JP6672376B2 - Error rate measuring device and parameter searching method of the device - Google Patents

Description

  The present invention relates to an error rate measuring apparatus that transmits a test signal of a known pattern to a device under test (DUT: Device Under Test), receives an output from the device under test accompanying the transmission of the test signal, and measures a bit error rate. And a parameter search method of the device.

  2. Description of the Related Art With the increase in the number of users and the spread of multimedia communication, various types of digital communication devices are required to have higher transmission capacity. A bit error rate (hereinafter, referred to as BER) is one of the indexes for evaluating the quality of a digital signal in this type of digital communication apparatus. The BER is defined as a comparison between the number of occurrences of code errors in the received data and the total number of received data, and is measured by, for example, an error rate measurement device disclosed in Patent Document 1 below.

  Conventionally, this type of error rate measuring apparatus is divided into a transmitting side and a receiving side, transmits a known pattern signal from the transmitting side to a device under test (DUT), and transmits the pattern under test (DUT) with the transmission of the pattern signal. The BER is measured by receiving the output from the receiving side on the receiving side.

  By the way, in order to measure the above-mentioned error rate, it is necessary to set a plurality of parameters to optimal values according to the measurement contents, measurement conditions, and the like. The parameters that need to be set include, for example, Data Delay that determines the time axis direction, Vth that is the reference voltage axis, and CTLE Gain for reading an attenuated signal.

  Then, the optimum value of each parameter can be set by changing each parameter at a plurality of points for each predetermined value, measuring the BER, and searching for a point at which the BER is minimized.

  Meanwhile, when setting the optimum value of each parameter described above, generally, a gradient method algorithm such as a steepest descent method may be used when searching for a point where the BER is minimized. The steepest descent method is one of algorithms of a gradient method of a continuous optimization problem that searches for a minimum value of a function only from a gradient of the function.

JP 2017-14290A

  However, when searching for a point where the BER is minimized using a gradient algorithm such as the steepest descent method, an error-free state occurs in a certain section depending on the input signal, and the slope in that section is determined. Can not be sought. For this reason, it has been difficult to apply a gradient method algorithm such as the steepest descent method that converges at high speed.

  As a result, conventionally, two points are searched for an error-free boundary from a point where an error occurs, and the center value thereof is set as the optimum value of the parameter. However, there is a problem that the time required for the search becomes longer because the width of the point to be searched becomes narrower as the error-free boundary is approached.

  Therefore, the present invention has been made in view of the above problems, and provides an error rate measurement device and a parameter search method of the device, which can apply a high-speed gradient algorithm even when an error-free section exists. It is intended to be.

In order to achieve the above object, an error rate measuring apparatus according to claim 1 of the present invention transmits a test signal to a device under test W and receives an output from the device under test accompanying the transmission of the test signal. Error rate measuring device 1 that measures the bit error rate
A parameter selection unit 11a for selecting a parameter to be set from a plurality of parameters necessary for measuring the bit error rate,
First searching means 11b for searching for a point at which the bit error rate is minimized by a steepest descent method ;
An error-free section discriminating means 11c for discriminating whether or not an error-free section exists while the first search means is searching for a point at which the bit error rate is minimum;
When the error-free section exists by the discrimination of the error-free section discriminating means, the difference between the left and right error-free boundaries of the phase searched by varying the step width of the phase from the slope by the steepest descent method is used as a phase margin, The difference between the upper and lower error-free boundaries of the threshold voltage searched by varying the step width of the threshold voltage from the slope by the steepest descent method is defined as the threshold voltage margin, and the value of the phase margin is multiplied by the value of the threshold voltage margin. and second search means 11d for calculating eye margin that is searched probe points as a maximum,
The point at which the bit error rate searched by the first search means is minimized when the search by the first search means ends without the error free section being determined by the error free section determination means is determined by Parameter optimization for setting as an optimal value of a parameter to be set and, when the error-free section exists, setting a point where the eye margin searched by the second searching means is maximum as an optimal value of the parameter to be set. Value setting means 11e.

The parameter search method of the error rate measurement device according to claim 2 transmits a test signal to the device under test W, receives an output from the device under test accompanying the transmission of the test signal, and determines a bit error rate. A parameter search method of the error rate measurement device 1 for measuring,
Selecting a parameter to be set from a plurality of parameters required to measure the bit error rate,
Searching for a point at which the bit error rate is minimized by a steepest descent method ;
Determining whether there is an error-free section during the search for the point where the bit error rate is minimized,
When the error-free section exists, the difference between the left and right error-free boundaries of the phase searched by varying the step width of the phase from the slope by the steepest descent method is used as the phase margin, and the threshold voltage is calculated from the slope by the steepest descent method. A point at which an eye margin calculated by multiplying the value of the phase margin and the value of the threshold voltage margin is the maximum, and the difference between the upper and lower error-free boundaries of the threshold voltage searched by varying the step width is used as the threshold voltage margin. the method comprising the steps of probe search for,
When the search for the point where the bit error rate is minimized while the error free section does not exist is completed, setting the point where the bit error rate is minimized as an optimal value of the parameter to be set,
Setting the point at which the eye margin is maximum as the optimum value of the parameter to be set when the error-free section exists.

  According to the present invention, two different gradient algorithms, BER and eye margin, can be used when setting parameters, and a high-speed gradient algorithm is applied even when an error-free section exists. Fast and accurate parameter search can be performed.

1 is a block diagram illustrating a schematic configuration of an error rate measurement device according to the present invention. FIG. 3A is a diagram illustrating an example of a minimum value of a bit error rate, and FIG. 3B is a diagram illustrating an example of an error-free section. FIG. 4 is a diagram illustrating an example of a phase margin and a threshold voltage margin. FIG. 4 is a flowchart of a parameter search method of the error rate measurement device according to the present invention.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, the error rate measurement device 1 of the present embodiment transmits a test signal of a known pattern to a device under test W and receives an output from the device under test W accompanying the transmission of the test signal. The BER (bit error rate) is measured, and includes a pattern transmitting unit 2 and a pattern receiving unit 3.

  When measuring the BER of the device under test W, the pattern transmitting section 2 generates a known pattern signal (test signal) to be input to the device under test W and transmits the signal to the device under test W.

  Although not particularly shown, the pattern transmission unit 2 includes, for example, a PRBS pattern generation unit and a programmable pattern generation unit. The PRBS pattern generation unit generates a PRBS (Pseudo-random bit sequence) pattern as a test signal of a known pattern input to the device under test W. The programmable pattern generator generates a programmable pattern including an arbitrary pattern as a test signal of a known pattern to be input to the device under test W.

  The pattern receiving unit 3 receives a signal from the device under test W accompanying the transmission of the pattern signal from the pattern transmitting unit 2 to the device under test W, and includes a parameter setting unit 11, an error rate measuring unit 12, and a display unit 13. Is provided.

  The parameter setting unit 11 sets and changes parameters. The parameter setting unit 11 operates by acquiring a BER from the error rate measurement unit 12, and performs a parameter selection unit 11 a, a first search unit 11 b, an error-free section determination unit 11 c, A search means 11d and a parameter optimum value setting means 11e.

  The parameter selecting unit 11a selects a parameter to be set from a plurality of parameters necessary for measuring BER. The parameters to be selected include, for example, Data Delay for determining the direction of the time axis, Vth as a reference voltage axis, CTLE Gain for reading an attenuated signal, and filter parameters.

  The first searching means 11b uses the steepest descent method as a gradient method algorithm in which a parameter step is dynamically determined according to the gradient, and searches for a point at which the BER is minimized. The steepest descent method is one of the gradient method algorithms for a continuous optimization problem that searches for the minimum value of a function only from the gradient (first-order derivative) of the function (potential surface).

  The error-free section discriminating means 11c, for example, as shown in FIG. 2 (b) during the search for the point (for example, b in FIG. 2 (a)) where the BER is minimized by the first searching means 11b. It is determined whether or not exists.

  Note that an error-free section in the present embodiment indicates a section in which no error can be detected within a preset measurement time.

  The second search means 11d uses the steepest descent method as a gradient method algorithm in which a parameter step is dynamically determined according to the slope when an error-free section exists during the search by the first search means 11b. Find the point where is the largest.

More specifically, the second search unit 11d uses the steepest descent method to measure the phase margin in the time axis direction and the threshold voltage margin in the voltage direction in an eye diagram as shown in FIG. 3, for example. In the measurement of the phase margin, the step width of the phase is dynamically varied from the slope by the steepest descent method, and the left and right error-free boundaries are searched.The difference between the searched left error-free boundary and the right error-free boundary is calculated as the phase margin. And Also, the measurement of the threshold voltage margin, dynamically varying the step width of the threshold voltage from the slope exploring the vertical error-free boundaries by the steepest descent method, error-free boundaries searched lower and upper error-free boundary Is the threshold voltage margin. Then, the value of the eye margin is calculated by multiplying the value of the phase margin obtained by these measurements by the value of the threshold voltage margin, and a point of the eye margin at which the calculated value is maximized is searched.

  The parameter optimum value setting unit 11e determines that the error-free section determining unit 11c determines that there is no error-free section, and when the search by the first searching unit 11b ends, the first searching unit 11b executes the steepest descent method. The point at which the BER searched using the BER is minimized is set as the optimum value of the parameter.

  Further, the parameter optimum value setting unit 11e maximizes the eye margin searched by the second search unit 11d using the steepest descent method when the error-free section determination unit 11c determines that there is an error-free section. Set the point as the optimal value for the parameter.

  The error rate measurement unit 12 transmits a known pattern signal from the pattern transmission unit 2 to the device under test W in a state where the parameters required for the BER measurement are set by the parameter setting unit 11, and The output from the device under test W accompanying the transmission is received, and the transmitted known pattern signal and the received pattern signal are compared with each other to measure the BER.

  The display unit 13 includes, for example, a liquid crystal display, and displays a setting screen for each parameter related to BER measurement, displays a BER measurement result by the error rate measurement unit 12, and the like.

  Next, a parameter search method of the error rate measurement device 1 configured as described above will be described with reference to FIG.

  First, a parameter to be set is selected by the parameter selecting means 11a, and an initial value of the selected parameter is set. When the initial value of the parameter is set, the first search means 11b searches for the optimum value of the parameter that minimizes the BER using the steepest descent method (ST1). Then, the error-free section determining means 11c determines whether or not an error-free section exists during this search (ST2).

  When the error-free section determination unit 11c determines that there is no error-free section during the search by the first search unit 11b (ST2-No), it determines whether the search by the first search unit 11b is completed. (ST3).

  If the parameter optimum value setting unit 11e determines that there is no error-free section and the search by the first search unit 11b is completed (ST3-Yes), the BER is set when the search is completed without any error-free section. The point (for example, b in FIG. 2A) at which is minimized is set as the optimal value of the parameter (ST4).

  On the other hand, if the error-free section determination means 11c determines that there is an error-free section during the search by the first search means 11b (ST2-Yes), the second search means 11d switches the gradient method algorithm, The optimum value of the parameter that maximizes the eye margin is searched using the steepest descent method (ST5).

  Then, the parameter optimum value setting unit 11e sets a point at which the eye margin searched by the second searching unit 11d is maximum as an optimum value of the parameter (ST6).

  By the way, in the above-described embodiment, the case where the steepest descent method is used as the gradient method algorithm in which the parameter step is dynamically determined is described as an example. However, the present invention is not limited to this. For example, Newton method, gradient Other gradient algorithms, such as descent, can also be used.

  As described above, according to the present embodiment, when setting parameters, two different gradient method algorithms of BER and eye margin can be used, and even when an error-free section exists, a high-speed gradient method can be used. A fast and accurate parameter search can be performed by applying the algorithm. In addition, the setting value of each parameter does not fluctuate, and the accuracy of parameter search can be improved.

  The best mode of the error rate measuring device and the error rate measuring method according to the present invention has been described above, but the present invention is not limited by the description and the drawings according to this mode. That is, it goes without saying that all other forms, examples, operation techniques, and the like made by those skilled in the art based on this form are included in the scope of the present invention.

Reference Signs List 1 error rate measuring device 2 pattern transmitting unit 3 pattern receiving unit 11 parameter setting unit 11a parameter selecting unit 11b first searching unit 11c error-free section discriminating unit 11d second searching unit 11e parameter optimum value setting unit W DUT ( DUT)

Claims (2)

An error rate measuring device (1) for transmitting a test signal to a device under test (W), receiving an output from the device under test accompanying the transmission of the test signal, and measuring a bit error rate,
Parameter selecting means (11a) for selecting a parameter to be set from a plurality of parameters necessary for measuring the bit error rate;
First search means (11b) for searching for a point at which the bit error rate is minimum by a steepest descent method ;
An error-free section discriminating means (11c) for discriminating whether or not an error-free section exists while the first search means is searching for a point at which the bit error rate is minimum;
When the error-free section exists by the discrimination of the error-free section discriminating means, the difference between the left and right error-free boundaries of the phase searched by varying the step width of the phase from the slope by the steepest descent method as a phase margin, The difference between the upper and lower error-free boundaries of the threshold voltage searched by varying the step width of the threshold voltage from the slope by the steepest descent method is defined as the threshold voltage margin, and the value of the phase margin is multiplied by the value of the threshold voltage margin. second search means for calculating the eye margin is search look for points of maximum and (11d),
When the search by the first search means is completed without the error-free section being determined by the error-free section determination means, the point at which the bit error rate searched by the first search means is minimized is determined by the error search section. Parameter optimization for setting as an optimal value of a parameter to be set, and when the error-free section exists, setting a point where the eye margin searched by the second searching means is maximum as an optimal value of the parameter to be set. An error rate measuring device comprising a value setting means (11e). A parameter search method of an error rate measurement device (1) for transmitting a test signal to a device under test (W), receiving an output from the device under test accompanying the transmission of the test signal, and measuring a bit error rate. hand,
Selecting a parameter to be set from a plurality of parameters required to measure the bit error rate,
Searching for a point at which the bit error rate is minimized by a steepest descent method ;
Determining whether there is an error-free section during the search for the point where the bit error rate is minimized,
When the error-free section exists, the difference between the left and right error-free boundaries of the phase searched by varying the step width of the phase from the slope by the steepest descent method is used as the phase margin, and the threshold voltage is calculated from the slope by the steepest descent method. A point at which an eye margin calculated by multiplying the value of the phase margin and the value of the threshold voltage margin is the maximum, and the difference between the upper and lower error-free boundaries of the threshold voltage searched by varying the step width is used as the threshold voltage margin. the method comprising the steps of probe search for,
When the search for the point where the bit error rate is minimized while the error free section does not exist is completed, setting the point where the bit error rate is minimized as an optimal value of the parameter to be set,
Setting a point at which the eye margin becomes maximum as an optimal value of the parameter to be set when the error-free section exists.

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