JP6821717B2 - Error detection device and error detection method - Google Patents

Description

The present invention decodes a PAM4 signal by a quadrature pulse amplitude modulation method (PAM4 method) in which the amplitude is divided into four types for each symbol into a binary signal (NRZ signal), and makes an error based on the level measurement result of the decoded signal. The present invention relates to an error detection device and an error detection method for detecting an error.

In standards such as 100G and 400G defined by IEEE, transmission by PAM4 signal is specified instead of transmission by PAM2 (NRZ) signal so far in order to respond to ultra-high speed of bit rate.

For the PAM4 signal, for example, as shown in Patent Document 1 below, the most significant bit string signal MSB and the least significant bit string signal LSB are generated using two signal sources, and then these signals are added together to generate 0 (00). It can be generated as a quaternary signal of 1, 1 (01), 2 (10), and 3 (11).

JP-A-2018-033098

By the way, when measuring the error rate of a symbol of a PAM4 signal, the symbol error rate (SER) is also an important index, but how many errors are inserted in each of the three eye openings (Upper Eye / Middle Eye / Lower Eye). It is also an important indicator. For example, if errors are inserted intensively in Upper Eye, it is possible to reduce the error by increasing the amplitude ratio of Upper Eye or increasing the amount of emphasis added on the pattern generator side. I understand.

Therefore, it has been desired to provide a GUI capable of knowing how many errors are inserted in each of the three eye openings, including the transition state of each symbol of the PAM4 signal for each level.

Therefore, the present invention has been made in view of the above problems, and is an error detection device and an error that can know the transition state of each symbol of the PAM4 signal for each level and the error insertion state of the three eye openings. It is intended to provide a detection method.

In order to achieve the above object, the error detection device according to claim 1 of the present invention includes a PAM decoder 2 that decodes a PAM4 signal from an error detection target into a most significant bit string signal MSB and a least significant bit string signal LSB.
A level measuring unit 3 for measuring the levels of the highest-order bit string signal and the lowest-order bit string signal decoded by the PAM decoder, and
An error is detected by level comparison between the highest bit string signal and the lowest bit string signal measured by the level measuring unit and the expected value data of each of the highest bit string signal and the lowest bit string signal, and the expected value data. The error detection unit 4 that determines the transition state of each symbol of the PAM signal for each level based on the correspondence table of the error detection conditions with respect to the level of
It is characterized by including a display unit 5 that displays a list of error counts and error rates according to the transition state of each symbol of the PAM4 signal based on the determination result of the error detection unit.

The error detection device according to claim 2 is the error detection device according to claim 1.
The error detection unit 4 detects an error count for each transition level of each of the three eye openings of the PAM signal and an error rate for each eye opening from the transition state of each symbol of the PAM signal.
The display unit 5 shows a list of error counts and error rates according to the transition state of each symbol of the PAM4 signal, and the transition of each of the three eye openings of the PAM signal detected by the error detection unit. It is characterized in that a list of error counts for each level and error rates for each eye opening is selectively displayed.

The error detection method according to claim 3 includes a step of decoding a PAM4 signal from an error detection target into a most significant bit string signal MSB and a least significant bit string signal LSB.
The step of measuring the level of the decoded highest bit string signal and the lowest bit string signal, and
An error is detected by level comparison between the measured highest-order bit string signal and lowest-order bit string signal and the expected value data of each of the highest-order bit string signal and lowest-order bit string signal, and error detection with respect to the level of the expected value data. A step of determining the transition state of each symbol of the PAM signal for each level based on the condition correspondence table, and
It is characterized by including a step of displaying a list of error counts and error rates according to the transition state of each symbol of the PAM4 signal based on the result of the determination.

The error detection method according to claim 4 is the error detection method according to claim 3.
A step of detecting an error count for each transition level of each of the three eye openings of the PAM signal and an error rate for each eye opening from the transition state of each symbol of the PAM signal.
A list of error counts and error rates according to the transition state of each symbol of the PAM4 signal, an error count for each transition level of each of the three eye openings of the PAM signal, and an error rate for each eye opening. It is characterized by including a step of selectively displaying a list of.

According to the present invention, it is possible to know to which level each symbol of the PAM4 signal has transitioned, and the transition state of each symbol including the transition direction of the level. In addition, it is possible to know the insertion state of the error in each of the three eye openings.

It is a block diagram which shows the schematic structure of the error detection apparatus which concerns on this invention. It is a figure which shows an example of the internal structure of a PAM decoder. (A) is a diagram showing the relationship between the PAM4 signal, the reference voltage, and the output in the PAM decoder of FIG. 2, and (b) is a diagram showing the truth table of the PAM decoder of FIG. (A) A diagram showing a correspondence table of error detection conditions with respect to expected value data, and (b) a diagram showing a display example of a list showing error counts and error rates according to the transition state of each symbol of the PAM4 signal. is there. It is a figure which shows the list numbered in FIG. 4 (b). It is a figure which shows the display example of the list of the symbol error for each transition level of each of the three eye openings of a PAM4 signal, and the symbol error rate for each eye opening. It is a flowchart of the error detection method which concerns on this invention.

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

[About PAM4 signal]
First, the PAM4 signal targeted by the present embodiment will be described. In the PAM4 method, a bit string composed of logic "0" and "1" is modulated as a pulse signal of four voltage levels or optical power as a pulse amplitude modulated signal in which the amplitude of an information signal is encoded by a sequence of pulse signals. It is a method of transmitting.

The PAM4 signal according to the PAM4 method has four types of amplitudes for each symbol, and has four different amplitude levels L0, L1, L2, and L3 as shown in FIG. 3A, and has an overall amplitude voltage. The range is divided from the baseline (L0: 0 level) to the low voltage range H1, the medium voltage range H2, and the high voltage range H3, and the upper signal (high level) having a different magnitude of the amplitude level with respect to the baseline (L0: 0 level). The signal), the Middle signal (medium level signal), and the Lower signal (low level signal) consist of a signal having three eye pattern openings in a continuous amplitude range.

[Error detection device]
As shown in FIG. 1, the error detection device 1 of the present embodiment is roughly configured to include a PAM decoder 2, a level measurement unit 3, an error detection unit 4, and a display unit 5.

As shown in FIG. 2, the PAM decoder 2 sets the Upper signal (high level signal), Middle signal (medium level signal), and Lower signal (low level signal) of the PAM4 signal from the object to be measured (error detection target) to 0. From the 0/1 discrimination circuit 11 that discriminates 1/1 and the discrimination signal that is 0/1 discriminated by the 0/1 discrimination circuit 11, the PAM4 signal is divided into two NRZ signals, the highest bit string signal (MSB) and the lowest bit string signal (MSB). The LSB) is roughly configured with a decoding circuit 12 for decoding.

The 0/1 discriminator circuit 11 has three 0/1 discriminators (3 0/1 discriminators) for the transmission line through which the PAM4 signal from the object to be measured is transmitted, which is folded back when the PAM4 signal (test signal) is input to the object to be measured. The first 0/1 discriminator 11a, the second 0/1 discriminator 11b, and the third 0/1 discriminator 11c) are connected in parallel.

The first 0/1 discriminator 11a discriminates 0/1 of the Upper signal of the PAM4 signal by comparison with the first reference voltage Vth1. That is, as shown in FIG. 3A, the first 0/1 discriminator 11a punches out the Upper signal at the first reference voltage Vth1 and compares the Upper signal with the first reference voltage Vth1. If the signal is the first reference voltage Vth1 or more, DU = "1" is output as a discrimination signal, and if the Upper signal is not the first reference voltage Vth1 or more, DU = "0" is output as a discrimination signal.

The second 0/1 discriminator 11b discriminates 0/1 of the Middle signal of the PAM4 signal by comparison with the second reference voltage Vth2. That is, as shown in FIG. 3A, the second 0/1 discriminator 11b punches out the Middle signal at the second reference voltage Vth2, compares the Middle signal with the second reference voltage Vth2, and compares the Middle signal with the Middle. If the signal is the second reference voltage Vth2 or more, DM = "1" is output as a discrimination signal, and if the Middle signal is not the second reference voltage Vth2 or more, DM = "0" is output as a discrimination signal.

The third 0/1 discriminator 11c discriminates 0/1 of the Lower signal of the PAM4 signal by comparison with the third reference voltage Vth3. That is, as shown in FIG. 3A, the third 0/1 discriminator 11c punches out the Lower signal at the third reference voltage Vth3, compares the Lower signal with the third reference voltage Vth3, and compares the Lower signal with the Lower. If the signal is the third reference voltage Vth3 or higher, DL = "1" is output as the discrimination signal, and if the Lower signal is not the third reference voltage Vth3 or higher, DL = "0" is output as the discrimination signal.

The decoding circuit 12 is composed of a logic circuit, and includes a first AND (logical product) circuit 12a, a second AND (logical product) circuit 12b, a third AND (logical product) circuit 12c, and an OR (logic). W) The circuit 12d is provided.

The first AND circuit 12a performs a logical product operation by inputting a discrimination signal (DU) from the first 0/1 discriminator 11a and a discrimination signal (DL) from the third 0/1 discriminator 11c as inputs. ..

The second AND circuit 12b is logically input by inputting a discrimination signal (DU) from the first 0/1 discriminator 11a and a signal obtained by inverting the discrimination signal (DM) from the second 0/1 discriminator 11b. Perform a product operation.

The third AND circuit 12c is logically input by inputting a signal obtained by inverting the discrimination signal (DM) from the second 0/1 discriminator 11b and a discrimination signal (DL) from the third 0/1 discriminator 11c. Perform a product operation.

The OR circuit 12d performs a logical sum operation by inputting signals from the first AND circuit 12a, the second AND circuit 12b, and the third AND circuit 12c.

In the PAM decoder 2 described above, the first reference voltage Vth1 is set in the high voltage range H3, the second reference voltage Vth2 is set in the medium voltage range H2, and the third reference voltage Vth3 is set in the low voltage range H1. To do. When decoding the PAM4 signal, the first reference voltage Vth1 is used for punching the Upper signal, the second reference voltage Vth2 is used for punching the Middle signal, and the third reference voltage Vth3 is used for punching the Lower signal.

Further, in the decoding circuit 12, as shown in the truth table of FIG. 3B, the discrimination signal (DM) from the second 0/1 discriminator 11b is output as it is as the most significant bit string signal (MSB). The output of the OR circuit 12d is output as the least significant bit string signal (LSB). In FIG. 3B, when DU = 0, DM = 1, DL = 0, and when DU = 1, DM = 0, DL = 1, it is processed as Don't Care.

As a result, the PAM decoder 2 decodes the PAM4 signal into the most significant bit string signal (MSB) and the least significant bit string signal (LSB).

The decoding circuit 12 of the PAM decoder 2 is not limited to the circuit configuration of FIG. 2, and may have a configuration that satisfies the truth table of FIG. 3 (b).

The level measurement unit 3 measures the level of the most significant bit string signal (MSB) and the least significant bit string signal (LSB) decoded by the PAM decoder 2. Specifically, the level of the most significant bit string signal (MSB), the 0,1 level of the least significant bit string signal (LSB), and the 2nd and 3rd levels of the least significant bit string signal (LSB) are measured, respectively.

The error detection unit 4 uses the most significant bit string signal (MSB) and the least significant bit string signal (LSB) whose levels have been measured by the level measurement unit 3 as input data, and the level of each of the input data and the most significant bit string signal (MSB). ) And the level of the expected value data of each of the least significant bit string signals (LSB) to detect an error.

Further, based on the detected error, the error detection unit 4 sets the transition state (transition destination) for each symbol of the PAM4 signal according to the correspondence table of the error detection conditions with respect to the level of the expected value data shown in FIG. 4A. Level) is determined.

The expected value data of each of the most significant bit string signal (MSB) and the lowest bit string signal (LSB) is an object to be detected for error by a well-known circuit (oscillator, dividing circuit, inverting circuit, gray coder, precoder). It is generated according to the PAM4 signal (test signal) input to.

Here, the horizontal axis of FIG. 4A shows the level of the expected value data, and the vertical axis shows the level of the transition destination of the symbol.

In FIG. 4A, when the expected value data is level 0, the symbol of the PAM4 signal is level 0 if both the most significant bit string signal (MSB) and the least significant bit string signal (LSB) of the input data are errors. If only the most significant bit string signal (MSB) of the input data is an error, it is determined that the symbol of the PAM4 signal has transitioned from level 0 to level 2, and the least significant bit string signal of the input data is determined. If only (LSB) is an error, it is determined that the symbol of the PAM4 signal has transitioned from level 0 to level 1.

In FIG. 4A, when the expected value data is level 1, it is determined that the symbol of the PAM4 signal has transitioned from level 1 to level 3 if only the most significant bit string signal (MSB) of the input data is an error. If both the most significant bit string signal (MSB) and the least significant bit string signal (LSB) of the input data are errors, it is determined that the symbol of the PAM4 signal has transitioned from level 1 to level 2, and the least significant bit string signal of the input data is determined. If only (LSB) is an error, it is determined that the symbol of the PAM4 signal has transitioned from level 1 to level 0.

In FIG. 4A, when the expected value data is level 2, it is determined that the symbol of the PAM4 signal has transitioned from level 2 to level 3 if only the least significant bit string signal (LSB) of the input data is an error. If both the most significant bit string signal (MSB) and the least significant bit string signal (LSB) of the input data are errors, it is determined that the symbol of the PAM4 signal has transitioned from level 2 to level 1, and the most significant bit string signal of the input data is determined. If only (MSB) is an error, it is determined that the symbol of the PAM4 signal has transitioned from level 2 to level 0.

In FIG. 4A, when the expected value data is level 3, it is determined that the symbol of the PAM4 signal has transitioned from level 3 to level 2 if only the least significant bit string signal (LSB) of the input data is an error. If only the most significant bit string signal (MSB) of the input data is an error, it is determined that the symbol of the PAM4 signal has transitioned from level 3 to level 1, and the most significant bit string signal (MSB) of the input data and the lowest bit string signal (MSB) If both LSB) are errors, it is determined that the symbol of the PAM4 signal has transitioned from level 3 to level 0.

Then, the error detection unit 4 has three eye openings (3 eye openings based on the error count and error rate values according to the transition state of each symbol of the PAM4 signal determined according to the correspondence table of FIG. 4A). Upper Eye / Middle Eye / Lower Eye) The error count (EC) for each transition level and the error rate (ER) for each eye opening are detected.

When each error count (EC) of the transition destination for each level of each symbol in the list of FIG. 4 (a) is numbered as shown in FIG. 5, three eye openings (Upper) of the PAM4 signal are assigned. The error count (EC) for each transition level of Eye / Middle Eye / Lower Eye is as shown in FIG. If the transition of the symbol spans two or three levels, the number of eye openings that affect it will be two or three, so errors will be counted twice.

Further, the error rate (ER) for each eye opening (Upper Eye / Middle Eye / Lower Eye) is calculated by dividing the total value (Total) of the error counts (EC) of each eye opening by the number of measurement symbols. Will be done.

The display unit 5 is composed of a display such as a liquid crystal display, and a list of error counts and error rates according to the transition state of each symbol of the PAM4 signal determined by the error detection unit 4 is shown in FIG. 4, for example. Display in the display format of (b).

In the list of FIG. 4B, for example, for level 3 of the PAM4 signal symbol, the error count value of transitioning to level 2 is "6447", the error count value of transitioning to level 1 is "778", and the level. The value of the error count that has transitioned to 0 is "456", and the total value is "7681". Note that "ER" in FIG. 4B indicates the error rate for each level of the symbol of the PAM4 signal.

Further, the display unit 5 has an error count (EC) for each transition level of each of the three eye openings (Upper Eye / Middle Eye / Lower Eye) detected by the error detection unit 4, and an error rate for each eye opening. The list of (ER) is displayed in the display format shown in FIG. 6, for example.

In the list of FIG. 6, for example, for Upper Eye, the error count value of the 1st level transition is (3) + (6) = "435" + "6447" = "6882", and the error count value of the 2nd level transition is. (2) + (9) = "786" + "778" = "1564", the error count value of the three-level transition is (1) + (12) = "5768" + "456" = "6224", The total value of the error count is (1) + (2) + (3) + (6) + (9) + (12) = "5768" + "786" + "435" + "6447" + "778" + "456" = "14670".

The list of FIG. 4B and the list of FIG. 6 can selectively display either one or both on the display screen of the display unit 5.

Next, the error detection method by the error detection device 1 configured as described above will be described with reference to the flowchart of FIG.

First, the reference voltage for each voltage range is set (ST1). That is, the first reference voltage Vth1 in the low voltage range H1, the second reference voltage Vth2 in the medium voltage range H2, and the third reference voltage Vth3 in the high voltage range H3 are set respectively.

The PAM decoder 2 decodes the PAM4 signal from the error detection target into the most significant bit string signal (MSB) and the least significant bit string signal (LSB) (ST2).

Subsequently, the level measuring unit 3 measures the levels of the most significant bit string signal (MSB) and the least significant bit string signal (LSB) decoded by the PAM decoder 2 (ST3).

Next, the error detection unit 4 compares the levels of the most significant bit string signal (MSB) and the least significant bit string signal (LSB) measured by the level measurement unit 3 with the level of the expected value data, and detects an error. Then, based on the detected error, the transition state (transition destination level) for each level of each symbol of the PAM4 signal is determined according to the correspondence table of FIG. 4A (ST4).

Then, the error detection unit 4 has three eye openings (3 eye openings based on the error count and error rate values according to the transition state of each symbol of the PAM4 signal determined according to the correspondence table of FIG. 4A). Upper Eye / Middle Eye / Lower Eye) The error count (EC) for each transition level and the error rate (ER) for each eye opening are detected (ST5).

Then, the display unit 5 shows a list of error counts and error rates according to the transition state of each symbol of the PAM4 signal according to the display format shown in FIG. 4B, and three eye openings according to the display format shown in FIG. (Upper Eye / Middle Eye / Lower Eye) Selectively display one or both of the error count (EC) for each transition level and the error rate (ER) for each eye opening (ST6). ..

As described above, according to the present embodiment, as shown in FIG. 4B, the error count and error rate values according to the transition state of each symbol of the PAM4 signal are displayed in a list. As a result, it is possible to know to which level each symbol of the PAM4 signal has transitioned, and the transition state of each symbol including the transition destination of the level.

Further, as shown in FIG. 6, the error count and the error rate when each of the three eye openings (Upper Eye / Middle Eye / Lower Eye) are divided are displayed in a list. As a result, the error insertion state in each of the three eye openings can be seen at a glance, such as which eye opening the error is inserted unevenly and whether the error is evenly distributed in all the eye openings. become.

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

1 Error detection device 2 PAM decoder 3 Level measurement unit 4 Error detection unit 5 Display unit 11 0/1 discrimination circuit 11a 1st 0/1 discriminator 11b 2nd 0/1 discriminator 11c 3rd 0/1 discrimination Instrument 12 Decoding circuit 12a 1st AND circuit 12b 2nd AND circuit 12c 3rd AND circuit 12d OR circuit L0, L1, L2, L3 PAM4 Signal amplitude level H1 Low voltage range H2 Medium voltage range H3 High voltage range Vth1 1st reference voltage Vth2 2nd reference voltage Vth3 3rd reference voltage

Claims (4)

A PAM decoder (2) that decodes the PAM4 signal from the error detection target into the most significant bit string signal (MSB) and the least significant bit string signal (LSB), and
A level measuring unit (3) for measuring the levels of the highest-order bit string signal and the lowest-order bit string signal decoded by the PAM decoder, and
An error is detected by level comparison between the highest bit string signal and the lowest bit string signal measured by the level measuring unit and the expected value data of each of the highest bit string signal and the lowest bit string signal, and the expected value data. The error detection unit (4) that determines the transition state of each symbol of the PAM signal for each level based on the correspondence table of the error detection conditions with respect to the level of
A display unit (5) for displaying a list of error counts and error rates according to the transition state of each symbol of the PAM4 signal based on the determination result of the error detection unit is provided. Error detection device. The error detection unit (4) detects an error count for each transition level of each of the three eye openings of the PAM signal and an error rate for each eye opening from the transition state of each symbol of the PAM signal. And
The display unit (5) is a list of error counts and error rates according to the transition state of each symbol of the PAM4 signal, and each of the three eye openings of the PAM signal detected by the error detection unit. The error detection device according to claim 1, wherein a list of an error count for each transition level and an error rate for each eye opening is selectively displayed. The step of decoding the PAM4 signal from the error detection target into the most significant bit string signal (MSB) and the least significant bit string signal (LSB), and
The step of measuring the level of the decoded highest bit string signal and the lowest bit string signal, and
An error is detected by level comparison between the measured highest-order bit string signal and lowest-order bit string signal and the expected value data of each of the highest-order bit string signal and lowest-order bit string signal, and error detection with respect to the level of the expected value data. A step of determining the transition state of each symbol of the PAM signal for each level based on the condition correspondence table, and
An error detection method comprising a step of displaying a list of error counts and error rates according to a transition state of each symbol of the PAM4 signal based on the result of the determination. A step of detecting an error count for each transition level of each of the three eye openings of the PAM signal and an error rate for each eye opening from the transition state of each symbol of the PAM signal.
A list of error counts and error rates according to the transition state of each symbol of the PAM4 signal, an error count for each transition level of each of the three eye openings of the PAM signal, and an error rate for each eye opening. The error detection method according to claim 3, further comprising a step of selectively displaying a list of.

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