JP2022042837A - Error rate measuring device and error rate measuring method - Google Patents

Abstract

To provide an error rate measuring device and an error rate measuring method that can easily determine whether or not jitter measurement has been correctly performed and easily reset configuration for correct measurement when measurement has not been correctly performed.SOLUTION: An error rate measuring device 1 comprises: a parameter setting unit 7a for setting upper- and lower-limit values that define an error rate measurement range; a measurement control unit 7c for causing an error rate of a measurement signal to be measured while operating a phase relation between data inputted as signals to be measured and clock signals; a jitter measurement control unit 7e for calculating a bathtub characteristic that indicates a relation between the operated phase relation and the measured error rate and calculating a jitter value of the signal to be measured, on the basis of the bathtub characteristic; and a display control unit 7f for causing a display unit 5 to display a jitter measurement screen 71 that includes a graph that indicates the bathtub characteristic and information that indicates the upper- and lower-values represented in association with a bathtub curve.SELECTED DRAWING: Figure 2

Description

The present invention is an error rate measurement that measures jitter based on so-called bathtub characteristics and displays the measurement result, which shows the relationship between the phase relationship between the data input as the signal to be measured and the clock signal and the measured error rate. The present invention relates to an apparatus and an error rate measuring method.

With the increase in the amount of data communication by smartphones and mobile terminals, communication systems have come to handle enormous amounts of data, and the interfaces of various communication devices constituting the communication systems are becoming faster and serial transmission. In the high speed serial bus (High Speed Serial Bus) standard such as PCIe (registered trademark) (Peripheral Component Interconnect Express) adopted in such communication equipment, LTSSM (Link Training and Status State Machine: "link status management" is used. A state machine called "mechanism") manages the initialization of communication between devices and the adjustment of link speed.

Bit Error Rate (Bit Error Rate) is defined as a comparison between the number of received data in which bit errors occur and the total number of received data as one of the indicators of signal quality evaluation in the above-mentioned communication equipment whose interface speed is increasing. : BER) is known. As a general configuration of an error rate measuring device that performs BER measurement, for example, a specific pattern defined by a standard is switched at high speed from a pulse pattern generator (PPG) and output, and the specific pattern is received. A configuration is known in which a measured signal transmitted by a target (Device Under Test: DUT) is received on the error rate measuring device (ED) side to measure the bit error rate.

On the other hand, in the field of communication tests of various digital data such as pseudo-random bit sequence (PRBS) patterns, characteristics showing the relationship between the delay time at the unit interval ui and the bit error rate (BER value), so-called A technique (BER tester) for obtaining a jitter histogram from the bathtub characteristics and obtaining an estimated value of random jitter from the jitter histogram is known (for example, Patent Document 1. Paragraphs 0004, 0012, 0028 to 0035, FIG. 1, FIG. 2).

Today, even in the above-mentioned error rate measuring device, a device having a function of measuring jitter from bathtub characteristics, such as the BER tester described in Patent Document 1, has been proposed.

Japanese Patent Application Laid-Open No. 2003-324489

An error rate measuring device having a function of measuring jitter from bathtub characteristics generally manipulates the phase relationship between a clock signal (Lock) and data (Data) input as a measured signal by a variable delay device (see FIG. 3). However, it has a configuration in which the error rate is measured and the jitter is calculated. Further, in this type of error rate measuring device, for example, the measurement efficiency can be improved by designating an upper limit value and a lower limit value and limiting the measurement range of the error rate.

In recent years, even in this type of error rate measuring device, high accuracy is required for error rate measurement due to an increase in bit rate, and high accuracy measurement is required unless measurement parameters such as error rate measurement range are set correctly. It's getting harder and harder.

Under these circumstances, this type of conventional error rate measuring device accepts the error rate measurement range without limiting the upper and lower limits, and whether the error rate measurement range is too narrow. Regardless of this, it had a configuration that enabled the calculation of jitter.

For this reason, in the conventional error rate measuring device, a sufficient measurement point may not be obtained in the bathtub curve by narrowing the measurement range too much, and the bathtub measurement may be performed under such a condition. .. In this case, an uncertain jitter value is obtained, which may be displayed as it is as a jitter measurement result.

Further, in the conventional error rate measuring device, an item for setting the error rate measurement range is provided, but what is the configuration in which the jitter measurement screen for displaying the jitter measurement result displays the item at the same time as the jitter measurement result? It wasn't. Therefore, with the conventional error rate measuring device, it is difficult to visually confirm whether or not the setting for jitter measurement is correct.

The present invention has been made to solve such a conventional problem, and it is possible to easily determine whether or not the jitter measurement has been performed correctly, and if the measurement has not been performed correctly, the correct measurement can be performed. It is an object of the present invention to provide an error rate measuring device and an error rate measuring method capable of easily performing resetting for the purpose.

In order to solve the above problems, the error rate measuring device according to claim 1 of the present invention is a setting means (6) for setting an upper limit value and a lower limit value that define a measurement range of an error rate of data input as a signal to be measured. , 7a) and a phase operation for manipulating the phase relationship between the data and the clock signal by sequentially varying the delay amount of the clock signal used for the binary determination process of the data according to the input of the data. Error rate measurement in which the pattern of the data and the predetermined pattern are compared using the means (3a2, 7b) and the determination result of the binary determination accompanied by the phase operation, and the error rate is measured based on the comparison result. A bathtub characteristic showing the relationship between the phase relationship operated by the phase operating means and the error rate measured by the error rate measuring means was calculated according to the means (3b) and the measurement of the error rate. , The jitter calculation means (7e) for calculating the jitter value of the signal to be measured based on the bathtub characteristics, the graph (72a) showing the bathtub characteristics, and the bathtub curve (72a1) in the graph. The display control means (7f) for displaying the jitter measurement screen (71) including the information (72c, 72d) indicating the upper limit value and the lower limit value set by the setting means on the display unit (5). It is characterized by having.

With this configuration, the error rate measuring device according to claim 1 of the present invention is currently setting an error with reference to the information indicating the upper limit value and the lower limit value expressed in association with the bathtub curve on the graph of the jitter measurement screen. It is possible to visually confirm whether or not there are sufficient measurement points for calculating jitter within the measurement range of the rate. If there are few measurement points and it is determined that the measurement is not correct, it is possible to easily perform resetting for correct measurement.

Further, the error rate measuring device according to claim 2 of the present invention may be configured such that the display control means further displays an approximate line (72b) that approximates the bathtub curve.

With this configuration, the error rate measuring device according to claim 2 of the present invention can visually confirm the approximate line displayed along the bathtub curve, and infer whether the measurement is performed correctly from the inclination of the approximate line. It will be possible.

Further, the error rate measuring device according to claim 3 of the present invention notifies that the display control means has not performed the jitter measurement correctly when the inclination of the approximate line does not satisfy the specified condition. The notification information (73a) may be further displayed.

With this configuration, the error rate measuring device according to claim 3 of the present invention can easily determine whether or not the measurement is performed correctly based on the displayed notification information.

Further, even if the error rate measuring device according to claim 4 of the present invention is configured such that the display control means displays the broadcast information in association with the item of the jitter value calculated by the jitter calculation means. good.

With this configuration, the error rate measuring device according to claim 4 of the present invention identifies the item to which the displayed notification information is associated, and recognizes at a glance that the jitter value of the item is not the correct measured value. can do.

Further, in the error rate measuring device according to claim 5 of the present invention, the display control means displays at least one of a symbol or a character indicating that the jitter measurement has not been performed correctly as the notification information. It may be configured to be used.

With this configuration, the error rate measuring device according to claim 5 of the present invention can easily find the displayed notification information and can more easily determine whether or not the measurement is performed correctly.

Further, the error rate measuring device according to claim 6 of the present invention may be configured such that the display control means displays the broadcast information in either a specific color or a display pattern.

With this configuration, the error rate measuring device according to claim 6 of the present invention makes it easier to find the notification information by the display color and the display pattern such as lighting or blinking, and further determines whether the measurement is performed correctly. It becomes easier to do.

Further, in the error rate measuring device according to claim 7 of the present invention, the set measurement range of the error rate is narrower than the specified measurement range as the reason why the inclination of the approximate line does not satisfy the specified condition. Further, the display control means measures the error rate displayed on the jitter measurement screen when it is specified that the measurement range of the error rate is narrower than the specified measurement range. The notification message (74f) for notifying that the setting of the measurement range of the error rate is too narrow may be further displayed in association with the tool (74e) for setting the range.

With this configuration, the error rate measuring device according to claim 7 of the present invention can easily notice that it is necessary to reset the error rate to a wider measurement range by looking at the notification message, and the notification message can be obtained. Can be easily reconfigured using the tools associated with.

Further, when it is specified that the set error rate measurement range is narrower than the specified measurement range, the error rate measuring device according to claim 8 of the present invention provides an appropriate error rate measurement range as the above reason. The display control means further includes means for estimating, and even if the display control means is configured to display a reset support message (74 g) prompting to set an appropriate error rate measurement range in close proximity to the notification message. good.

With this configuration, the error rate measuring device according to claim 8 of the present invention appropriately determines the range suggested by the resetting support message by seeing the resetting support message displayed in close proximity to the notification message. It is possible to easily reset the measurement range of the error rate.

In order to solve the above problems, the error rate measuring method according to claim 9 of the present invention is a setting step (S1) for setting an upper limit value and a lower limit value that define a measurement range of an error rate of data input as a measured signal. ) And the phase operation step (phase operation) in which the delay amount of the clock signal used for the binary determination processing of the data is sequentially changed according to the input of the data to operate the phase relationship between the data and the clock signal. (S6) An error rate measurement step (S6) in which the pattern of the data is compared with the predetermined pattern using the determination result of the binary determination accompanied by the phase operation, and the error rate is measured based on the comparison result. And, in accordance with the measurement of the error rate, the bathtub characteristic showing the relationship between the phase relationship operated by the phase operation step and the error rate measured by the error rate measurement step is calculated, and the bathtub characteristic is calculated. It is set by the jitter calculation step (S9) for calculating the jitter value of the measured signal based on the above, the graph (72a) showing the bathtub characteristics, and the setting step represented in association with the bathtub curve (72a1) in the graph. It has a display control step (S10, S20) for displaying a jitter measurement screen (71) including the information (72c, 72d) indicating the upper limit value and the lower limit value, which is displayed on the display unit (5). It is characterized by.

With this configuration, the error rate measurement method according to claim 9 of the present invention is an error currently being set with reference to the information indicating the upper limit value and the lower limit value expressed in association with the bathtub curve on the graph of the jitter measurement screen. It is possible to visually confirm whether or not there are sufficient measurement points for calculating jitter within the measurement range of the rate. If there are few measurement points and it is determined that the measurement is not correct, it is possible to easily perform resetting for correct measurement.

INDUSTRIAL APPLICABILITY According to the present invention, an error rate measuring device capable of easily determining whether or not jitter measurement has been performed correctly, and can easily perform resetting for correct measurement when the measurement has not been performed correctly, and an error rate measuring device. An error rate measuring method can be provided.

It is a block diagram which shows the schematic structure of the error rate measuring apparatus which concerns on one Embodiment of this invention. It is a block diagram which shows the functional structure of the control part of the error rate measuring apparatus which concerns on one Embodiment of this invention. It is a block diagram which shows the structure of the signal receiving part in the error rate measuring apparatus of the error rate measuring apparatus which concerns on one Embodiment of this invention. It is a graph which shows an example of the bathtub characteristic obtained by the error rate measurement by the error rate measuring apparatus which concerns on one Embodiment of this invention. It is a figure which shows the jitter calculation processing image which performs only the normal data set from the data set of the plurality of bathtub characteristics in the error rate measuring apparatus which concerns on one Embodiment of this invention. It is a schematic diagram for demonstrating the random jitter RJ _rms defined by the slope of the approximate line of the bathtub curve in the bathtub characteristic shown in FIG. It is a figure which shows the relationship between the error rate (BER) and the Q (BER) value which can be set as the measurement range of the error rate at the time of jitter measurement. It is a flowchart which shows the jitter measurement control operation by the measuring apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows the display control operation of the jitter measurement screen by the measuring apparatus which concerns on one Embodiment of this invention. It is a figure which shows the display example of the jitter measurement screen by the measuring apparatus which concerns on one Embodiment of this invention. It is a figure which shows the display example of the jitter measurement screen which concerns on the modification by the measuring apparatus which concerns on one Embodiment of this invention.

Hereinafter, an embodiment of the error rate measuring device and the error rate measuring method according to the present invention will be described with reference to the drawings.

As shown in FIG. 1, the error rate measuring device 1 according to the present embodiment includes a pulse pattern generator (PPG) 2, an error rate measuring device (Error Detector: ED) 3, a storage unit 4, and a display unit. 5. It is configured to include an operation unit 6 and a control unit 7.

The error rate measuring device 1 generates a test signal having an arbitrary pulse pattern from the PPG 2 based on a predetermined measurement start operation by the operation unit 6, and the signal transmitted by the DUT 10 receiving the test signal is used as a measured signal in the ED3. It is a device that evaluates the performance of the DUT 10 by inputting to and measuring the bit error rate of the signal to be measured.

In particular, in the present embodiment, the phase relationship between the data input by the ED3 as the signal to be measured (hereinafter referred to as input data) and the clock signal used for the processing of the binary determination (determination of 1 or 0) of the input data. Has a phase operation control function that operates according to the user's operation. Further, the ED3 calculates and calculates the characteristic showing the relationship between the phase relationship (clock delay amount) between the input data operated by the phase operation control function and the clock signal and the measured error rate, that is, the bathtub characteristic. It also has a jitter calculation processing function that obtains the jitter of the input data based on the characteristics of the bathtub.

(About jitter)
Jitter is a fluctuation of a digital signal in the time axis direction. When the period of this fluctuation is a long period, specifically, when the fluctuation occurs at a modulation frequency of 10 Hz or more, it is defined as jitter. Jitter is composed of various jitter components. The above-mentioned TJ is composed of a DJ having a finite spread and an RJ having an infinite spread.

Jitter amount units include time units such as ns (nano ( ^10-9 ) seconds), ps (pico ( ^10-12 ) seconds), fs (femto ( ^10-15 ) seconds), and unit intervals (Unit). Interval: UI) is used. UI is the ratio of the amount of jitter per bit, and is calculated by the following equation (a) when the amount of jitter is Tj [ps] and the interval of 1 bit is Tbit [ps].
Jitter [UI] = Tj / Tbit ・ ・ ・ (a)

As a result, for example, in the case of a signal of 10 Gbit / s, the interval of 1 bit becomes 100 ps. If there is a jitter of 10 ps in this signal, the amount of jitter will be calculated as 0.1 UI. The bathtub characteristics and the jitter calculation process based on the bathtub characteristics will be described in detail later with reference to FIGS. 4 to 8.

The DUT10, which is the target of performance evaluation (measurement target), is composed of various devices such as flip-flop (F / F) circuits used in communication equipment and the like whose interface speed is increasing, which are mentioned in the background technology column. Has been done. The type of performance evaluation is limited to the wired system, and the DUT 10 is wiredly connected to the PPG2 and ED3 using a connection cable or the like, receives a test signal from the PPG2, and is subject to a predetermined standard as a response signal thereof. The measurement signal is sent to ED3. Examples of standards supported by DUT10 include OIF CEI-56G-VSR-PAM4, IEEE802.3bs, PCI Express Gen6, CEI (Common Electrical Interface), Ethernet (registered trademark) and the like. The DUT 10 may be configured by a device other than the above-mentioned F / F circuit or the like as long as it transmits a signal representing data consisting of a bit string.

In the configuration of the error rate measuring device 1 shown in FIG. 1, the PPG 2 has a signal transmission unit 2a configured by an integrated circuit or the like, and a data storage unit 2b configured by a memory such as a RAM.

The data storage unit 2b stores in advance reference data having a size of, for example, 128 Mbits. The signal transmission unit 2a transmits a signal representing the data read from the data storage unit 2b to the DUT 10.

The ED3 has a signal receiving unit 3a and an error rate measuring unit 3b. The signal receiving unit 3a receives the measured signal transmitted from the DUT 10 and outputs the input data of the received signal to the error rate measuring unit 3b. For example, as shown in FIG. 3, 0/1 determination is made. It has a device 3a1 and a variable delay device 3a2.

The 0/1 determination device 3a1 performs binary determination of 1 or 0 based on the clock signal given from the variable delay device 3a2 for the input data (measured signal) from the DUT 10. The variable delay device 3a2 has a phase operation function for manipulating the phase relationship between the input data and the clock signal for a predetermined phase range by sequentially changing the delay amount of the clock signal used for the binary determination process of the input data. have. Specifically, the variable delay device 3a2 inputs the clock signal, delays the clock signal based on the operation of the delay amount from the phase operation control unit 7b (see FIG. 2), and outputs the clock signal to the 0/1 determiner 3a1. do. The variable delay device 3a2, together with the phase operation control unit 7b, constitutes the phase operation means of the present invention.

With this configuration, the signal receiving unit 3a operates the clock delay amount (phase relationship between the clock signal and the data) based on the user operation, and the 0/1 determination device 3a1 of the input data is used according to the clock delay amount at that time. The operation of outputting the binary value determination result to the error rate measuring unit 3b is performed. The operation of the clock delay amount can be performed, for example, so as to move within a range of one cycle from the initial value. In the error rate measuring device 1 according to the present embodiment, measuring the error rate of the input data by moving the clock delay amount within the range of one cycle from the initial value is defined as one sweep.

In the ED3, the error rate measuring unit 3b constitutes the error rate measuring means of the present invention, and has a synchronous detection unit 3b1 and a comparison unit 3b2. The synchronization detection unit 3b1 performs a process of synchronizing the reference data (reference signal) read from the data storage unit 2b with the received input data, and if synchronization is achieved, the comparison unit 3b2 informs that fact. Notify to.

The comparison unit 3b2 is composed of, for example, an exclusive-OR circuit (EX-OR), and is a pattern of data input from the synchronization detection unit 3b1, that is, a bit of a binary determination signal of the signal to be measured by the signal reception unit 3a. By comparing each of these with the reference signal (default pattern) for each symbol (bit), a bit error in which the level of the measured signal and the level of the reference signal differ is measured. The bit comparison result of the binary signal and the reference signal for each symbol is sequentially stored in a predetermined storage area of the storage unit 4 as comparison data. Here, the error rate measuring unit 3b is configured to calculate the ratio of the bit that caused an error to the total number of symbols as the error rate based on the comparison data, and further store the calculated error rate data in the storage unit 4. You may.

The storage unit 4 also realizes a parameter setting unit 7a, a phase operation control unit 7b, a measurement control unit 7c, a bathtub characteristic calculation unit 7d, a jitter measurement control unit 7e, and a display control unit 7f, which are described later, constituting the control unit 7. The program and each of the above functional units store various information necessary for measuring the error rate of the measured signal from the DUT 10.

The display unit 5 is composed of, for example, a liquid crystal display or the like, and displays a setting screen related to BER measurement, a measurement result (jitter measurement screen, etc.), and the like.

The operation unit 6 is composed of, for example, an operation knob, various keys, switches, buttons, soft keys on the display screen of the display unit 5, and the like. The operation unit 6 has operation functions related to various operation controls such as bit error rate measurement, setting of various setting items for performing jitter measurement, instruction to start or stop measurement of DUT 10, error rate measurement, jitter measurement, and the like. ing. The operation unit 6 together with the parameter setting unit 7a constitutes the setting means of the present invention.

The control unit 7 collectively controls the PPG2, the ED3, the display unit 5, and the operation unit 6 when performing various measurements including the bit error rate (BER) using the various devices described above as the DUT 10.

As shown in FIG. 2, for example, the control unit 7 includes a parameter setting unit 7a, a phase operation control unit 7b, a measurement control unit 7c, a bathtub characteristic calculation unit 7d, a jitter measurement control unit 7e, and a display control unit 7f. ..

The parameter setting unit 7a sets various parameters for performing jitter measurement based on bathtub characteristics. As parameters of this type, the standard of the signal to be measured, the measurement range of the error rate, the phase operation pattern (clock delay amount), and the number of phase operation sweeps for calculating the error rate (1 data set of bathtub characteristics are obtained). A series of phase operations performed for this purpose is a sweep).

The phase operation control unit 7b controls the variable delay device 3a2 of the signal receiving unit 3a based on the user operation on the display unit 5, and controls (varies) the phase relationship between the input data and the clock signal. It has become.

The measurement control unit 7c generates a test signal having a pulse pattern of a standard specified by PPG2 based on the set measurement parameters, and inputs the signal transmitted by the DUT 10 receiving the test signal to the ED3 as a measured signal. Then, the error rate measurement control for measuring the bit error rate of the signal to be measured is executed, and the bathtub specific calculation unit 7d and the jitter measurement control unit 7e for the jitter measurement for measuring the jitter according to the error rate measurement are supervised. Control. In the present embodiment, the measurement control unit 7c controls the variable delay device 3a2 and the error rate measurement unit 3b, and measures the error rate of the measured signal while manipulating the phase relationship between the input data to be input and the clock signal. Controls the execution of operations.

The bathtub characteristic calculation unit 7d is a calculation function unit for calculating the bathtub characteristics showing the correspondence between the clock delay amount operated by the phase operation control unit 7b and the bit error rate measurement result by the error rate measurement unit 3b. ..

The jitter measurement control unit 7e defines an approximate line that approximates the bathtub curve portion of the bathtub characteristic based on the bathtub characteristic calculated by the bathtub characteristic calculation unit 7d, and calculates the jitter defined by the inclination of the approximate line. It has a jitter calculation processing function. The jitter measurement control unit 7e constitutes the jitter calculation means of the present invention.

The display control unit 7f controls the display unit 5 to display the measurement result of the bit error rate during the measurement operation based on the control of the measurement control unit 7c, the jitter measurement result, and various other information. In the present embodiment, the display control unit 7f has an upper limit value and a lower limit of the error rate measurement range represented in association with the graph 72a showing the bathtub characteristics calculated by the jitter measurement control unit 7e and the bathtub curve 72a1 in the graph 72a. It has a display control function for displaying a jitter measurement screen 71 (see FIG. 11) including information 72c and 72d indicating values. The display control unit 7f constitutes the display control means of the present invention.

The control unit 7 includes a CPU (Central Processing Unit), an OS (Operating System) for starting the CPU, a ROM (Read Only Memory) for storing other programs and control parameters, an OS used by the CPU for operation, and the like. It has a RAM (Random Access Memory) for storing application execution codes and data, and a non-volatile storage medium such as a hard disk device. In the control unit 7, the CPU of the parameter setting unit 7a, the phase operation control unit 7b, the measurement control unit 7c, the bathtub characteristic calculation unit 7d, the jitter measurement control unit 7e, and the display control unit 7f are stored in the ROM in the work area of the RAM. It is realized by executing a predetermined program.

In the error rate measuring device 1 having the above configuration, in the control unit 7, the bathtub characteristic calculation unit 7d calculates the bathtub characteristic of the measured signal in accordance with the measurement of the error rate of the measured signal by the error rate measuring unit 3b. , The jitter measurement control unit 7e can calculate the random jitter (Random Jitter: RJ) and the deterministic jitter (Deterministic Jitter: DJ) separately from the bathtub characteristics.

FIG. 4 shows an example of the bathtub characteristic of the signal to be measured calculated by the bathtub characteristic calculation unit 7d. In FIG. 4, the horizontal axis indicates Delay, that is, the clock delay amount (phase relationship between the clock signal and the input data), and the vertical axis indicates the error rate (BER value) by, for example, the logarithm log10 (BER).

The clock delay amount fluctuation operation (operation of moving from the left end to the right end in the figure) in FIG. 4 is performed by the extension operation control of the signal receiving unit 3a with respect to the variable delay device 3a2 by the phase operation control unit 7b. The phase operation control can finely operate (move) the phase relationship (clock delay amount) between the input data and the clock signal at intervals of, for example, one cycle. As a result, the error rate measuring unit 3b can measure the error rate corresponding to each clock phase while moving the clock delay amount to a value (clock delay amount) determined in the range of one cycle from the initial value, for example. It will be possible.

When the BER value measured by the error rate measuring unit 3b is associated with the operation of the clock delay amount (Delay) described above and represented as a graph, the clock delay amount is gradually increased from the initial value as shown in FIG. In the process, for example, the section where the BER value at each measurement point indicated by the black circle gradually decreases (first section), and then the clock delay amount is further increased to the final cycle (corresponding to one cycle). In the process of increasing the amount, a section (second section) in which the BER value at each measurement point gradually increases appears. The curve drawn by the collection of measurement points in the first section and the curve drawn by the collection of measurement points in the second section are symmetrical, and when they are combined, they form a bathtub shape. Therefore, the series of clock delay amount vs. error rate characteristics shown in FIG. 4 are generally called bathtub characteristics. The same applies to the present embodiment. Hereinafter, the curve drawn by the collection of measurement points in the first section and the curve drawn by the collection of measurement points in the second section are drawn by the first bathtub curve and the second bathtub, respectively. It shall be called a curve.

In the bathtub characteristics shown in FIG. 4, approximate lines that approximate the respective curves are drawn for both the first bathtub curve and the second bathtub curve. The approximate line of the first bathtub curve is represented by, for example, log10 (BER) = a1x + b1, and the approximate line of the first bathtub curve is represented by, for example, log10 (BER) = a2x + b2.

Further, in this bathtub characteristic, arbitrary BER values on the vertical axis are designated as BER ₀ , BER ₁ , BER _U , and BER _L , respectively. Here, BER ₀ is a reference error rate used for estimating the deterministic jitter DJ, and BER ₁ is a reference error rate used for estimating the total jitter TJ. BER ₀ and BER ₁ are predetermined.

BER _U is the upper limit of the error rate measurement range used for jitter calculation, and BER _L is the lower limit value of the error rate measurement range used for jitter calculation. BER _U and BER _L are set by the user at the time of jitter measurement (see step S1 in FIG. 8). FIG. 7 shows the relationship between the error rate (BER) and the Q (BER) value that can be set as the measurement range of the error rate in the jitter measurement.

The jitter measurement control unit 7e is configured to perform jitter calculation processing as a measurement range of an error rate defined by an upper limit value BER _U and a lower limit value BER _L set by the user. As a result, the processing load and processing time can be reduced as compared with the case where the BER measurement is performed in the range from BER ₀ to BER ₁ .

As an example of the method of calculating the random jitter RJ and the deterministic jitter DJ based on the bathtub characteristics shown in FIG. 4, a method using the following equations (1) to (4) can be mentioned.

In equation (1), NOM.INV (probability, mean, standard deviation) corresponds to the value of the inverse of the cumulative distribution function of the normal distribution. TD represents Mark Ratio, and for example, 1/2 is set as a specific value.

In the bathtub characteristics shown in FIG. 4, when BER _U and BER _L are set, the coefficients a1, b1, a2, and b2 of the above-mentioned approximation lines obtained by the least squares method are defined for the bathtub characteristics. It can be expressed by the following equations (5) and (6) using _TL and _TU in the figure.

The random jitter RJ _rms represented by the above equation (2) can be expressed by the following equation (7) by substituting the above equations (5) and (6). It can be understood from the schematic diagram of FIG. 6 that the random jitter RJ _rms can be calculated by the equation (7).

Further, by defining F, the following equation (10) can be derived from the following equation (8).

In the above equation (10), the coefficient ( ₁ / a 1-1 / a ₂ ) indicates the slope of the approximate line. From the above equation conversion, it can be seen that the random jitter RJ _rms has the following two characteristics. The first characteristic is that F (BER _L , BER _U ) is a fixed coefficient determined by the measurement conditions, and the second characteristic is the random jitter RJ _rms from the reciprocal of the slope of the two approximation lines. Is a point that can be calculated. Therefore, it can be understood that it is important to obtain the slope of the approximate line in the bathtub measurement.

Further, the deterministic jitter DJ and the total jitter TJ can be calculated by the following equations (11) and (12) using the random jitter RJ _rms .

Next, a schematic procedure for jitter measurement in the error rate measuring device 1 according to the present embodiment will be described with reference to FIG. As shown in FIG. 5, in the error rate measuring device 1 according to the present embodiment, an abnormal data set is excluded from a plurality of data sets related to bathtub characteristics obtained by sweeping a specified number of times, and only the correct data set is selected. Jitter is calculated based on the selected data set.

As a procedure for obtaining one bathtub characteristic, the error rate is measured by moving the delay within a range of one cycle from the initial value. Here, measuring the error rate by moving Delay within the range of one cycle from the initial value is defined as one sweep, and the relationship between the phase relationship and error rate of the clock signal and data obtained by one sweep is defined as a data set. do.

The bathtub characteristic calculation unit 7d can obtain a plurality of data sets by performing one sweep a plurality of times as shown in FIG. 5 in cooperation with the variable delay device 3a2 and the phase operation control unit 7b. The example of FIG. 5 shows how 5 sweeps can be performed to obtain 5 data sets. Here, the bathtub characteristic calculation unit 7d defines the NG requirement that the bathtub characteristic cannot be measured correctly, and if the obtained data set meets the NG requirement, the data set is deleted and the NG requirement is obtained. It may be configured to have a sorting function for leaving a data set that does not correspond to. In FIG. 5, when one of the six data sets obtained by performing the six sweeps is determined to be NG by the sorting function and deleted, and the jitter is calculated using the remaining five data sets. The processing image of is shown.

The jitter measurement control unit 7e has a functional configuration in which various jitters such as random jitter RJ, deterministic jitter DJ, and total jitter TJ are calculated by statistical processing using the remaining four data sets.

Next, the jitter measurement control operation in the error rate measuring device 1 will be described with reference to the flowchart shown in FIG.

In order to perform the jitter measurement process in the error rate measuring device 1, the user first operates the operation unit 6 to input the value of the desired measurement parameter, and the parameter setting unit 7a sets the measurement parameter having the input value. (Step S1). The measurement parameters to be set include the standard of the test signal, the measurement range of the error rate, the phase operation pattern of the clock signal, and the number of times the bathtub measurement is performed (the number of sweeps).

The standard of the test signal is set, for example, by selectively designating one desired pattern from the pseudo-random (Pseudo Random Binary Sequence: PRBS) patterns having various pattern lengths. The error rate measurement range is set by specifying the upper limit value (BER _U ) and the lower limit value (BER _L ). As the phase operation pattern of the clock signal, the unit phase amount to be changed, the sweep period, and the like are set. The number of sweeps for bathtub measurement is set to an arbitrary number such as 5, for example.

After the measurement parameter setting is completed, the measurement control unit 7c monitors whether or not the jitter measurement start operation instructing the start of the jitter measurement has been performed (step S2). If it is determined that the jitter measurement start operation has not been performed (NO in step S2), the measurement control unit 7c continues the monitoring (step S2).

On the other hand, when it is determined that the jitter measurement start operation has been performed (YES in step S2), the measurement control unit 7c controls the signal transmission unit 2a to transmit the test signal of the standard set in step S1. (Step S3). When the DUT 10 receives the test signal after the test signal is transmitted from the signal transmission unit 2a, the DUT 10 transmits the measured signal as the response signal.

After controlling the signal transmission unit 2a to transmit the test signal in step S3, the measurement control unit 7c transmits the measured signal (data) transmitted by the DUT 10 by receiving the test signal to 0/1 of the signal reception unit 3a. It is controlled so that the determination device 3a1 is sequentially input (step S4).

In accordance with the input of the data in step S4, the phase operation control unit 7b sets the variable delay device 3a2 of the signal receiving unit 3a to the phase operation in which the clock signal is set for the input data (input data) in step S1. Control to delay with a pattern. Specifically, the phase operation control unit 7b controls to operate the clock delay amount (Delay) so as to move in order within the range of one cycle from the initial value (step S5). By this phase operation control, the binary determination result "0" or "1" of the data is output from the 0/1 determination device 3a1 of the signal receiving unit 3a using the clock signal that has undergone the delay operation (phase operation). Then, the signal receiving unit 3a sends the above data and its binary determination result to the error rate measuring unit 3b.

Subsequently, the measurement control unit 7c controls the error rate measurement unit 3b to perform the error rate measurement process based on the binary determination result of the data input from the signal reception unit 3a (step S6). Specifically, the measurement control unit 7c controls the synchronization detection unit 3b1 so as to synchronize the data input from the signal reception unit 3a with the reference pattern (default pattern) of the test signal of the above standard given from the data storage unit 2b. do. Next, the measurement control unit 7c controls the comparison unit 3b2 to compare the binary value determination result of the data with the reference pattern and store the comparison result in the BER measurement result storage area of the storage unit 4. As a result, in step 6, the error rate measurement result corresponding to the fluctuation of the clock delay amount within the range of one cycle from the initial value can be obtained.

Subsequently, the measurement control unit 7c controls the bathtub characteristic calculation unit 7d to calculate the bathtub characteristic (step S7). By this control, the bathtub characteristic calculation unit 7d determines the relationship between the phase relationship between the clock signal and the data and the measured error rate based on the operation control of the clock delay amount in step S5 and the BER measurement result in step S6. The arithmetic processing for generating the data set of the bathtub characteristics shown is executed (step S7).

The processes of steps S5, S6 and S7 are the processes described with reference to FIG. 5, that is, the measurement process of measuring the error rate by moving the clock delay amount (Delay) within the range of one cycle from the initial value (1 time). 1 Sweep) Corresponds to the process of performing and acquiring the data set of bathtub characteristics (data set related to 1 sweep). In the present embodiment, the measurement control unit 7c performs the above sweeps a plurality of times (the default number of sweeps set in step S1), and generates a predetermined number of data sets corresponding to each sweep. The signal receiving unit 3a, the error rate measuring unit 3b, and the bathtub characteristic calculating unit 7d are controlled.

In order to perform the above-mentioned multiple sweeps, the measurement control unit 7c generates a data set of bathtub characteristics by one sweep in step S7, and then determines whether or not the number of sweeps has reached the specified number (step S8). .. If it is determined that the number of sweeps has not reached the specified number (NO in step S8), the processes from step S3 to step S8 are repeatedly executed.

If it is determined that the number of sweeps has reached the specified number during the repeated execution of the above process (YES in step S8), the measurement control unit 7c instructs the jitter measurement control unit 7e to calculate the jitter. Based on the above instruction, the jitter measurement control unit 7e performs a jitter calculation process based on a plurality of data sets (each of which is a data set related to one sweep) obtained so far (step S9). By this arithmetic processing, the jitter measurement control unit 7e finally has the jitter values of random jitter RJ, deterministic jitter DJ, and total jitter TJ based on the above equations (10), (11), and (12), respectively. Is calculated.

During the series of jitter measurement processing from step S1 to step S9 described above, the display control unit 7f displays, for example, the jitter measurement screen 71 having the configuration shown in FIG. 10 based on the processing results in each processing step. Is controlled to be displayed in (step S10).

Next, the display control operation of the jitter measurement screen by the display control unit 7f will be described with reference to the flowchart shown in FIG.

When this display control is started, the display control unit 7f acquires the measurement range of the error rate set in step S1 of the jitter measurement process shown in FIG. 8 (step S11).

Next, the display control unit 7f acquires a data set of bathtub characteristics generated in successive steps S7 by each of the above sweeps during the jitter measurement process shown in FIG. 8 (step S12), and further, during the jitter measurement process shown in FIG. The jitter measurement result in step S9 of the above is acquired (step S13).

Subsequently, the display control unit 7f generates image data corresponding to the base screen of the jitter measurement screen 71 based on each data of the error rate measurement range, the bathtub characteristic data set, and the jitter measurement result acquired in steps S11 to S13. (Step S14). In the base screen generated here, for example, on the jitter measurement screen 71 shown in FIG. 10, the approximate line 72b of the bathtub curve in the bathtub characteristics, the horizontal lines 72c and 72d indicating the measurement range of the error rate, and the jitter measurement could not be performed correctly. Image content when the notification message 74f for notifying the cause (reason) is not provided and the display mode for notifying that the jitter measurement could not be performed correctly (the state in which the notification information 73a is not displayed) is not set. It has. In the following, the screen displayed based on the base screen may be referred to as a jitter measurement screen 70.

After generating the base screen, the display control unit 7f targets the bathtub characteristic display area 72 on the base screen based on both the error rate measurement range acquired in step S11 and the bathtub characteristic data acquired in step S12. Image processing is performed to add images of the horizontal lines 72c and 72d indicating the measurement range of the error rate and the approximate line 72b of the bathtub curve, respectively (step S15). The horizontal lines 72c and 72d correspond to the information indicating the upper limit value and the information indicating the lower limit value of the present invention, respectively.

Next, the display control unit 7f determines whether or not the approximate line 72b is normally drawn during the image processing in step S15 (step S16). This process can be determined, for example, by determining the slope of the approximate line 72b and then determining whether the slope exceeds or exceeds a preset range of values.

If it is determined that the approximation line 72b is normally closed (YES in step S16), the display control unit 7f causes the display unit 5 to display the jitter measurement screen 70 based on the image data generated in step S15 (step S20). ).

On the other hand, when it was determined that the approximate line 72b could not be drawn normally (NO in step S16), the display control unit 7f caused the reason (cause) that the approximate line 72b could not be drawn normally and the cause thereof. Specify the setting item (step S17). Here, the display control unit 7f is a tool 74e (FIG. 7) showing, for example, that the range of the error rate set is too narrow as the cause described above, and the setting status of the measurement range of the error rate as the setting item that caused the cause. It has a functional configuration that can identify each of them (see 10).

After identifying the reason (cause) that the approximation line 72b could not be drawn normally in step S17 and the setting item that caused the cause, the display control unit 7f sets the image data generated in step S15 to the step described later. The image processing of S18 and S19 is executed.

In step S18, the display control unit 7f uses image data of the notification information 73a (see FIG. 10) for notifying that the reason why the approximation line 72b could not be drawn normally is that the range of the error rate is too narrow. Performs image processing to be added to.

Next, in step S19, the display control unit 7f adds an image to the image data to display the reason why the approximation line 72b could not be drawn normally according to the setting item that caused the reason. I do. Specifically, the display control unit 7f displays the setting item that caused the reason that the error rate range is too narrow, for example, the setting status of the error rate measurement range. An image to be displayed corresponding to the tool 74e (see FIG. 10) is added to the image data.

Further, the display control unit 7f causes the display unit 5 to display the jitter measurement screen 71 (see FIG. 10) based on the image data processed in steps S18 and S19 (step S20). After displaying the jitter measurement screen 71 (see FIG. 101) or the jitter measurement screen 70 in step S20, the display control unit 7f displays the display screen by receiving an instruction to end the display from the operation unit 6. Stops and ends a series of display processing.

Next, a display example of the jitter measurement screen 71 based on the display control shown in FIG. 9 will be described with reference to FIG.

As shown in FIG. 10, the jitter measurement screen 71 has a bathtub measurement display area 72, a jitter measurement display area 73, and a measurement status display area 74. The bathtub measurement display area 72 has, for example, a graph display area in which the error rate is scaled on the vertical axis and the clock delay amount is scaled on the horizontal axis. The jitter measurement display area 73 shows the jitter measurement results for each item such as Opt Phase, Opt BER, TJ (E-12), DJ, RJ, J2 (2.5E-3), and J9 (2.5E-10). It has a configuration to be displayed with. The measurement status display area 74 includes tools 74a, 74b, 74c, 74d, and 74e for displaying the jitter measurement status for each item. The tools 74a, 74b, 74c, 74d, and 74e check the jitter measurement status of each item of Threshold (0.000V) [Unit: V], Phase Unit, Phase Resolution [Unit: mUI], Jitter Calculation, and Calculation Error Threshold, respectively. It is designed to be displayed.

Based on the image processing in step S14 of FIG. 9, the display control unit 7f displays the graph 72a showing the bathtub characteristics with respect to the bathtub measurement display area 72 of the jitter measurement screen 71 shown in FIG. Further, the display control unit 7f displays an approximate line 72b of the bathtub curve in the bathtub characteristics on the graph 72a based on the image processing in step S15 of FIG. The approximation line 72b may or may not be drawn correctly depending on the accuracy of the acquired bathtub characteristics. The case where it can be drawn correctly is the case where the slope of the approximate line 72b is within the range of the preset slope. In FIG. 10, an example is given in which the approximate line of the second bathtub curve on the right side exceeds a preset inclination and the approximate line 72b is not drawn correctly.

Further, the display control unit 7f displays information indicating the measurement range of the error rate set by the user on the graph 72a displayed in the bathtub measurement display area 72 based on the processes of steps S11 and S15 of FIG. On the jitter measurement screen 71 shown in FIG. 10, the horizontal line 72c indicating the upper limit and the horizontal line 72d indicating the lower limit are displayed in the error rate measurement range, and the area between the horizontal line 72c and the horizontal line 72d is clearly indicated as the error rate measurement range. It has become. In particular, in the example of FIG. 10, the display mode in which the upper limit is set to E-5 and the lower limit is set to E-6 is shown.

Further, by the image processing in step S14 of FIG. 9, the display control unit 7f displays the jitter measurement result for each item numerically on the jitter measurement display area 73 of the jitter measurement screen 71 shown in FIG. In the example shown in FIG. 10, for example, a numerical value of 0.84 (unit: ps ms) is displayed as a measurement result of random jitter RJ. Regarding the random jitter RJ, the display control unit 7f is based on the image processing in step S18 of FIG. 9, and is a question mark in parentheses after the number indicating the measurement result? Is added and displayed in the form of "0.84 (?) Ps ms". In FIG. 11, the measurement result of "0.84 (?) Ps ms" is shown in an enlarged form outside 71 of the jitter measurement screen for convenience, and is displayed in a specific color. ..

As described above, the display control unit 7f adds a question mark as the notification information 73a for notifying that the approximation line 72b cannot be drawn normally after the number indicating the jitter measurement result on the jitter measurement screen 71. It is designed to be displayed. In the example of FIG. 11, the notification information 73a is displayed for all the items displayed in the jitter measurement display area 73. As the notification information 73a, in addition to the question mark, various mark information suggesting that the jitter measurement could not be performed normally may be displayed. Further, the notification information 73a may be characters or figures. Further, as the display form of the notification information 73a, various colors may be used, and for example, various patterns such as lighting and blinking may be used to display the notification information 73a in a more conspicuous form than the display of the normal measured value.

Further, the display control unit 7f further displays the setting status of each item related to the measurement status on the measurement status display area 74 of the jitter measurement screen 71 of FIG. 10 by the display control in step S14 of FIG. In the example shown in FIG. 10, for the Calculation Error Threshold, which is one of the items related to the measurement status, the range of E-6 to E-7 is set as the error rate range by using the tool 74e that specifies the measurement range of the error rate. Shows the display mode when it is set.

Further, the display control unit 7f corresponds to the item that caused the reason why the approximate line 72b could not be drawn normally when the approximate line 72b could not be drawn normally based on the image processing in step S19 of FIG. Control to attach and display. In the example of FIG. 10, the display control unit 7f identifies that the measurement range of the set error rate from E-6 to E-7 is too narrow, which is the cause of the jitter measurement failure (FIG. 10). (See step S17 in step 9), which is a factor that causes the cause, for example, "too narrow" indicating the reason that caused the cause in close proximity to the tool 74e in the item of Calculation Error Threshold in the measurement status display area 74. The notification message 74f "!" Is displayed.

According to the jitter measurement screen 71 having the display mode shown in FIG. 10, the user currently sets the horizontal lines 72c and 72d indicating the upper limit value and the lower limit value represented in association with the bathtub curve 72a1 on the graph 72a as a guide. It is possible to visually confirm whether or not there are sufficient measurement points for calculating jitter within the measurement range of the error rate in the medium. If there are few measurement points and it is determined that the measurement is not correct, it is possible to take measures to reset for correct measurement.

Further, according to the jitter measurement screen 71, the user can see the relationship between the bathtub curve 72a1 displayed on the graph 72a and the approximate line 72b thereof to obtain an approximate situation as to whether or not the jitter measurement has been performed normally. Can be grasped.

Further, when the notification information 73a is displayed after the numerical value of the measurement result of the item (for example, total jitter TJ) in the jitter measurement display area 73 of the jitter measurement screen 71, the user can normally measure the jitter of the item. You can clearly recognize what you couldn't do.

When the notification information 73a is displayed on the jitter measurement screen 71, the item corresponding to the item causing the cause that the jitter measurement in the measurement status display area 74 could not be performed normally (for example, the tool 74e indicating the measurement range of the error rate) is displayed. ), And the notification message 74f indicating the reason is displayed.

As a result, for example, when the notification message 74f "too narrow" is displayed in association with the tool 74e indicating the measurement range of the error rate, the user cannot normally perform the jitter measurement by seeing the notification message 74f. It can be easily understood that the cause is that the measurement range of the error rate is too narrow, and further, the measurement range of the error rate can be easily reset by using the tool 74e. At that time, the horizontal line 72c and the horizontal line 72d displayed in the bathtub measurement display area 72 make it possible to know at a glance the measurement range of the error rate currently being set, and the user can use this as a guide to set a wider range. You will be able to respond easily.

As described above, the error rate measuring device 1 according to the present embodiment includes the parameter setting unit 6 for setting the upper limit value and the lower limit value that define the measurement range of the error rate of the input data input from the DUT 10 as the measured signal, and the input. By sequentially varying the delay amount of the clock signal used in the process of determining the binary value (0 or 1) of the input data according to the input of the data, the phase relationship between the input data and the clock signal can be determined for a predetermined phase range. The input data pattern and the default pattern are compared with the variable delay device 3a2 to be operated and the phase operation control unit 7b using the determination result of the binary determination involving the operation of the phase relationship, and the error rate is calculated based on the comparison result. The phase relationship operated by the variable delay device 3a2 according to the error rate measurement unit 3b to be measured and the error rate measurement operation by the error rate measurement unit 3b, and the error rate measured by the error rate measurement unit 3b. It is shown in association with the jitter measurement control unit 7e that calculates the bathtub characteristics showing the relationship and calculates the jitter value of the signal to be measured based on the bathtub characteristics, the graph 72a showing the bathtub characteristics, and the bathtub curve 72a1 in the graph 72a. It is configured to include horizontal lines 72c and 72d indicating upper and lower limit values set by the parameter setting unit 6 and a display control unit 7f for displaying the jitter measurement screen 71 including the horizontal lines 72c and 72d on the display unit 5.

With this configuration, the error rate measuring device 1 according to the present embodiment is currently using the horizontal lines 72c and 72d indicating the upper limit value and the lower limit value represented in association with the bathtub curve 72a1 on the graph 72a of the jitter measurement screen 71 as a guide. It is possible to visually confirm whether or not there are sufficient measurement points for calculating jitter within the measurement range of the error rate during setting. If there are few measurement points and it is determined that the measurement is not correct, it is possible to easily perform resetting for correct measurement.

Further, in the error rate measuring device 1 according to the present embodiment, the display control unit 7f has a configuration for further displaying an approximation line 72b that approximates the bathtub curve 72a1. With this configuration, the error rate measuring device 1 according to the present embodiment can visually confirm the approximate line 72b displayed along the bathtub curve 72a1, and whether or not the measurement is performed correctly from the inclination of the approximate line 72b. It becomes possible to guess.

Further, in the error rate measuring device 1 according to the present embodiment, the display control unit 7f notifies the notification information 73a that the jitter measurement was not performed correctly when the inclination of the approximation line 72b does not satisfy the specified condition. Is further displayed. With this configuration, the error rate measuring device 1 according to the present embodiment can easily determine whether or not the measurement is performed correctly based on the displayed notification information 73a.

Further, in the error rate measuring device 1 according to the present embodiment, the display control unit 7f has a configuration in which the notification information 73a is displayed in association with the item of the jitter value calculated by the jitter measurement control unit 7e. With this configuration, the error rate measuring device 1 according to the present embodiment identifies an item to which the displayed notification information 73a is associated, and recognizes at a glance that the jitter value of the item is not a correct measured value. be able to.

Further, in the error rate measuring device 1 according to the present embodiment, the display control unit 7f is configured to display at least one of a symbol or a character indicating that the jitter measurement has not been performed correctly as the notification information 73a. Have.

With this configuration, the error rate measuring device 1 according to the present embodiment can easily find the displayed notification information 73a, and can more easily determine whether or not the measurement is performed correctly.

Further, in the error rate measuring device 1 according to the present embodiment, the display control unit 7f is configured to display the notification information 73a in either a specific color or a display pattern. With this configuration, the error rate measuring device 1 according to the present embodiment further makes it easier to find the notification information 73a by the display color and the display pattern such as lighting or blinking, and further determines whether the measurement is performed correctly. It will be easier.

Further, the error rate measuring device 1 according to the present embodiment specifies that the set error rate measurement range is narrower than the specified measurement range as the reason why the inclination of the approximation line 72b does not satisfy the specified condition. Further having means, the display control unit 7f is a tool for setting the error rate measurement range displayed on the jitter measurement screen 71 when it is specified that the error rate measurement range is narrower than the specified measurement range. It has a configuration for further displaying a notification message 74f in association with 74e to notify that the setting of the measurement range of the error rate is too narrow. The means for specifying the above is not limited to the display control unit 7f described above, and may be provided in another functional unit such as the jitter measurement control unit 7e.

With this configuration, the error rate measuring device 1 according to the present embodiment can easily notice that it is necessary to reset the error rate to a wider measurement range by looking at the notification message 74f, and the notification message. It can be easily reconfigured using the tool associated with 74f.

Further, the error rate measuring device 1 according to the present embodiment has the above-mentioned reason, and when it is specified that the measured range of the set error rate is narrower than the specified measurement range, the appropriate error rate that allows normal jitter measurement can be performed. The display control unit 7f further has a means for estimating the measurement range, and has a configuration in which the reset support message 74g for prompting the setting of the appropriate error rate measurement range is displayed in close proximity to the notification message 74f. is doing. The estimation means is not limited to the display control unit 7f described above, and may be provided in other functional units such as the jitter measurement control unit 7e.

With this configuration, the error rate measuring device 1 according to the present embodiment can see the resetting support message 74g further displayed in the vicinity of the notification message 74f, thereby expanding the range suggested by the resetting support message 74g. , It becomes possible to easily reset it as a measurement range of an appropriate error rate.

Further, the error rate measuring method according to the present embodiment includes a setting step (S1) for setting an upper limit value and a lower limit value that define a measurement range of the error rate of the input data input from the DUT 10 as a signal to be measured, and the input data. By sequentially varying the delay amount of the clock signal used for the binary (0 or 1) determination process of the input data according to the input, the phase relationship between the input data and the clock signal is manipulated for a predetermined phase range. The phase operation step (S5), the error rate measurement step (S6) in which the input data pattern and the default pattern are compared using the determination result of the binary determination, and the error rate is measured based on the comparison result, and the error rate. According to the measurement operation of the error rate by the measurement step, the bathtub characteristic showing the relationship between the above phase relationship operated in the phase operation step and the error rate measured in the error rate measurement step is calculated, and based on the bathtub characteristic. The upper limit value and the lower limit value set by the jitter calculation step (S9) for calculating the jitter value of the measured signal, the graph 72a showing the bathtub characteristics, and the above setting step represented in association with the bathtub curve 72a1 in the graph 72a are set. A display control step (S10, S20) for displaying the jitter measurement screen 71 including the horizontal lines 72c and 72d shown on the display unit 5 is included.

With this configuration, the error rate measurement method according to the present embodiment is currently set with reference to the horizontal lines 72c and 72d indicating the upper limit value and the lower limit value represented in association with the bathtub curve 72a1 on the graph 72a of the jitter measurement screen 71. It is possible to visually confirm whether or not there are sufficient measurement points for calculating jitter within the measurement range of the error rate in the medium. If there are few measurement points and it is determined that the measurement is not correct, it is possible to easily perform resetting for correct measurement.

(Modification example)
The error rate measuring device (identified with reference numeral 1A for convenience) according to a modification of the present invention has a jitter measuring screen having the configuration shown in FIG. 11 instead of the jitter measuring screen 71 shown in FIG. It has a display control function to display 71A. The error rate measuring device 1A has the same configuration as the error rate measuring device 1 (see FIG. 1) according to the above embodiment, and the display control unit 7f (see FIG. 2) of the control unit 7 displays the jitter measurement screen 71A. It controls the control.

As shown in FIG. 11, the basic configuration of the jitter measurement screen 71A is the same as that of the jitter measurement screen 71 (see FIG. 10), and the same portions as the jitter measurement screen 71 are designated by the same reference numerals. The jitter measurement screen 71A according to the modification is different from the jitter measurement screen 71 in that the reset support message 74g is further displayed in response to the notification message 74f displayed in the measurement status display area 74. There is.

Hereinafter, the display control of the jitter measurement screen 71A in the error rate measuring device 1A according to the modified example will be described with reference to the functional block diagrams of FIGS. 1 and 2 and the flowchart of FIG.

In the error rate measuring device 1A according to the modified example, the display control unit 7f executes display control according to the flowchart shown in FIG. In this display control, for example, when it is specified that the reason why the jitter measurement cannot be performed normally in step S18 is that the setting of the error rate measurement range is too narrow, the display control unit 7f measures the jitter in step S10. Estimate the proper error rate measurement range that can be performed normally.

After that, when the jitter measurement screen 71A is displayed in step S19, the display control unit 7f displays the notification message 74f "too narrow" in association with the tool 74e that sets the measurement range of the error rate in the measurement status display area 74. do. At that time, the display control unit 7f takes in information indicating an appropriate error rate measurement range in which the jitter measurement estimated in step S10 of FIG. 9 can be performed normally, and sets an appropriate error rate measurement range based on the information. For example, the reset support message 74g "How about E5 to E8?" Is further displayed in close proximity to the notification message 74f.

According to the jitter measurement screen 71A having the display mode shown in FIG. 11, the user can see the reset support message 74g further displayed in the vicinity of the notification message 74f of "too narrow" displayed in the measurement status display area 74. By observing, it becomes possible to easily reset the range of E5 to E8 suggested by the reset support message 74g as a measurement range of an appropriate error rate.

In the above-described embodiment and modification, the display control of the jitter measurement screen 71 (see FIG. 10) and the jitter measurement screen 71A (see FIG. 11) when the jitter measurement is performed on the NRZ signal has been described. The display control in the present invention can also be applied to the error rate measurement of a multi-valued PAM signal (PAM4 signal or the like) by a pulse amplitude modulation method.

As described above, the error rate measuring device and the error rate measuring method according to the present invention can easily determine whether or not the jitter measurement is performed correctly, and if the measurement is not performed correctly, the measurement is correct. It has the effect that it is possible to easily reset the error rate, and it is useful for an error rate measuring device that performs jitter measurement based on bathtub characteristics and an error rate measuring method in general.

1 Error rate measuring device 2 Pulse pattern generator (PPG)
3 Error rate measuring instrument (ED)
3a Signal receiver 3a2 Variable delayer (phase operating means)
3b Error rate measuring unit (error rate measuring means)
5 Display unit 6 Operation unit (setting means)
7 Control unit 7a Parameter setting unit (setting means)
7b Phase operation control unit (phase operation means)
7c Measurement control unit 7d Bathtub characteristic calculation unit 7e Jitter measurement control unit (jitter calculation means, identification means, estimation means)
7f Display control unit (display control means, identification means, estimation means)
10 DUT (subject to test)
71, 71A Jitter measurement screen 72 Bathtub measurement display area 72a Graph 72a1 Bathtub curve 72b Approximate line 72c Horizontal line (information indicating the upper limit value)
72d horizontal line (information indicating the lower limit)
73 Jitter measurement display area 73a Notification information 74 Measurement status display area 74e Tool 74f Notification message 74g Reset support message

Claims (9)

Setting means (6, 7a) for setting the upper and lower limits that define the measurement range of the error rate of the data to be input as the signal to be measured, and
Phase operation means (3a2, 7b) for performing a phase operation for operating the phase relationship between the data and the clock signal by sequentially varying the delay amount of the clock signal used for the binary determination processing of the data according to the input of the data. )When,
An error rate measuring means (3b) that compares a pattern of the data with a predetermined pattern using the determination result of the binary determination accompanied by the phase operation, and measures the error rate based on the comparison result.
Along with the measurement of the error rate, a bathtub characteristic showing the relationship between the phase relationship operated by the phase operating means and the error rate measured by the error rate measuring means was calculated, and based on the bathtub characteristic. Jitter calculation means (7e) for calculating the jitter value of the signal to be measured, and
The graph (72a) showing the bathtub characteristics and the information (72c, 72d) showing the upper limit value and the lower limit value set by the setting means represented in association with the bathtub curve (72a1) in the graph are shown. A display control means (7f) for displaying the including jitter measurement screen (71) on the display unit (5), and
An error rate measuring device comprising. The error rate measuring device according to claim 1, wherein the display control means further displays an approximate line (72b) that approximates the bathtub curve. The display control means further displays notification information (73a) for notifying that the jitter measurement has not been performed correctly when the inclination of the approximate line does not satisfy a specified condition. 2. The error rate measuring device according to 2. The error rate measuring device according to claim 3, wherein the display control means displays the broadcast information in association with an item of a jitter value calculated by the jitter calculation means. The error rate according to claim 3 or 4, wherein the display control means displays at least one of a symbol or a character indicating that the jitter measurement has not been performed correctly as the notification information. measuring device. The error rate measuring device according to any one of claims 3 to 5, wherein the display control means displays the broadcast information in either a specific color or a display pattern. The reason why the slope of the approximate line does not satisfy the specified condition is that the measurement range of the set error rate is further provided with a means for specifying that the measurement range is narrower than the specified measurement range.
When it is specified that the measurement range of the error rate is narrower than the specified measurement range, the display control means is used as a tool (74e) for setting the measurement range of the error rate displayed on the jitter measurement screen. The error rate measuring device according to any one of claims 1 to 6, further comprising displaying a notification message (74f) notifying that the setting of the error rate measuring range is too narrow. As the reason, if it is specified that the set measurement range of the error rate is narrower than the specified measurement range, there is further a means for estimating an appropriate error rate measurement range.
The error rate according to claim 7, wherein the display control means displays a reset support message (74 g) for prompting the setting of the appropriate error rate measurement range in close proximity to the notification message. measuring device. The setting step (S1) for setting the upper limit value and the lower limit value that define the measurement range of the error rate of the data to be input as the measured signal, and
A phase operation step (S5) for performing a phase operation for manipulating the phase relationship between the data and the clock signal by sequentially varying the delay amount of the clock signal used for the binary determination process of the data according to the input of the data. ,
An error rate measurement step (S6) in which the pattern of the data and the predetermined pattern are compared using the determination result of the binary determination accompanied by the phase operation, and the error rate is measured based on the comparison result.
Along with the measurement of the error rate, a bathtub characteristic showing the relationship between the phase relationship operated by the phase operation step and the error rate measured by the error rate measurement step was calculated, and based on the bathtub characteristic. The jitter calculation step (S9) for calculating the jitter value of the measured signal and
The graph (72a) showing the bathtub characteristics and the information (72c, 72d) showing the upper limit value and the lower limit value set by the setting step represented in association with the bathtub curve (72a1) in the graph are shown. A display control step (S10, S20) for displaying the including jitter measurement screen (71) on the display unit (5), and
An error rate measuring method, characterized in that it has.

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