acceptable error rate, and the acceptable number of errors input to the setting screen.

[0015] With this configuration, the jitter tolerance measuring device according to the present invention can automatically calculate a measurement time that can obtain an acceptable value for a desired reliability level, and perform error measurements to obtain the jitter tolerance of the object under test over the calculated measurement time.

[0016] In other words, the jitter tolerance measuring device according to the present invention allows the user to easily calculate the measurement time and quickly start jitter tolerance measurement by setting a desired tolerance value for the reliability level on the settings screen.

[0017] Furthermore, the jitter tolerance measuring device according to the present invention has a measurement time setting unit that sets the average value x of the variables min_x and max_x. a An average value calculation unit (21) that calculates the average value x a A provisional reliability level calculation unit (22) calculates a provisional reliability level CLx by substituting the value into x in the following equation (2), and if the provisional reliability level CLx is less than or equal to the allowable value of the reliability level, the variable min_x is set to the average value x a Substitute the value and if the provisional reliability level CLx is greater than the tolerance value of the reliability level, then set the variable max_x to the mean value x a The measurement time setting unit includes an upper and lower limit update unit (23) which substitutes the latest variables min_x and max_x, and the measurement time setting unit repeats the processing of the average value calculation unit, the provisional reliability level calculation unit, and the upper and lower limit update unit, and the average value x calculated by the average value calculation unit a When the change in the value of converges to a predetermined range, the converged average value x a The configuration may further include a measurement time calculation unit (28) that calculates the measurement time by dividing the result by the product of the data rate and the allowable value of the error rate.

number

[0018] With this configuration, the jitter tolerance measuring device according to the present invention measures the average value x in error measurement of the output signal. a By performing a filtering process, it is possible to calculate a measurement time that yields an acceptable value for the desired reliability level without making the user aware that a measurement time calculation process is taking place.

[0019] Furthermore, the jitter tolerance measuring device according to the present invention uses the average value x calculated by the average value calculation unit.a includes a rounding error, and when the significant digits of the average value x a converge to a certain value, the measurement time may be calculated as a value obtained by dividing the converged average value x a by the product of the data rate and the allowable value of the error rate.

[0020] With this configuration, the jitter tolerance measurement device according to the present invention uses the convergence due to the rounding error as the end determination condition for the narrowing-down process of the average value x a , so it is possible to save the labor for the user to consider the range considered as the value of the average value x a and the number of times of repeating the process every time various measurement conditions are changed on the setting screen.

[0021] Also, the jitter tolerance measurement device according to the present invention may be configured such that the average value x a is data of double-precision floating-point numbers, and the significant digits are the mantissa part of the double-precision floating-point numbers.

[0022] With this configuration, when the numerical types of the variable min_x, the variable max_x, and the average value x a are of the double type, the measurement time can be calculated using the average value x a with about 14 significant digits in decimal conversion.

[0023] Furthermore, the jitter tolerance measurement method according to the present invention includes a jitter modulation signal output unit (11) that outputs a jitter modulation signal with variable jitter amplitude and jitter frequency, a jitter clock output unit (12) that receives the jitter modulation signal from the jitter modulation signal output unit and outputs a phase-modulated jitter clock according to the jitter amplitude and jitter frequency, a pattern signal generation unit (13) that outputs a pattern signal synchronized with the jitter clock to the object under test, and the number of errors and error rate of the output signal of the object under test that receives the pattern signal over a predetermined measurement period. A jitter tolerance measurement method using a jitter tolerance measuring device (1) comprising: an error measurement unit (14) that measures; and a jitter tolerance measuring unit (16) that changes the jitter amplitude and jitter frequency of the jitter modulated signal output by the jitter modulated signal output unit, and estimates the maximum jitter amplitude for which the number of errors or error rate measured by the error measurement unit is less than or equal to a predetermined tolerance value, as the jitter tolerance of the object under test for each jitter frequency, wherein a setting screen (40) for setting the measurement conditions for the jitter tolerance is displayed on a display unit (32). A setting screen display step (S21), an input step (S22) for inputting the tolerance value of the reliability level, the tolerance value of the error rate, and the tolerance value of the number of errors into the setting screen, a measurement time calculation step (S24) for calculating the measurement time that gives the tolerance value of the reliability level based on the data rate of the output signal and the tolerance value of the reliability level, the tolerance value of the error rate, and the tolerance value of the number of errors input into the setting screen, and a measurement time display step (S25) for displaying the measurement time calculated in the measurement time calculation step, The setting screen includes a measurement time setting step (S26) in which the measurement time calculated in the measurement time calculation step is set in the error measurement unit, and the setting screen is configured to include a target reliability level input unit (44) for inputting an acceptable value for the reliability level, a target error rate input unit (45a, 45b) for inputting an acceptable value for the error rate of the output signal, a target error count input unit (46) for inputting an acceptable value for the number of errors during the measurement time of the output signal, and a measurement time display unit (43) for displaying the measurement time of the output signal. [Effects of the Invention]

[0024] The present invention provides a jitter tolerance measuring device and a jitter tolerance measuring method that can automatically calculate a measurement time that will yield a desired reliability level and perform error measurements to obtain the jitter tolerance of an object under test over the calculated measurement time. [Brief explanation of the drawing]

[0025] [Figure 1] This is a block diagram showing the configuration of a jitter tolerance measuring device according to an embodiment of the present invention. [Figure 2] This is a block diagram showing the configuration of the measurement time setting unit included in a jitter tolerance measuring device according to an embodiment of the present invention. [Figure 3] This is an explanatory diagram illustrating the operation of the measurement time setting unit in a jitter tolerance measuring device according to an embodiment of the present invention. [Figure 4] This table shows how each value changes when the numeric type is of type double. [Figure 5] This graph shows the changes in each value when the numerical type is double. [Figure 6] This is an example of a settings screen for a jitter tolerance measuring device according to an embodiment of the present invention. [Figure 7] This flowchart shows the process of a jitter tolerance measurement method using a jitter tolerance measuring device according to an embodiment of the present invention. [Figure 8] This is a block diagram showing the configuration of a conventional jitter tolerance measuring device. [Figure 9] This is a diagram illustrating an example of a jitter mask. [Modes for carrying out the invention]

[0026] Hereinafter, embodiments of the jitter tolerance measuring device and jitter tolerance measuring method according to the present invention will be described with reference to the drawings.

[0027] As shown in Figure 1, the jitter tolerance measuring device 1 according to an embodiment of the present invention measures the jitter tolerance of a DUT200 and comprises a jitter generation unit 10, a pattern signal generation unit 13, an error measurement unit 14, a control unit 15, a data storage unit 30, an operation unit 31, and a display unit 32.

[0028] Examples of standards supported by the DUT200 include PCIe Gen1-6, USB® (Universal Serial Bus) 3.0-4, CEI (Common Electrical Interface), IEEE 802.3, InfiniBand HDR, and Fibre Channel.

[0029] The jitter generation unit 10 includes a jitter modulation signal output unit 11 and a jitter clock output unit 12.

[0030] The jitter modulation signal output unit 11 outputs a jitter modulation signal with variable jitter amplitude and jitter frequency. The jitter modulation signal is, for example, a periodic jitter such as sinusoidal jitter.

[0031] The jitter clock output unit 12 receives a jitter modulated signal from the jitter modulated signal output unit 11 and outputs a phase-modulated jitter clock according to the jitter amplitude and jitter frequency of the jitter modulated signal.

[0032] The data storage unit 30 is composed of memory such as RAM (Random Access Memory). The data storage unit 30 stores known pattern signal data that is input to the DUT200 from the pattern signal generation unit 13, which will be described later. For example, it stores bit sequence data (data consisting of a sequence of bits consisting of 0s or 1s) of NRZ (Non Return to Zero) type signals (hereinafter also simply referred to as "NRZ signals") and symbol sequence data (data consisting of a sequence of symbols consisting of 0s, 1s, 2s, or 3s) of PAM4 (Pulse Amplitude Modulation 4) type signals (hereinafter also simply referred to as "PAM4 signals").

[0033] Furthermore, the data storage unit 30 may also store the bit sequence data of the MSB (Most Significant Bit) and LSB (Least Significant Bit) of the PAM4 signal input to the DUT200. The symbol sequence data of the PAM4 signal, the bit sequence data of the MSB and LSB, and the bit sequence data of the NRZ signal stored in the data storage unit 30 also serve as reference data for comparison by the error measurement unit 14, which will be described later, with the output signal of the DUT200.

[0034] The pattern signal generation unit 13 generates a pattern signal consisting of data of known patterns input from the data storage unit 30, synchronized with the jitter clock from the jitter clock output unit 12.

[0035] The pattern signal generation unit 13 then outputs the generated pattern signal to the DUT 200 as a test signal. At this time, the DUT 200 folds back the pattern signal output from the pattern signal generation unit 13 and uses it as the output signal to the error measurement unit 14.

[0036] The error measurement unit 14 measures the number of errors and the error rate of the output signal of the DUT200, which receives a pattern signal from the pattern signal generation unit 13, for each combination of jitter amplitude and jitter frequency of the jitter modulated signal over a predetermined measurement time.

[0037] The error measurement unit 14 calculates the error rate of the output signal of the DUT200 by sequentially comparing the bit sequence data or symbol sequence data contained in the output signal of the DUT200 with reference data stored in the data storage unit 30.

[0038] Furthermore, the jitter tolerance of the error measurement unit 14 itself is sufficiently higher than the jitter tolerance measurement range of the DUT200.

[0039] The error measurement unit 14 counts the number of errors in the output signal of the DUT200 over a measurement period set by the measurement time setting unit 20, which will be described later. Furthermore, the error measurement unit 14 calculates the error rate of the output signal of the DUT200 by dividing the counted number of errors by the number of measurement data points of the output signal over the above measurement period.

[0040] The control unit 15 is composed of a control device such as a computer, which includes, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an FPGA (Field Programmable Gate Array), ROM (Read Only Memory), RAM, and an HDD (Hard Disk Drive).

[0041] The control unit 15 provides overall control over the jitter generation unit 10, the pattern signal generation unit 13, the error measurement unit 14, the data storage unit 30, the operation unit 31, and the display unit 32. Furthermore, for example, the control unit 15 configures the jitter tolerance measurement unit 16 and the measurement time setting unit 20 through software by executing a predetermined program using a CPU or GPU.

[0042] The jitter tolerance measurement unit 16 changes the jitter amplitude and jitter frequency of the jitter modulated signal output by the jitter modulated signal output unit 11, and estimates the maximum jitter amplitude at which the number of errors or error rate measured by the error measurement unit 14 is below a predetermined tolerance value, as the jitter tolerance of the DUT200 for each jitter frequency.

[0043] The measurement time setting unit 20 calculates the measurement time of the output signal of the DUT200 and sets the calculated previous measurement time to the error measurement unit 14.

[0044] The measurement time setting unit 20 sets the data rate of the output signal of the DUT200 and the target reliability level CL, which is the tolerance value of the reliability level, input to the setting screen 40 described later. S The target error rate ER is the acceptable value of the error rate of the output signal.S Based on measurement conditions such as the target number of errors E, which is the allowable number of errors during the measurement time of the output signal, the target reliability level CL is determined. S Calculate the measurement time for the output signal that gives the result. Target reliability level CL S The target error rate (ER) S This represents the probability that the true error rate of the DUT200's output signal will be lower than the given value.

[0045] As shown in Figure 2, the measurement time setting unit 20 includes an average value calculation unit 21, a provisional reliability level calculation unit 22, an upper and lower limit update unit 23, a convergence determination unit 26, a transmission speed conversion unit 27, and a measurement time calculation unit 28.

[0046] The measurement time setting unit 20 uses two variables, min_x and max_x, to determine x in equation (2) described later. x is a value greater than or equal to 0, and is greater than or equal to min_x and less than or equal to max_x. For this reason, for example, it is preferable to set the initial value of the variable min_x to 0 and the initial value of the variable max_x to the maximum significant value of the numerical type used in the calculation.

[0047] The average value calculation unit 21 calculates the sum of the value obtained by dividing the variable min_x by 2 and the value obtained by dividing the variable max_x by 2, that is, the average value x of the variables min_x and max_x. a The calculation is performed using the above-mentioned hypothetical value for x.

[0048] The average value calculation unit 21 calculates min_x / 2, max_x / 2, and x a Each value is rounded by truncating the lower digits of each value so that it fits within the maximum number of significant digits of the numeric type being used. In other words, min_x / 2, max_x / 2, and x are calculated by the average value calculation unit 21. a All of these include rounding errors. Note that the above rounding process is not limited to truncation; any other rounding method, such as rounding up, may be used.

[0049] Variable min_x, variable max_x, and mean x aThe numeric type can be, for example, a single-precision floating-point number (float type), a double-precision floating-point number (double type), or a fixed-point number. Of these, the double type is 64 bits of data consisting of a 1-bit sign part, a 52-bit mantissa part, and an 11-bit exponent part. The maximum significant value of a double type is 1.79769313486232E+308 in decimal.

[0050] The provisional reliability level calculation unit 22 calculates the average value x calculated by the average value calculation unit 21. a The provisional confidence level CLx is calculated by substituting this value into x in equation (2) below. As can be seen from equation (2), the provisional confidence level CLx increases monotonically with respect to x.

[0051]

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[0052] Furthermore, in equation (2), x:N×ER S N: Data rate [data / s] × Measurement time [s] ER S :Target Error Rate (ER) E: Target number of errors Therefore, equation (2) is N × BER of equation (1). S to N×ER S This is the result of replacing (=x).

[0053] The transmission speed conversion unit 27 converts the known baud rate of the output signal of the DUT200 to a transmission speed (data rate) corresponding to the measurement unit of the output signal of the DUT200. The baud rate of the output signal of the DUT200 may be set via a setting screen (not shown).

[0054] The data rate is a parameter that indicates the number of measurement units contained per second in the output signal of the DUT200. The measurement unit can be, for example, a bit, a symbol (PAM4 Symbol), a frit, or a codeword. Therefore, N is a parameter that indicates the number of measurement units contained in the output signal of the DUT200 over the measurement time, i.e., the number of measurement data points. The measurement unit can be set in the settings screen 40, which will be described later.

[0055] Target Error Rate (ER) S This can be, for example, BER, SER (Symbol Error Rate), Uncorrectable Codeword Rate, or Flit Error Rate, and represents the upper limit of the error rate that can be tolerated for the output signal.

[0056] "Bit" is the unit of measurement used when measuring the BER of the output signal of the DUT200. When the unit of measurement is "Bit" and the output signal of the DUT200 is an NRZ signal, the transmission speed conversion unit 27 outputs the baud rate of the output signal of the DUT200 as the data rate. When the unit of measurement is "Bit" and the output signal of the DUT200 is a PAM4 signal, the transmission speed conversion unit 27 outputs a rate obtained by doubling the baud rate of the output signal of the DUT200 as the data rate.

[0057] "PAM4 Symbol" is the unit of measurement used when measuring the SER of the output signal of the DUT200. When the unit of measurement is "PAM4 Symbol" and the output signal of the DUT200 is a PAM4 signal, the transmission speed conversion unit 27 outputs the baud rate of the output signal of the DUT200 as the data rate.

[0058] "Flit" is the unit of measurement used when measuring the Flit Error Rate of the output signal of the DUT200. When the unit of measurement is "Flit," the transmission speed conversion unit 27 outputs a data rate obtained by doubling the baud rate of the output signal of the DUT200 and dividing it by the Flit length. Here, the Flit length is 2048 bits.

[0059] "Codeword" is the unit of measurement used when measuring the Uncorrectable Codeword Rate of the output signal of the DUT200. When the unit of measurement is "Codeword," the transmission speed conversion unit 27 outputs a data rate obtained by doubling the baud rate of the output signal of the DUT200 and dividing it by the CW (Codeword) length. Here, the CW length is 5440 bits in the case of RS-FEC (Reed-Solomon Forward Error Correction) (544,514) as defined in IEEE802.3.

[0060] As already mentioned, CLx in equation (2) increases monotonically with respect to x. Therefore, the provisional reliability level CLx is equal to the target reliability level CL S If it is smaller, the mean value x when the left side of equation (2) is CLx. a The left side of equation (2) is CL S It is smaller than x when this occurs. Therefore, the upper and lower limit update unit 23 determines that the provisional reliability level CLx calculated by the provisional reliability level calculation unit 22 is less than the target reliability level CL S In the following cases, the variable min_x is set to the latest average value x a It is set up to substitute the value.

[0061] On the other hand, the provisional reliability level CLx is equal to the target reliability level CL S If it is greater than, the mean value x when the left side of equation (2) is CLx. a The left side of equation (2) is CL S It is greater than x when this occurs. Therefore, the upper and lower limit update unit 23 determines that the provisional reliability level CLx calculated by the provisional reliability level calculation unit 22 is greater than the target reliability level CL SIf it is greater than the latest average x, the variable max_x is set to the latest average x a It is set up to substitute the value.

[0062] The provisional confidence level CLx is the mean value x a Since it increases monotonically with respect to x, when the processing by the average value calculation unit 21, the provisional reliability level calculation unit 22, and the upper and lower limit update unit 23 is repeated, the variable min_x will always be the average value x a The variable max_x always takes a value smaller than the mean x a While taking values ​​larger than this, max_x - min_x converges to 0.

[0063] In other words, through the repeated process described above, the average value x a The range of values ​​is narrowed down, and finally max_x = min_x = x, resulting in the target reliability level CL S An approximate value of x that gives the result can be obtained. Figure 3 shows the average value x calculated by the average value calculation unit 21, the provisional reliability level calculation unit 22, and the upper and lower limit update unit 23. a This is a diagram to explain the filtering process.

[0064] First, the average value calculation unit 21 uses the initial values ​​of the variables min_x and max_x to calculate the average value x a Calculate (Step S1).

[0065] Next, the provisional reliability level calculation unit 22 calculates the average value x calculated in step S1. a Substitute this into equation (2) to calculate the provisional reliability level CLx. The upper and lower limit update unit 23 checks if the provisional reliability level CLx calculated by the provisional reliability level calculation unit 22 is equal to the target reliability level CL S If it is greater than the latest average x, the variable max_x is set to the latest average x a The value is substituted. The average value calculation unit 21 uses the initial value of the variable min_x and the updated variable max_x to calculate the average value x again. a Calculate (Step S2).

[0066] Next, the provisional reliability level calculation unit 22 calculates the average value x calculated in step S2. aSubstitute this into equation (2) to calculate the provisional reliability level CLx. The upper and lower limit update unit 23 checks if the provisional reliability level CLx calculated by the provisional reliability level calculation unit 22 is equal to the target reliability level CL S In the following cases, the variable min_x will contain the latest average value x a Substitute the values. The average value calculation unit 21 uses the updated variables min_x and max_x to calculate the average value x again. a Calculate (Step S3).

[0067] Next, the provisional reliability level calculation unit 22 calculates the average value x calculated in step S3. a Substitute this into equation (2) to calculate the provisional reliability level CLx. The upper and lower limit update unit 23 checks if the provisional reliability level CLx calculated by the provisional reliability level calculation unit 22 is equal to the target reliability level CL S If it is greater than the latest average x, the variable max_x is set to the latest average x a Substitute the values. The average value calculation unit 21 uses the variables min_x and the updated variable max_x to calculate the average value x again. a Calculate (Step S4).

[0068] In other words, the average value calculation unit 21 uses the latest variables min_x and max_x to calculate the latest average value x a The provisional reliability level calculation unit 22 calculates the latest average value x a Substitute this into equation (2) to calculate the provisional reliability level CLx. Then, the upper and lower limit update unit 23 sets the variable min_x or the variable max_x to the latest average value x according to the latest provisional reliability level CLx. a Substitute the values. In this way, the measurement time setting unit 20 uses the latest variables min_x and max_x to calculate the average value x calculated by the average value calculation unit 21, the provisional reliability level calculation unit 22, and the upper and lower limit update unit 23. a The filtering process is repeated.

[0069] The convergence determination unit 26 determines the average value x calculated by the average value calculation unit 21. aThe system determines whether the change in the value of has converged to a predetermined range. For example, the convergence determination unit 26 determines whether the average value x calculated by the average value calculation unit 21 has converged to a predetermined range. a This could also be a method for determining whether the significant figures of have converged to a certain value. Variables min_x, max_x, and mean x a If the numeric type is double, then the variables min_x, max_x, and mean x a The significant figures are the mantissa of type double.

[0070] The convergence determination unit 26 determines, for example, the latest average value x a and the previous average value x a If they are equal, the mean x a The convergence determination unit 26 determines that the number of significant figures has converged to a certain value. Alternatively, the convergence determination unit 26 determines that the average value x calculated by the average value calculation unit 21 has converged to a certain value. a If the values ​​are equal for any number of consecutive times (3 or more), the mean value x a It may also be determined that the number of significant figures has converged to a certain value.

[0071] Figure 4 shows the variables min_x, max_x, and mean x. a This table shows the changes in each value when the numerical type of is double. Figure 5 also shows the variables min_x, max_x, and the mean x as shown in Figure 4. a In the change of the mean x, a This graph shows the data around the point where the curve converges. Here, the output signal of DUT200 is assumed to be an NRZ signal, with a data rate of 2.4 Gbps and a target error rate ER as the basis for the reliability level. S The target error count E, which serves as the basis for the reliability level, is 3, and the target reliability level CL is 1E-12. S It is stated that this is 0.98.

[0072] In the example in Figure 4, although the value of min_x changes in the 1071st and 1072nd calculation results, x a We can see that the value of x has not changed. This is due to rounding error. a This indicates that the value has converged.

[0073] Note that in the calculation results of the 1069th to 1072nd times, CL S and CLx are the same. However, depending on the input value to Equation (2), before CL S and CLx become the same, x a may converge. Therefore, it is not desirable to use whether CL S and CLx are the same as the end determination condition for the narrowing-down process of the average value x a .

[0074] When using, for example, the double type as the numerical type of the variable min_x, the variable max_x, and the average value x a , a result with about 14 significant digits in decimal conversion can be obtained. The number of repetitions of the narrowing-down process of the average value x a is a finite number of about 1000 times, and the time required for 1000 repetitions is about several tens of ms. Therefore, it is considered that the narrowing-down process of the average value x a is unlikely to impair the convenience of the user.

[0075] Also, in this narrowing-down process, the convergence of the average value x a due to the rounding error is used as the end determination condition of the process. For this reason, the user does not need to consider the range considered as the value of the average value x a and the number of repetitions of the process every time various measurement conditions are changed on the setting screen 40.

[0076] Alternatively, the convergence determination unit 26 may not wait for the convergence of the average value x a due to the rounding error, but may determine whether the change in the value of the average value x a calculated by the average value calculation unit 21 has become less than or equal to a predetermined value with a number of digits less than the maximum significant digits of the numerical type being used. In this case, although the number of significant digits decreases, it is possible to further speed up the narrowing-down process.

[0077] The measurement time calculation unit 28 calculates the average value x calculated by the average value calculation unit 21 and determined to have converged by the convergence determination unit 26, as shown in equation (3) below. a The data rate and target error rate ER converted by the transmission speed conversion unit 27 S The measurement time is calculated by dividing by the product of the two values.

[0078] Measurement time [s]=x a / (Data rate [data / s] × ER S ) ···(3)

[0079] The operation unit 31 is for receiving user input and consists of a user interface such as an operation knob, various keys, switches, buttons, and soft keys on the display screen of the display unit 32, which are provided by the jitter tolerance measuring device 1 shown in Figure 1. The operation unit 31 also performs various settings related to jitter tolerance measurement of the jitter tolerance measuring device 1 and sets various measurement conditions on the setting screen 40.

[0080] The display unit 32 is comprised of a display device such as an LCD (Liquid Crystal Display) or CRT (Cathode Ray Tube), which is part of the jitter tolerance measuring device 1 shown in Figure 1. Based on display control signals from the control unit 15, it displays the setting screen 40, measurement results, and the like. The display unit 32 may also have operating functions for the operation unit 31, such as soft keys on the display screen.

[0081] As shown in Figure 6, the display unit 32 displays a setting screen 40 for setting the measurement conditions for the jitter tolerance of the output signal of the DUT200.

[0082] The setting screen 40 includes the pull-down menus 41a, 41b of "Unit", the radio buttons 42a of "Gating", the radio buttons 42b of "Target Confidence Level", the spin box 43 of "Gating", the spin box 44 of "Target Confidence Level", the spin boxes 45a, 45b of "Target ER", the spin box 46 of "Target EC", and the soft key 47 of "Close".

[0083] The pull-down menu 41a of "Unit" enables the error measurement unit 14 to select whether to measure the number of errors or the error rate of the output signal of the DUT 200. The pull-down menu 41b of "Unit" enables the selection of the measurement unit of the number of errors or the error rate set in the pull-down menu 41a of "Unit" from, for example, Bit, PAM4 Symbol, Flit, or Codeword.

[0084] The radio button 42a of "Gating" and the radio button 42b of "Target Confidence Level" enable the selection of whether to set the measurement time in the spin box 43 of "Gating" or to set the target confidence level CL S in the spin box 44 of "Target Confidence Level".

[0085] When the radio button 42a of "Gating" is selected, the spin box 43 of "Gating" enables the input of the measurement time in units of 1 second within the range of, for example, 1 second to 86400 seconds.

[0086] Furthermore, when the "Target Confidence Level" radio button 42b is selected, the "Gating" spin box 43 becomes unresponsive, and displays the measurement time calculated by the measurement time calculation unit 28 in increments of one second, for example, within a range of 1 to 172800 seconds. In other words, the "Gating" spin box 43 constitutes a measurement time display unit that displays the measurement time of the output signal of the DUT200.

[0087] The spin box 44 for "Target Confidence Level" is set to target confidence level CL when the radio button 42b for "Target Confidence Level" is selected. S For example, it is possible to input a value in 0.1% increments within the range of 0.0 to 99.9%. In other words, the spin box 44 for "Target Confidence Level" is set to the desired target confidence level CL. S This configures a target reliability level input section for inputting the target reliability level.

[0088] Furthermore, when the "Gating" radio button 42a is selected, the spin box 44 for "Target Confidence Level" becomes unusable, and the target confidence level CL calculated by means not shown in the diagram is disabled. S It is set to display, for example, in a range of 0.0 to 99.9%.

[0089] The "Target ER" spin boxes 45a and 45b control the desired target error rate ER of the output signal of the DUT200. s The spin boxes 45a and 45b constitute the target error rate input section for inputting the target error rate ER. s The system allows input in exponential notation, with the mantissa being entered in spin box 45a and the exponent in spin box 45b. For example, spin boxes 45a and 45b can accept values ​​in the range of 1E-15 to 9E-3.

[0090] The "Target EC" spin box 46 constitutes the target error input section for inputting the target error number E during the measurement time of the DUT200's output signal. For example, the spin box 46 can accept values ​​in the range of 0 to 10. The unit of the target error number E input to the spin box 46 changes according to the measurement unit selected in the "Unit" pull-down menu 41b.

[0091] If there are any changes to the input content of spin box 44 for "Target Confidence Level," spin boxes 45a and 45b for "Target ER," or spin box 46 for "Target EC," the display of the measurement time calculation result in spin box 43 for "Gating" will also be automatically updated.

[0092] Here, the "Gating" spin box 43 displays the number of seconds of the measurement time calculated by the measurement time calculation unit 28, for example, by rounding up to the first decimal place. In the example in Figure 4, the average value x of the 1071st and 1072nd measurements is displayed. a The value is 9.08411538241318E+00, and the measurement time calculated from equation (3) is 3.78504807600549E+03[s]. At this time, "3785" is displayed on the spin box 43.

[0093] When the user presses the "Close" soft key 47, the measurement time setting unit 20 incorrectly sets the measurement time currently displayed in the "Gating" spin box 43 to the measurement unit 14 and ends the display of the setting screen 40.

[0094] The following describes an example of a jitter tolerance measurement method using the jitter tolerance measuring device 1 of this embodiment, with reference to the flowchart in Figure 7. Note that explanations that overlap with the above-described explanation of the configuration of the jitter tolerance measuring device 1 will be omitted as appropriate.

[0095] First, the control unit 15 displays a setting screen 40 on the display unit 32 for setting the measurement conditions for the jitter tolerance of the output signal of the DUT200 (setting screen display step S21).

[0096] Next, the user can set the target reliability level CL via the operating unit 31. S , unit of measurement for error rate, target error rate ER of the output signal s The measurement conditions, such as the target number of errors E during the measurement time of the output signal, are entered into the setting screen 40 (input step S22).

[0097] Next, the transmission speed conversion unit 27 converts the baud rate of the output signal of the DUT200 to a transmission speed (data rate) corresponding to the measurement unit entered in the setting screen 40 in input step S22 (transmission speed conversion step S23).

[0098] Next, the measurement time setting unit 20 sets the data rate converted in the transmission speed conversion step S23 and the target reliability level CL, which was input to the setting screen 40 in the input step S22. S Target error rate ER S Based on the target number of errors E, the target reliability level CL S The measurement time required to obtain the result is calculated (measurement time calculation step S24).

[0099] Next, the display unit 32 displays the measurement time calculated in the measurement time calculation step S24 in the "Gating" spin box 43 (measurement time display step S25).

[0100] Next, when the user presses the "Close" soft key 47 on the settings screen 40, the measurement time setting unit 20 sets the measurement time currently displayed in the "Gating" spin box 43 on the settings screen 40 to the measurement unit 14 (measurement time setting step S26).

[0101] Next, the jitter tolerance measurement unit 16 sets a predetermined jitter frequency to the jitter modulation signal output unit 11 (step S27).

[0102] Next, the jitter tolerance measurement unit 16 sets a predetermined jitter amplitude to the jitter modulation signal output unit 11 (step S28).

[0103] Next, the pattern signal generation unit 13 outputs a phase-modulated pattern signal to the DUT 200 according to the jitter frequency and jitter amplitude set in steps S27 and S28 (step S29).

[0104] Next, the error measurement unit 14 counts the number of errors in the output signal of the DUT200 and calculates the error rate of the output signal of the DUT200 over the measurement time set by the measurement time setting unit 20 in step S26 (error calculation step S30).

[0105] Next, the jitter tolerance measurement unit 16 determines whether the number of errors or the error rate obtained in the error calculation step S30 is below a predetermined allowable value (step S31).

[0106] If the number of errors or error rate obtained in the error calculation step S30 is below a predetermined tolerance value (step S31: YES), in step S28, the jitter tolerance measurement unit 16 sets an even larger jitter amplitude to the jitter modulation signal output unit 11. In this flowchart, the process in step S28 is to gradually increase the jitter amplitude from a predetermined minimum value for each jitter frequency.

[0107] If the number of errors or error rate obtained in the error calculation step S30 is greater than a predetermined tolerance value (step S31: NO), in step S32 the jitter tolerance measurement unit 16 estimates the maximum jitter amplitude at which the number of errors or error rate obtained in the error calculation step S30 is less than or equal to a predetermined tolerance value as the jitter tolerance at the currently set jitter frequency (step S32).

[0108] If the jitter tolerance estimation process in step S32 has not been completed for all predetermined jitter frequencies (step S33: NO), in step S27, the jitter tolerance measurement unit 16 sets a new jitter frequency in the jitter modulation signal output unit 11.

[0109] When the jitter tolerance estimation process in step S32 is completed for all predetermined jitter frequencies (step S33: YES), the control unit 15 terminates the process of the series of jitter tolerance measurement methods described above.

[0110] As described above, the jitter tolerance measuring device 1 according to this embodiment achieves a desired target reliability level CL S The system automatically calculates the measurement time required to obtain the desired result, and error measurements to obtain the jitter tolerance of the DUT200 can be performed over the calculated measurement time.

[0111] In other words, the jitter tolerance measuring device 1 according to this embodiment allows the user to set a desired target reliability level CL on the setting screen 40. S By setting this, it becomes possible to calculate the measurement time without any hassle and to start jitter tolerance measurement immediately.

[0112] Furthermore, the jitter tolerance measuring device 1 according to this embodiment measures the average value x in error measurement of the output signal. a By performing a filtering process, the desired target reliability level CL can be achieved without the user being aware that the measurement time calculation process is taking place. S The measurement time required to obtain the desired result can be calculated.

[0113] Furthermore, the jitter tolerance measuring device 1 according to this embodiment uses an average value x to determine the convergence due to rounding error. a Since this is used as the termination condition for the filtering process, the average value x a This eliminates the need for the user to consider the possible range of values ​​and the number of times the process should be repeated each time the various measurement conditions are changed on the settings screen 40.

[0114] Furthermore, the jitter tolerance measuring device 1 according to this embodiment uses the variables min_x, max_x, and average value x. a If the numeric type is double, the average value x will have approximately 14 significant digits when converted to decimal. a The measurement time can be calculated using this method. [Explanation of Symbols]

[0115] 1. Jitter tolerance measuring device 10 Jitter generation section 11. Jitter Modulation Signal Output Section 12. Jitter Clock Output Section 13 Pattern signal generation unit 14 Error Measurement Unit 15 Control Unit 16. Jitter tolerance measurement section 20 Measurement time setting section 21. Average value calculation section 22 Provisional Reliability Level Calculation Unit 23 Upper and Lower Limit Update Section 26 Convergence determination unit 27 Transmission speed conversion unit 28 Measurement time calculation unit 30 Data storage unit 31 Operation section 32 Display section 40 Settings screen 41a, 41b Pull-down menu 42a, 42b Radio buttons 43, 44, 45a, 45b, 46 Spin Box 200 DUT

Claims

1. A jitter modulation signal output unit (11) outputs a jitter modulation signal with variable jitter amplitude and jitter frequency, A jitter clock output unit (12) receives the jitter modulated signal from the jitter modulated signal output unit and outputs a phase-modulated jitter clock according to the jitter amplitude and the jitter frequency, A pattern signal generation unit (13) outputs a pattern signal synchronized with the jitter clock to the object under measurement, An error measurement unit (14) that measures the number of errors and the error rate of the output signal of the object under test that has received the pattern signal over a predetermined measurement period, A jitter tolerance measuring unit (16) changes the jitter amplitude and jitter frequency of the jitter modulated signal output by the jitter modulated signal output unit, and estimates the maximum jitter amplitude at which the number of errors or error rate measured by the error measurement unit is less than or equal to a predetermined tolerance value, as the jitter tolerance of the object under test for each jitter frequency, A measurement time setting unit (20) calculates the measurement time of the output signal and sets the calculated measurement time in the error measurement unit, The system includes a display unit (32) that displays a setting screen (40) for setting the measurement conditions for the jitter tolerance, The aforementioned settings screen is, A target reliability level input unit (44) for inputting an acceptable value for the reliability level, A target error rate input unit (45a, 45b) for inputting the allowable value of the error rate of the output signal, A target error count input unit (46) for inputting an acceptable value for the number of errors in the output signal during the measurement time, It includes a measurement time display unit (43) that displays the measurement time of the output signal, The measurement time setting unit calculates the measurement time that gives the tolerance value for the reliability level based on the data rate of the output signal, the tolerance value for the reliability level, the tolerance value for the error rate, and the tolerance value for the number of errors, which are input to the setting screen. The measurement time setting unit is, An average value calculation unit (21) calculates the average value x a of the variables min_x and max_x, A provisional reliability level calculation unit (22) calculates the provisional reliability level CLx by substituting the aforementioned average value x a into x in the following formula (2), The system includes an upper and lower limit update unit (23) that, when the provisional reliability level CLx is less than or equal to the allowable value of the reliability level, substitutes the average value x a into the variable min_x, and when the provisional reliability level CLx is greater than the allowable value of the reliability level, substitutes the average value x a into the variable max_x, The measurement time setting unit is, Using the latest variables min_x and max_x, the processes of the average value calculation unit, the provisional reliability level calculation unit, and the upper and lower limit update unit are repeated. A jitter tolerance measuring device further comprising a measurement time calculation unit (28) that, when the change in the value of the average value x a calculated by the average value calculation unit converges to a predetermined range, calculates the measurement time as the value obtained by dividing the converged average value x a by the product of the data rate and the allowable value of the error rate. [Math 1]

2. The average value x a calculated by the average value calculation unit includes rounding errors, The jitter tolerance measuring device according to claim 1, characterized in that the measurement time calculation unit calculates the measurement time as the value obtained by dividing the converged average value x a by the product of the data rate and the allowable value of the error rate when the significant figures of the average value x a converge to a certain value.

3. The average value x a is double-precision floating-point data, The jitter tolerance measuring device according to claim 2, characterized in that the significant figures are the mantissa portion of a double-precision floating-point number.

4. A jitter modulation signal output unit (11) that outputs a jitter modulation signal with variable jitter amplitude and jitter frequency, A jitter clock output unit (12) receives the jitter modulated signal from the jitter modulated signal output unit and outputs a phase-modulated jitter clock according to the jitter amplitude and the jitter frequency, A pattern signal generation unit (13) outputs a pattern signal synchronized with the jitter clock to the object under measurement, An error measurement unit (14) that measures the number of errors and the error rate of the output signal of the object under test that has received the pattern signal over a predetermined measurement period, A jitter tolerance measurement method using a jitter tolerance measuring device (1) comprising: a jitter tolerance measuring unit (16) that changes the jitter amplitude and jitter frequency of the jitter modulated signal output by the jitter modulated signal output unit, and estimates the maximum jitter amplitude for which the number of errors or error rate measured by the error measurement unit is less than or equal to a predetermined tolerance value, as the jitter tolerance of the object under test for each jitter frequency, wherein the jitter tolerance measuring device (1) is used, A setting screen display step (S21) is performed, in which a setting screen (40) for setting the measurement conditions for the jitter tolerance is displayed on the display unit (32), An input step (S22) in which the tolerance value for the reliability level, the tolerance value for the error rate, and the tolerance value for the number of errors are entered into the setting screen, A measurement time calculation step (S24) is performed to calculate the measurement time that gives the tolerance value of the reliability level based on the data rate of the output signal, the tolerance value of the reliability level, the tolerance value of the error rate, and the tolerance value of the number of errors, which are entered into the setting screen. A measurement time display step (S25) which displays the measurement time calculated in the measurement time calculation step, The measurement time setting step (S26) includes setting the measurement time calculated in the measurement time calculation step to the error measurement unit, The aforementioned settings screen is, A target reliability level input unit (44) for inputting the tolerance value of the reliability level, A target error rate input unit (45a, 45b) for inputting the allowable value of the error rate of the output signal, A target error count input unit (46) for inputting an acceptable value for the number of errors in the output signal during the measurement time, It includes a measurement time display unit (43) that displays the measurement time of the output signal, The measurement time calculation step is: The average value calculation step calculates the average value x a of the variables min_x and max_x, A provisional reliability level calculation step involves substituting the aforementioned average value x a into x in the following equation (2) to calculate the provisional reliability level CLx, An upper and lower limit update step in which the average value x a is substituted into the variable min_x when the provisional reliability level CLx is less than or equal to the tolerance value of the reliability level, and the average value x a is substituted into the variable max_x when the provisional reliability level CLx is greater than the tolerance value of the reliability level, The process of repeating the steps of calculating the average value, calculating the provisional reliability level, and updating the upper and lower limits using the latest variables min_x and max_x, A jitter tolerance measurement method characterized by including the step of, when the change in the value of the average value x a calculated in the average value calculation step converges to a predetermined range, calculating the value obtained by dividing the converged average value x a by the product of the data rate and the allowable value of the error rate as the measurement time. [Math 2]

5. The average value x a calculated by the average value calculation step includes rounding errors, The jitter tolerance measurement method according to claim 4, characterized in that the measurement time calculation step is performed by, when the number of significant figures of the average value x a converges to a certain value, calculating the measurement time as the value obtained by dividing the converged average value x a by the product of the data rate and the allowable value of the error rate.

6. The average value x a is double-precision floating-point data, The jitter tolerance measurement method according to claim 5, characterized in that the significant figures are the mantissa part of a double-precision floating-point number.

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