Bit error rate measurement device and bit error rate measurement method

Abstract

Provided are a bit error rate measurement device and a bit error rate measurement method with which it is possible to calculate a measurement time at which a desired reliability level can be obtained in bit error rate measurement of an input signal. A bit error rate measurement device is provided with: an average value calculation unit (31) that calculates the sum x of a value obtained by dividing a variable minx by 2 and a value obtained by dividing a variable maxx by 2; a provisional reliability level calculation unit (32) that uses the sum x to calculate a provisional reliability level CLx; an upper / lower limit value updating unit (33) that, when the provisional reliability level CLx is equal to or less than the target reliability level CLS, substitutes a sum x into a variable minx, and when the provisional reliability level CLx is greater than the target reliability level CLS, substitutes a sum x into a variable maxx; and a measurement time calculation unit (38) that, when the change in the value of the sum x calculated by the average value calculation unit (31) falls within a prescribed range, calculates, as the measurement time, the value obtained by dividing the converged sum x by the product of the data transmission rate and the target error rate (ERS).

Description

Technical Field

[0001] The present invention relates to a bit error rate measuring device and a bit error rate measuring method for measuring the bit error rate of a signal input from a measured object. Background Art

[0002] Conventionally, a bit error rate tester (BERT) measures the bit error rate (error rate) (see, for example, Patent Documents 1 to 3). The bit error rate measurement is a very important analysis method for evaluating the performance of various communication devices as a test object.

[0003] Most errors generated in actual systems are caused by random noise, and the error time is random. In addition, in a system using a decision feedback equalizer (DFE), random errors may become burst errors.

[0004] Therefore, the reliability of the bit error rate (BER) is usually evaluated using the confidence level defined by the following formula (1) under the condition of E ≥ 1. Here, the reliability level CL of formula (1) represents the probability that the actual BER of the system becomes smaller than the target BER (target BER).

[0005] [Formula 1]

[0006]

[0007] In addition, in formula (1),

[0008] N: bit rate [bit / s] × measurement time [s] (number of measured bits);

[0009] BER S : target BER;

[0010] E: The number of assumed errors.

[0011] For a predefined target BER, the measurement time required to achieve the desired reliability level CL varies depending on the desired reliability level CL or bit rate. For example, when performing error-free measurement, if E = 0, then if BER S and CL, it is relatively simple to solve N for equation (1). However, when E ≥ 1, it is mathematically difficult to solve N for equation (1), which is not practical.

[0012] Patent Document 1: Japanese Patent No. 6818056

[0013] Patent Document 2: Japanese Patent Application Publication No. 2007-155457

[0014] Patent Document 3: Japanese Patent Application Publication No. 2017-538367

[0015] That is, when the error number E is assumed to be 1 or more, conventional bit error rate measurement devices such as those disclosed in Patent Documents 1 to 3 cannot automatically evaluate how long the measurement time needs to be in order to achieve a required reliability level.

[0016] In fact, the measurement time step set by the user is 1 second or 0.1 second, and there is no need to strictly calculate the measurement time mathematically. For example, when the bit rate = 32 Gbit / s and BER S =1E-10, E=2, the reliability level CL relative to the measurement time is as follows Fig. 9 For example, the measurement time when CL = 95% is about 1.967 seconds, but in reality, an accuracy of 2 seconds (CL = 95.36%) is sufficient.

[0017] However, conventionally, users have had to gradually change the measurement time substituted into equation (1) to search for a measurement time that can achieve a desired reliability level CL, or set the measurement time to be slightly longer, which has led to a problem of reduced work efficiency.

[0018] Furthermore, currently, there are many types of errors measured by the bit error rate measurement device, and not only the BER of the NRZ (Non Return to Zero) signal (hereinafter, also referred to as "NRZ signal"), but also the symbol error rate (SER) of the PAM4 (Pulse Amplitude Modulation 4) signal (hereinafter, also referred to as "PAM4 signal") is added to the evaluation index. Moreover, under the standard based on forward error correction (FEC) such as 400GbE (Gigabit Ethernet) or PCIe (registered trademark) (Peripheral Component Interconnect Express) Gen (Generation) 6, not only the evaluation of BER or SER, but also the indicators of whether the error correction based on FEC is completed, such as "Uncorrectable Codeword Rate" or "Flit Error Rate", are also important. In addition, Flit is a flow control unit. Summary of the invention

[0019] The present invention has been made to solve such conventional problems, and an object of the present invention is to provide a bit error rate measurement device and a bit error rate measurement method capable of calculating a measurement time for obtaining a desired reliability level in bit error rate measurement of an input signal.

[0020] In order to solve the above-mentioned problems, the bit error rate measurement device involved in the present invention measures the bit error rate of the input signal from the object under test 200. The bit error rate measurement device 1 has the following structure, that is, it has a processing unit 30, and the processing unit 30 calculates the measurement time that meets the target reliability level according to the target reliability level, the data transmission rate of the input signal, the target bit error rate of the input signal and the assumed number of errors E within the measurement time of the input signal. The processing unit includes: an average value calculation unit 31, which calculates the sum x of the value of the variable min_x divided by 2 and the value of the variable max_x divided by 2; a provisional reliability level calculation unit 32, which substitutes the sum x into the following formula 2 to calculate the provisional reliability level CLx; an upper and lower limit value updating unit 33, when the provisional reliability level CLx is the target reliability level When the provisional reliability level CLx is below the target reliability level, the sum x is substituted into the variable min_x; when the provisional reliability level CLx is greater than the target reliability level, the sum x is substituted into the variable max_x; a convergence determination unit 36 ​​determines whether the change in the value of the sum x calculated by the average value calculation unit converges within a specified range; and a measurement time calculation unit 38, when the convergence determination unit determines that it has converged, calculates the converged sum x divided by the product of the data transmission rate and the target bit error rate as the measurement time, and when the convergence determination unit does not determine that it has converged, the processing unit uses the latest variable min_x and the latest variable max_x to repeat the processing of the average value calculation unit, the provisional reliability level calculation unit and the upper and lower limit value updating unit.

[0021] [Formula 2]

[0022]

[0023] According to this configuration, the bit error rate measurement device of the present invention can calculate the measurement time for obtaining the desired target reliability level by performing the narrowing process of x in the bit error rate measurement of the input signal without making the user aware of the measurement time calculation process.

[0024] Furthermore, the bit error rate measurement device involved in the present invention can be configured as follows, namely, the sum x calculated by the average value calculation unit includes rounding errors, and when the significant digits of the sum x converge to a certain value, the measurement time calculation unit calculates the converged sum x divided by the product of the data transmission rate and the target bit error rate as the measurement time.

[0025] According to this structure, the bit error rate measurement device involved in the present invention sets the convergence based on the rounding error as the end judgment condition of the reduction range processing of the sum x, thereby eliminating the user's labor and time of considering the range of values ​​considered to be the sum x or the number of times the processing is repeated every time various measurement conditions are changed on the setting screen.

[0026] Furthermore, the bit error rate measurement device according to the present invention may have the following structure, that is, the sum x is double-precision floating point data, and the significant digit is the significant digit of the double-precision floating point number.

[0027] According to this configuration, when the numerical types of the variable min_x, the variable max_x, and the sum x are double-precision floating point numbers, the bit error rate measurement device according to the present invention can count the measurement time using the sum x having approximately 14 significant digits in decimal conversion.

[0028] Furthermore, the bit error rate measurement device according to the present invention may be configured to further include a bit error rate calculation unit 25 for calculating the bit error rate of the input signal within the measurement time calculated by the measurement time calculation unit.

[0029] According to this configuration, the bit error rate measurement device according to the present invention can calculate the bit error rate of the input signal within a measurement time that can achieve a desired target reliability level.

[0030] Furthermore, the bit error rate measurement method involved in the present invention measures the bit error rate of the input signal from the object under test 200, and the bit error rate measurement method may be structured as follows, namely, comprising: an input step S22, inputting the target reliability level, the data transmission rate of the input signal, the target bit error rate of the input signal, and the assumed number of errors E within the measurement time of the input signal; a step S24, setting initial values ​​for the variables min_x and max_x; an average value calculation step S25, calculating the sum x of the value of the variable min_x divided by 2 and the value of the variable max_x divided by 2; a provisional reliability level calculation step S27, substituting the sum x into the following formula 2 to calculate the provisional reliability level CLx; a lower limit value update step S29, when the provisional reliability level CLx is the target When the reliability level is below the target reliability level, the sum x is substituted into the variable min_x; an upper limit value updating step S30, when the provisional reliability level CLx is greater than the target reliability level, the sum x is substituted into the variable max_x; a step S26, using the latest variable min_x and the latest variable max_x to repeat the processing of the average value calculation step, the provisional reliability level calculation step, the lower limit value updating step and the upper limit value updating step; and a measurement time calculation step S31, when the change of the value of the sum x calculated in the average value calculation step converges to a specified range, the converged sum x divided by the product of the data transmission rate and the target bit error rate is calculated as the measurement time that meets the target reliability level.

[0031] [Formula 3]

[0032]

[0033] Furthermore, the bit error rate measurement method involved in the present invention can be structured as follows, that is, the sum x calculated in the average value calculation step includes rounding errors, and when the significant digits of the sum x converge to a certain value, the measurement time calculation step calculates the converged sum x divided by the product of the data transmission rate and the target bit error rate as the measurement time.

[0034] Furthermore, the bit error rate measurement method involved in the present invention may have the following structure, that is, the sum x is double-precision floating point data, and the significant digit is the significant digit of the double-precision floating point number.

[0035] Furthermore, the bit error rate measurement method involved in the present invention may have the following structure, that is, further comprising: a bit error rate calculation step S34, calculating the bit error rate of the input signal within the measurement time calculated in the measurement time calculation step.

[0036] Effects of the Invention

[0037] The present invention provides a bit error rate measurement device and a bit error rate measurement method which can calculate the measurement time for obtaining a desired reliability level in the bit error rate measurement of an input signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a block diagram showing the structure of a bit error rate measurement device according to an embodiment of the present invention.

[0039] Figure 2 It is a block diagram showing the configuration of a processing unit included in the bit error rate measurement device according to the embodiment of the present invention.

[0040] Figure 3 It is an explanatory diagram for explaining the operation of a processing unit included in the bit error rate measurement device according to the embodiment of the present invention.

[0041] Figure 4 This is a table showing changes in each value when the numeric type is a double type (double-precision floating point type).

[0042] Figure 5 This is a graph showing changes in each value when the numeric type is double type.

[0043] Figure 6 This is an example of a setting screen of the bit error rate measurement device according to the embodiment of the present invention.

[0044] Figure 7 This is a table showing measurement units and the data transfer rate for each measurement unit.

[0045] Figure 8 This is a flowchart showing the processing of a bit error rate measurement method using the bit error rate measurement device according to the embodiment of the present invention.

[0046] Fig. 9 This is a graph showing an example of reliability level with respect to measurement time. DETAILED DESCRIPTION

[0047] Hereinafter, embodiments of a bit error rate measurement device and a bit error rate measurement method according to the present invention will be described with reference to the drawings.

[0048] like Figure 1 As shown, the bit error rate measurement device 1 according to the embodiment of the present invention measures the bit error rate of an input signal output from a device under test (DUT) 200 and includes a signal output unit 10 , a signal input unit 20 , a data storage unit 40 , an operation unit 41 , a display unit 42 , and a control unit 43 .

[0049] Examples of standards compatible with DUT 200 include PCIe Gen1 to 6, USB (registered trademark) (Universal Serial Bus) 3.1 to 4, CEI (Common Electrical Interface), IEEE802.3, InfiniBand HDR (InfiniBand High Dynamic Range), and Fibre Channel.

[0050] The data storage unit 40 is composed of a memory such as a RAM (Random Access Memory). The data storage unit 40 stores, for example, bit string data of an NRZ signal (data of a bit string consisting of 0 or 1) or symbol string data of a PAM4 signal (data of a symbol string consisting of 0, 1, 2, or 3) as signal data of a known pattern input to the DUT 200 from the signal output unit 10 described later.

[0051] Furthermore, the data storage unit 40 may store the bit string data of the MSB (Most Significant Bit) and the LSB (Least Significant Bit) of the PAM4 signal input to the DUT 200. The symbol string data of the PAM4 signal, the bit string data of the MSB and the LSB, and the bit string data of the NRZ signal stored in the data storage unit 40 also become reference data for comparison with the input signal from the DUT 200 by the bit error rate calculation unit 25 described later.

[0052] The signal output unit 10 generates a test signal composed of data of a known pattern input from the data storage unit 40. Then, the signal output unit 10 outputs the generated test signal to the DUT 200. At this time, the DUT 200 returns the test signal output from the signal output unit 10 as an input signal to the signal input unit 20.

[0053] The signal input unit 20 receives an input signal output from the DUT 200 , and includes an equalizer 21 and a bit error rate measurement unit 22 .

[0054] The input signal from the DUT 200 is, for example, a signal obtained by returning a test signal such as a PAM4 signal output from the signal output unit 10 from the DUT 200 .

[0055] The equalizer 21 adjusts the frequency characteristics of the input signal from the DUT 200. The equalizer 21 is composed of, for example, a CTLE (Continuous Time Linear Equalizer), an LFE (Low Frequency Equalizer), a DFE, and the like.

[0056] The bit error rate measurement section 22 includes a clock regeneration section 23 , a data extraction section 24 , a bit error rate calculation section 25 , and a processing section 30 , and performs bit error rate measurement of an input signal from the DUT 200 .

[0057] The clock recovery unit 23 generates a recovered clock signal based on the input signal from the DUT 200 adjusted by the equalizer 21 .

[0058] The data extraction unit 24 extracts bit string data or symbol string data of the input signal from the DUT 200 adjusted by the equalizer 21 .

[0059] The data extraction unit 24 accesses the input signal adjusted by the equalizer 21 at the timing of the rise or fall of the clock signal, and extracts the bit string data or the symbol string data of the input signal output from the DUT 200. Here, the clock signal used by the data extraction unit 24 may be the regenerated clock signal output from the clock regeneration unit 23, or may be an external clock signal corresponding to the baud rate of the input signal. In this specification, the regenerated clock signal and the external clock signal are collectively referred to as the "clock signal".

[0060] For example, the data extraction unit 24 includes a plurality of 0 / 1 determiners, and a clock signal is input to each 0 / 1 determiner, thereby being able to determine the level of the input signal output from the DUT 200 at the timing of the clock signal. In addition, the regenerated clock signal output from the clock regeneration unit 23 is not limited to the data extraction unit 24, and can also be used as an operation clock in each unit constituting the bit error rate measurement device 1.

[0061] The bit error rate calculation unit 25 calculates the bit error rate of the input signal from the DUT 200 extracted by the data extraction unit 24 by sequentially comparing the bit string data or symbol string data extracted by the data extraction unit 24 with the reference data stored in the data storage unit 40. In addition, in this specification, BER, SER, Uncorrectable Codeword Rate and Flit Error Rate are collectively referred to as "bit error rate".

[0062] The bit error rate calculation unit 25 counts the number of errors of the input signal from the DUT 200 during the measurement time set by the setting screen 50 described later or the measurement time calculated by the measurement time calculation unit 38 described later. The bit error rate calculation unit 25 calculates the value obtained by dividing the counted number of errors by the number of measurement data of the input signal during the measurement time as the bit error rate of the input signal from the DUT 200.

[0063] The processing unit 30 determines the target reliability level CL inputted into the setting screen 50 described later. S , data transmission rate of the input signal, target bit error rate ER of the input signalS The target reliability level CL is calculated based on the measurement conditions such as the assumed number of errors E within the measurement time of the input signal. S Target reliability level CL S Indicates the target bit error rate ER S The probability that the actual bit error rate of the input signal from DUT 200 becomes smaller.

[0064] like Figure 2 As shown, the processing unit 30 includes an average value calculation unit 31 , a provisional reliability level calculation unit 32 , an upper and lower limit value update unit 33 , a convergence determination unit 36 ​​, a transmission rate conversion unit 37 , and a measurement time calculation unit 38 .

[0065] The average value calculation unit 31 calculates the sum x of the value of the variable min_x divided by 2 and the value of the variable max_x divided by 2.

[0066] In addition, the provisional reliability level CLx obtained by substituting the initial value of the variable min_x into x in the formula (2) described later needs to be smaller than the target reliability level CL S Similarly, the provisional reliability level CLx obtained by substituting the initial value of the variable max_x into x in the formula (2) described later needs to be greater than the target reliability level CL S .

[0067] Therefore, for example, the initial value of the variable min_x may be set to 0, and the initial value of the variable max_x may be set to the maximum valid value of the numeric type used for calculation.

[0068] The average value calculation unit 31 performs rounding processing of rounding down the numerical value of the lower digit of each value so that each value of min_x / 2, max_x / 2, and x falls within the maximum number of significant digits of the numerical type used. That is, min_x / 2, max_x / 2, and x calculated by the average value calculation unit 31 include rounding errors. In addition, the above rounding processing is not limited to rounding down, and it can also be any rounding processing such as rounding up.

[0069] The numerical type of the variables min_x, max_x, and x is, for example, any one of single-precision floating point numbers (float type), double-precision floating point numbers (double type), or fixed-point numbers. The double type is 64-bit data consisting of 1-bit sign bit, 52-bit valid bits, and 11-bit exponent bits. The maximum valid value of the double type is 1.79769313486232E+308 in decimal conversion.

[0070] The provisional reliability level calculation unit 32 calculates the provisional reliability level CLx by substituting the sum x calculated by the average value calculation unit 31 into the following formula (2). As can be seen from the formula (2), the provisional reliability level CLx increases monotonically with respect to the sum x.

[0071] [Formula 4]

[0072]

[0073] In addition, in formula (2),

[0074] x: N×ER S ;

[0075] N: data transmission rate [data / s] × measurement time [s];

[0076] ER S : Target bit error rate (Error Rate: ER);

[0077] E: The number of assumed errors.

[0078] That is, formula (2) is the N×BER of formula (1) S Replace with N×ER S (=x).

[0079] The data transmission rate is a parameter indicating the number of measurement units included in the input signal from DUT200 per second. The measurement unit is, for example, 1 bit, 1 symbol (PAM4 Symbol), 1 Flit (Flit: Flow Control Unit), or 1 Codeword. Therefore, N is a parameter indicating the number of measurement units included in the input signal from DUT200 within the measurement time, that is, the number of measurement data. Target bit error rate ER S For example, it is any one of BER, SER, Uncorrectable Codeword Rate, or Flit Error Rate, which is an upper limit value that can be allowed as the bit error rate of the input signal.

[0080] When the provisional reliability level CLx calculated by the provisional reliability level calculation unit 32 is equal to the target reliability level CL S If the interim reliability level CLx calculated by the interim reliability level calculation unit 32 is greater than the target reliability level CLx, the upper and lower limit value update unit 33 substitutes the latest sum x into the variable min_x. S When , the upper and lower limit value updating unit 33 substitutes the latest sum x into the variable max_x.

[0081] The provisional reliability level CLx increases monotonically with respect to the sum x. Therefore, by repeating the processing by the average value calculation unit 31, the provisional reliability level calculation unit 32, and the upper and lower limit value update unit 33, the range of the value of the sum x can be narrowed and the approximate value of the sum x can be obtained. Figure 3 1 and 2 are diagrams for explaining the process of narrowing down the sum x by the average value calculation unit 31 , the provisional reliability level calculation unit 32 , and the upper and lower limit value update unit 33 .

[0082] First, the average value calculation unit 31 calculates the sum x using the initial value of the variable min_x and the initial value of the variable max_x (step S1 ).

[0083] Next, the provisional reliability level calculation unit 32 substitutes the sum x calculated in step S1 into equation (2) to calculate the provisional reliability level CLx. When the provisional reliability level CLx calculated by the provisional reliability level calculation unit 32 is greater than the target reliability level CL S When the upper and lower limit value update unit 33 substitutes the latest sum x into the variable max_x. The average value calculation unit 31 calculates the sum x again using the initial value of the variable min_x and the updated variable max_x (step S2).

[0084] Next, the provisional reliability level calculation unit 32 substitutes the sum x calculated in step S2 into equation (2) to calculate the provisional reliability level CLx. When the provisional reliability level CLx calculated by the provisional reliability level calculation unit 32 is equal to the target reliability level CL S When the upper and lower limit value update unit 33 substitutes the latest sum x into the variable min_x, the average value calculation unit 31 calculates the sum x again using the updated variable min_x and variable max_x (step S3).

[0085] Next, the provisional reliability level calculation unit 32 substitutes the sum x calculated in step S3 into equation (2) to calculate the provisional reliability level CLx. When the provisional reliability level CLx calculated by the provisional reliability level calculation unit 32 is greater than the target reliability level CL S When the upper and lower limit value update unit 33 substitutes the latest sum x into the variable max_x, the average value calculation unit 31 calculates the sum x again using the variable min_x and the updated variable max_x (step S4).

[0086] That is, the average value calculation unit 31 calculates the latest sum x using the latest variable min_x and the latest variable max_x. Furthermore, the provisional reliability level calculation unit 32 substitutes the latest sum x into the formula (2) to calculate the provisional reliability level CLx. Then, the upper and lower limit value update unit 33 substitutes the latest sum x into the variable min_x or the variable max_x according to the latest provisional reliability level CLx. In this way, the processing unit 30 repeats the narrowing process of the sum x performed by the average value calculation unit 31, the provisional reliability level calculation unit 32, and the upper and lower limit value update unit 33 using the latest variable min_x and the latest variable max_x.

[0087] The convergence determination unit 36 ​​determines whether the change in the value of the sum x calculated by the average value calculation unit 31 converges within a predetermined range. As an example, the convergence determination unit 36 ​​may determine whether the significant figures of the sum x calculated by the average value calculation unit 31 converge to a certain value. When the numerical types of the variables min_x, max_x, and sum x are double types, the significant figures of the variables min_x, max_x, and sum x are the significant digits of the double type.

[0088] For example, when the latest sum x is equal to the previous sum x, the convergence determination unit 36 ​​determines that the significant figures of the sum x have converged to a certain value. Alternatively, when the sum x calculated by the average value calculation unit 31 is equal to any number of times three or more in a row, the convergence determination unit 36 ​​may determine that the significant figures of the sum x have converged to a certain value.

[0089] Figure 4 This is a table showing the changes in the values ​​of the variables min_x, max_x, and x when the numeric types are double types. Figure 5 It means in Figure 4 The graph of data near the point where the sum x converges is shown in the variation of the variable min_x, the variable max_x, and the sum x. Here, it is assumed that the input signal from the DUT 200 is an NRZ signal, and the data transmission rate is assumed to be 2.4 Gbps. The target bit error rate ER, which is the basis of the reliability level, is S is 1E-14, the assumed error number E, which is the basis of the reliability level, is 3, and the target reliability level is CL S It is 0.98.

[0090] exist Figure 4 In the example, it can be seen that the value of min_x changes in the 1071st and 1072nd calculation results, but the value of x does not change. This means that the value of x has converged due to round-off error.

[0091] In addition, in the calculation results of the 1069th to 1072nd times, CL S is consistent with CLx, but sometimes, depending on the input value of equation (2), x is in CLS It converges before it is consistent with CLx. Therefore, it is not desirable to S Whether or not the sum x is consistent with CLx is used as the end determination condition of the narrowing process of sum x.

[0092] When double type is used as the numeric type of the variable min_x, the variable max_x, and the sum x, a result with about 14 significant digits can be obtained in decimal conversion. The number of repetitions of the sum x narrowing process is about 1000 times, and the time required for 1000 repetitions is about tens of milliseconds. Therefore, it is considered that the sum x narrowing process does not impair the convenience of the user.

[0093] Furthermore, in the narrowing process, the convergence of the sum x based on the rounding error is used as the end determination condition of the process, not the number of repetitions of the process. Therefore, the user does not need to consider the range of the value of the sum x or the number of repetitions of the process every time the various measurement conditions are changed on the setting screen 50.

[0094] Alternatively, the convergence determination unit 36 ​​may determine whether the change in the value of the sum x calculated by the average value calculation unit 31 is less than a predetermined value of the number of digits less than the maximum number of significant digits of the numerical type used, rather than waiting for the convergence of the sum x due to the rounding error. In this case, although the number of significant digits is reduced, the range reduction process can be further accelerated.

[0095] The transmission speed conversion unit 37 converts the baud rate input to the setting screen 50 described later into a transmission speed (data transfer rate) corresponding to the measurement unit.

[0096] As shown in the following equation (3), the measurement time calculation unit 38 calculates the sum x calculated by the average value calculation unit 31 and determined to be converged by the convergence determination unit 36, divided by the data transmission rate converted by the transmission speed conversion unit 37 and the target bit error rate ER S The product value of is used as the measurement time.

[0097] Measurement time [s] = x / (data transmission rate [data / s] × ER S )……(3)

[0098] The operation unit 41 is used to accept the user's operation input. Figure 1 The bit error rate measurement device 1 shown in the figure is provided with a user interface such as an operation knob, various keys, switches, buttons, or soft keys on the display screen of the display unit 42. The operation unit 41 performs various settings related to the bit error rate measurement of the bit error rate measurement device 1 or various measurement conditions on the setting screen 50.

[0099] The display unit 42 is composed of Figure 1The bit error rate measurement device 1 shown in the figure is provided with a display device such as an LCD (Liquid Crystal Display) or a CRT (Cathode Ray Tube), and displays a setting screen 50 or measurement results, etc., according to a display control signal from a control unit 43. In addition, the display unit 42 may have the operation functions of the operation unit 41 such as soft keys on the display screen.

[0100] The control unit 43 centrally controls the signal output unit 10, the signal input unit 20, the data storage unit 40, the operation unit 41, and the display unit 42. The control unit 43 is composed of a control device such as a computer including a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an FPGA (Field Programmable Gate Array), a ROM (Read Only Memory), a RAM, a HDD (Hard Disk Drive), etc. The control unit 43 can constitute at least a part of the bit error rate measurement unit 22 by software by executing a predetermined program by the CPU or the GPU.

[0101] like Figure 6 As shown, the display unit 42 displays a setting screen 50 for setting the measurement conditions related to the bit error rate of the input signal from the DUT 200 .

[0102] The setting screen 50 includes a drop-down menu 52 of "Target", text boxes 53a and 53b of "ER", a text box 54 of "EC", text 55 indicating the unit of the assumed error number E, a drop-down menu 56 of "Cycle", a drop-down menu 57 of "Unit", text boxes 58a and 58b of measurement time, a text box 59 of "Baud Rate" and a text box 60 of "Confidence Level" in the display area 51 ("Gating" in the figure).

[0103] The drop-down menu 52 of "Target" constitutes a measurement unit input unit for inputting a measurement unit of a bit error rate. The drop-down menu 52 of "Target" can select, for example, any one of the measurement units of "Bit", "PAM4Symbol", "Flit", or "Codeword". The measurement unit input unit and the baud rate input unit described later constitute a transmission speed input unit for inputting a transmission speed of an input signal from the DUT 200.

[0104] Figure 7This is a table showing the measurement units selectable in the pull-down menu 52 of “Target” and the data transmission rate of each measurement unit converted by the transmission rate conversion unit 37 .

[0105] "Bit" is a measurement unit selected when it is desired to measure the BER of the input signal from the DUT 200. When the input signal from the DUT 200 is an NRZ signal, the transmission speed conversion unit 37 directly outputs the baud rate input to the text box 59 of "Baud Rate" described later as the data transmission rate. When the input signal from the DUT 200 is a PAM4 signal, the transmission speed conversion unit 37 outputs a rate obtained by doubling the baud rate input to the text box 59 of "Baud Rate" as the data transmission rate.

[0106] "PAM4 Symbol" is a measurement unit selected when it is desired to measure the SER of the input signal from the DUT 200. When the input signal from the DUT 200 is a PAM4 signal, the transmission speed conversion unit 37 directly outputs the baud rate input to the "Baud Rate" text box 59 as the data transmission rate.

[0107] "Flit" is a measurement unit selected when it is desired to measure the Flit Error Rate of the input signal from the DUT 200. The transmission speed conversion unit 37 outputs the data transmission rate as a rate obtained by doubling the baud rate input to the "Baud Rate" text box 59 and dividing it by the Flit length. Here, the Flit length is 2048 bits.

[0108] "Codeword" is a measurement unit selected when it is desired to measure the Uncorrectable Codeword Rate of the input signal from the DUT 200. The transmission speed conversion unit 37 outputs a rate obtained by doubling the baud rate input to the "Baud Rate" text box 59 and dividing it by the CW (Codeword) length as the data transmission rate. Here, in the case of RS-FEC (Reed-Solomon Forward Error Correction) (544, 514) specified in IEEE802.3, the CW length is 5440 bits.

[0109] The text boxes 53a and 53b of "ER" are used to input the desired target error rate ER of the input signal from the DUT 200. S The target bit error rate input section. The target bit error rate ER can be input in the text boxes 53a and 53b using index notation. S, enter the significant digits in the text box 53a, and enter the exponent digits in the text box 53b. For example, values ​​within the range of 1E-3 to 1E-15 can be entered in the text boxes 53a and 53b.

[0110] The text box 54 of "EC" constitutes an assumed error number input section for inputting the assumed error number E within the measurement time of the input signal from the DUT 200. For example, a value in the range of 0 to 10 can be input in the text box 54. In addition, the display of the text 55 indicating the unit of the assumed error number E input in the text box 54 changes according to the measurement unit selected in the pull-down menu 52 of "Target".

[0111] For example, when "Bit" is selected in the "Target" pull-down menu 52, the text 55 is displayed as "Bit". When "PAM4 Symbol" is selected in the "Target" pull-down menu 52, the text 55 is displayed as "Symbol". When "Flit" is selected in the "Target" pull-down menu 52, the text 55 is displayed as "Flit". When "Codeword" is selected in the "Target" pull-down menu 52, the text 55 is displayed as "Codeword".

[0112] The pull-down menu 56 of “Cycle” allows selection of any measurement action among, for example, “Repeat (CL): Repeat (CL)”, “Single (CL): Once (CL)”, “Repeat”, “Single”, or “Untimed: Untimed”.

[0113] “Repeat (CL)” is a measurement action for repeating the bit error rate measurement for the measurement time calculated by the measurement time calculation unit 38. “Single (CL)” is a measurement action for performing the bit error rate measurement for the measurement time calculated by the measurement time calculation unit 38 once. “Repeat” is a measurement action for repeating the bit error rate measurement for the measurement time corresponding to the measurement cycle selected in the “Unit” pull-down menu 57 described later. “Single” is a measurement action for performing the bit error rate measurement for the measurement time corresponding to the measurement cycle selected in the “Unit” pull-down menu 57 once. “Untimed” is a measurement action for continuing the bit error rate measurement from the measurement start instruction of pressing the measurement start button (not shown) to the measurement end instruction of pressing the measurement stop button (not shown).

[0114] The "Unit" drop-down menu 57 allows selection of a measurement cycle unit, for example, "Time", "Clock Count" or "Error Count". In addition, when "Repeat (CL)" or "Single (CL)" is selected in the "Cycle" drop-down menu 56, the "Unit" drop-down menu 57 is fixed to "Time".

[0115] "Time" is an item for inputting or displaying the measurement time as a unit of the measurement cycle in the measurement time text boxes 58a and 58b. When "Repeat" or "Single" is selected in the "Cycle" pull-down menu 56, the measurement time text boxes 58a and 58b can input the measurement time equivalent to one measurement cycle in units of 1 second within the range of 1 second to 99 days, 23 hours, 59 minutes and 59 seconds. In the text box 58a, for example, the number of days within the range of 0 days to 99 days can be input. And, in the text box 58b, for example, the time within the range of 1 second to 23 hours, 59 minutes and 59.9 seconds can be input.

[0116] When "Repeat (CL)", "Single (CL)" or "Untimed" is selected in the pull-down menu 56 of "Cycle", a value cannot be input in the text boxes 58a and 58b of the measurement time.

[0117] The text boxes 58a and 58b of the measurement time constitute a measurement time display unit that displays the measurement time calculated by the measurement time calculation unit 38 when "Repeat (CL)" or "Single (CL)" is selected in the pull-down menu 56 of "Cycle". The text box 58a can display the number of days in the range of 0 days to 99 days, for example. And the text box 58b can display the time in the range of 1 second to 23 hours, 59 minutes and 59.9 seconds, for example.

[0118] When any of the selection content of the "Target" drop-down menu 52, the input content of the "ER" text boxes 53a, 53b, the input content of the "EC" text box 54, the input content of the "Baud Rate" text box 59, or the input content of the "Confidence Level" text box 60 is changed, the display of the calculation results of the measurement time in the measurement time text boxes 58a, 58b is also automatically updated.

[0119] Here, regarding the number of seconds in the measurement time calculated by the measurement time calculation unit 38, the text box 58b displays, for example, a value rounded up at the first or second decimal place. Figure 4In the example, the value of the sum x of the 1071st and 1072nd times is 9.08411538241318E+00. At this time, the measurement time calculated by equation (3) becomes 3.78504807600549E+05 [s]. At this time, the number of days "4" is displayed in the text box 58a, and the time "09:08:24.9" (rounded up to the second decimal place) or "09:08:25" (rounded up to the first decimal place) is displayed in the text box 58b.

[0120] "Clock Count" is an item for setting the unit of the measurement cycle in clock counts in the measurement time text boxes 58a and 58b when "Repeat" or "Single" is selected in the "Cycle" pull-down menu 56. That is, when a time equal to or greater than the clock count set in the measurement time text boxes 58a and 58b has passed, the bit error rate measurement ends.

[0121] "Error Count" is an item for setting the unit of the measurement cycle in the text boxes 58a and 58b of the measurement time by the number of errors detected by the bit error rate measurement unit 22 when "Repeat" or "Single" is selected in the pull-down menu 56 of "Cycle". That is, when the bit error rate measurement unit 22 detects the number of errors set in the text boxes 58a and 58b of the measurement time, the bit error rate measurement ends.

[0122] The "Baud Rate" text box 59 constitutes a baud rate input section for inputting the transmission speed of the input signal from the DUT 200 in baud rate. The "Baud Rate" is an item for enabling the transmission speed of the input signal from the DUT 200 to be input in a range of 2.4 GBaud to 64.2 GBaud in 1 kBaud steps, for example.

[0123] The text box 60 of "Confidence Level" is used to input a desired target confidence level CL when "Repeat (CL)" or "Single (CL)" is selected in the pull-down menu 56 of "Cycle". S The target reliability level CL S The case where the reliability level reaches 0% is when the measurement time is 0 seconds or when E in equation (2) becomes infinite, which is actually impossible. S The case where the value reaches 100% is when the measurement time becomes infinite, which is actually impossible. Therefore, the values ​​of 0% and 100% cannot be set in the text box 60 .

[0124] For example, when 0% is input in the text box 60, the display unit 42 automatically switches the input value in the text box 60 to 0.1%. Also, when 100% is input in the text box 60, the display unit 42 automatically switches the input value in the text box 60 to 99.9%. Alternatively, when 0% or 100% is input in the text box 60, the display unit 42 may display an error dialog box to prompt the user to input a target reliability level CL in the range of 0.1% to 99.9%. S .

[0125] Furthermore, when "Repeat" or "Single" is selected in the pull-down menu 56 of "Cycle", the text box 60 of "Confidence Level" can display the value rounded to the second decimal place of the reliability level CL calculated by the following formula (4) in the processing unit 30 within the range of 0% to 100% in 0.1% steps. When "Repeat" or "Single" is selected in the pull-down menu 56 of "Cycle", a value cannot be input in the text box 60 of "Confidence Level".

[0126] [Formula 5]

[0127]

[0128] When "Untimed" is selected in the pull-down menu 56 of "Cycle", the display related to "Confidence Level" disappears from the setting screen 50. Also, when an item other than "Time" is selected in the pull-down menu 57 of "Unit", the display related to "Confidence Level" disappears from the setting screen 50.

[0129] The following is a method for measuring a bit error rate using the bit error rate measurement device 1 according to the present embodiment. Figure 8 An example of the processing is described in the flowchart of FIG. In addition, the description overlapping with the description of the structure of the above-mentioned bit error rate measurement device 1 is appropriately omitted. Here, the processing when "Repeat (CL)" or "Single (CL)" is selected in the pull-down menu 56 of "Cycle" is described.

[0130] First, the control unit 43 displays the setting screen 50 for setting the measurement conditions of the bit error rate of the input signal from the DUT 200 on the display unit 42 (setting screen display step S21 ).

[0131] Next, the user sets the target reliability level CL via the operation unit 41. S, the unit of measurement for the bit error rate, the baud rate of the input signal (information about the data transmission rate), the target bit error rate ER of the input signal S The measurement conditions such as the assumed number of errors E within the measurement time of the input signal are input into the setting screen 50 (input step S22).

[0132] Next, the transmission speed conversion unit 37 converts the baud rate input to the "Baud Rate" text box 59 into a transmission speed (data transfer rate) corresponding to the measurement unit selected by the "Target" pull-down menu 52 (transmission speed conversion step S23).

[0133] Next, the upper and lower limit value update unit 33 sets 0 as an initial value in the variable min_x, and sets the maximum valid value of a numeric type (for example, double type) used in the calculation as an initial value in the variable max_x (step S24 ).

[0134] Next, the average value calculation unit 31 calculates the sum x of the latest value of the variable min_x divided by 2 and the latest value of the variable max_x divided by 2 (average value calculation step S25 ). The sum x includes a rounding error.

[0135] Next, the convergence determination unit 36 ​​determines whether the change in the value of the sum x calculated in the average value calculation step S25 has converged within a predetermined range (step S26). For example, in step S26, the convergence determination unit 36 ​​determines whether the significant figures of the sum x have converged to a certain value.

[0136] When the change in the value of sum x converges within the prescribed range (step S26: Yes), the processing unit 30 executes the processing from step S31 onwards. When the change in the value of sum x does not converge within the prescribed range (step S26: No), the processing unit 30 executes the processing from step S27 onwards.

[0137] That is, step S26 is a step of repeating the processing of average value calculation step S25, provisional reliability level calculation step S27 described later, lower limit value updating step S29, and upper limit value updating step S30 using the latest variable min_x and the latest variable max_x.

[0138] In step S27 , the provisional reliability level calculation unit 32 substitutes the sum x calculated in the average value calculation step S25 into equation (2) to calculate the provisional reliability level CLx (provisional reliability level calculation step S27 ).

[0139] Next, the processing unit 30 determines whether the provisional reliability level CLx calculated in the provisional reliability level calculation step S27 is the target reliability level CL S Next (step S28).

[0140] When the provisional reliability level CLx is the target reliability level CL S If so (step S28: Yes), the upper and lower limit value update unit 33 substitutes the latest sum x into the variable min_x (lower limit value update step S29). Then, the average value calculation unit 31 calculates the sum x again in step S25 using the variable min_x updated in step S29.

[0141] When the provisional reliability level CLx is greater than the target reliability level CL S (step S28: No), the upper and lower limit value update unit 33 substitutes the latest sum x into the variable max_x (upper limit value update step S30). Then, the average value calculation unit 31 uses the variable max_x updated in step S30 to calculate the sum x again in step S25.

[0142] In step S31, the measurement time calculation unit 38 calculates the sum x determined to have converged in step S26, the data transmission rate converted in the transmission rate conversion step S23, and the target bit error rate ER input in the input step S22. S Substitute into formula (3) to calculate the target reliability level CL S The measurement time (measurement time calculation step S31).

[0143] Next, the display unit 42 displays the measurement time calculated in the measurement time calculation step S31 in the text boxes 58a and 58b (measurement time display step S32).

[0144] Next, the processing unit 30 sets the information of the measurement time displayed in the measurement time display step S32 in the bit error rate calculation unit 25 (step S33).

[0145] Next, the bit error rate calculation unit 25 calculates the bit error rate of the input signal from the DUT 200 within the measurement time set by the processing unit 30 in step S33 (bit error rate calculation step S34).

[0146] As described above, the bit error rate measurement device 1 according to the present embodiment can calculate the desired target reliability level CL by performing the narrowing process of x in the bit error rate measurement of the input signal. S The measurement time is calculated without the user being aware of the measurement time calculation process.

[0147] Furthermore, the bit error rate measurement device 1 according to the present embodiment sets the convergence based on the rounding error as the end judgment condition for the narrowing range processing of the sum x, thereby being able to omit the user's labor and time of considering the range of values ​​to be considered as the sum x or the number of repetitions of the processing each time various measurement conditions are changed on the setting screen 50.

[0148] Furthermore, when the numerical types of the variable min_x, the variable max_x, and the sum x are double types, the bit error rate measurement device 1 according to the present embodiment can calculate the measurement time using the sum x having approximately 14 significant figures in decimal conversion.

[0149] Furthermore, the bit error rate measurement device 1 according to the present embodiment can achieve a desired target reliability level CL. S The bit error rate of the input signal is calculated within the measurement time.

[0150] Explanation of symbols

[0151] 1-bit error rate measuring device, 25-bit error rate calculating unit, 30-processing unit, 31-average value calculating unit, 32-provisional reliability level calculating unit, 33-update unit for upper and lower limits, 36-convergence determination unit, 37-transmission speed conversion unit, 38-measurement time calculating unit, 41-operating unit, 42-display unit, 43-control unit, 50-setting screen, 52, 56, 57-pull-down menu, 53a, 53b, 54, 58a, 58b, 59, 60-text box, 55-text, 200-DUT.

Claims

1. A bit error rate measurement device for measuring the bit error rate of an input signal from a test object (200), the bit error rate measurement device (1) comprising a processing unit (30), the processing unit (30) calculating the measurement time that satisfies the target reliability level based on the target reliability level, the data transmission rate of the input signal, the target bit error rate of the input signal, and the assumed number of errors E within the measurement time of the input signal, The processing unit comprises: an average value calculation unit (31) for calculating a sum x of a value obtained by dividing a variable min_x by 2 and a value obtained by dividing a variable max_x by 2; A provisional reliability level calculation unit (32) substitutes the sum x into the following formula (2) to calculate a provisional reliability level CLx; an upper and lower limit value updating unit (33), which substitutes the sum x into the variable min_x when the provisional reliability level CLx is lower than the target reliability level, and substitutes the sum x into the variable max_x when the provisional reliability level CLx is greater than the target reliability level; a convergence determination unit (36) for determining whether a change in the value of the sum x calculated by the average value calculation unit converges within a predetermined range; and a measurement time calculation unit (38) that calculates, when the convergence determination unit determines that convergence has occurred, a value obtained by dividing the converged sum x by the product of the data transmission rate and the target bit error rate as the measurement time, When the convergence determination unit does not determine that convergence has occurred, the processing unit repeats the processing of the average value calculation unit, the provisional reliability level calculation unit, and the upper and lower limit value update unit using the latest variable min_x and the latest variable max_x, [Formula 1] 2. The bit error rate measurement device according to claim 1, characterized in that: The sum x calculated by the average value calculation unit includes a rounding error, When the significant figures of the sum x converge to a certain value, the measurement time calculation unit calculates a value obtained by dividing the converged sum x by a product of the data transmission rate and the target bit error rate as the measurement time.

3. The bit error rate measurement device according to claim 2, characterized in that: The sum x is double precision floating point data, The significant digits are the significant digits of a double-precision floating point number.

4. The bit error rate measurement device according to claim 1, characterized in that: Also available: A bit error rate calculation unit (25) calculates the bit error rate of the input signal within the measurement time calculated by the measurement time calculation unit.

5. A method for measuring a bit error rate, which measures the bit error rate of an input signal from a measured object (200), wherein the method for measuring a bit error rate comprises: An input step (S22) of inputting a target reliability level, a data transmission rate of the input signal, a target bit error rate of the input signal, and an assumed number of errors E within a measurement time of the input signal; Step (S24), setting initial values ​​for the variables min_x and max_x; an average value calculation step (S25), calculating the sum x of the value of the variable min_x divided by 2 and the value of the variable max_x divided by 2; A provisional reliability level calculation step (S27), substituting the sum x into the following formula (2) to calculate a provisional reliability level CLx; a lower limit value updating step (S29), when the provisional reliability level CLx is lower than the target reliability level, substituting the sum x into the variable min_x; an upper limit value updating step (S30), when the provisional reliability level CLx is greater than the target reliability level, substituting the sum x into the variable max_x; Step (S26), using the latest variable min_x and the latest variable max_x to repeat the processing of the average value calculation step, the provisional reliability level calculation step, the lower limit value update step and the upper limit value update step; and a measurement time calculation step (S31), in which, when the change in the value of the sum x calculated in the average value calculation step converges within a prescribed range, a value of the converged sum x divided by the product of the data transmission rate and the target bit error rate is calculated as the measurement time that satisfies the target reliability level, [Formula 2] 6. The bit error rate measurement method according to claim 5, characterized in that: The sum x calculated in the mean value calculation step includes rounding errors, When the significant digits of the sum x converge to a certain value, the measurement time calculation step calculates a value obtained by dividing the converged sum x by the product of the data transmission rate and the target bit error rate as the measurement time.

7. The bit error rate measurement method according to claim 6, characterized in that: The sum x is double precision floating point data, The significant digits are the significant digits of a double-precision floating point number.

8. The bit error rate measurement method according to claim 5, characterized in that: Also includes: A bit error rate calculation step (S34) is to calculate the bit error rate of the input signal within the measurement time calculated in the measurement time calculation step.

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