JP6594471B2 - Sampling oscilloscope and automatic scale method using the same - Google Patents

Description

  The present invention relates to a sampling oscilloscope that samples an optical signal as a signal under measurement and displays a waveform, and an automatic scale method using the sampling oscilloscope.

  Oscilloscopes have been widely used from research and development (R & D) to manufacturing processes. Autoscale processing, which is one of the functions of an oscilloscope, is used very frequently, particularly as a function for automatically setting an evaluation waveform to an appropriate scale display.

  By the way, auto scale processing is often implemented assuming all cases as a function, and processing that assumes multiple cases may be performed inside the measuring instrument. It is. Therefore, as a user, there is a demand for ideally reducing the processing time by performing measurement without executing the autoscale processing. In particular, in a process in which tact time is regarded as important, there is a great benefit that a lot of processing time can be shortened by not performing auto-scaling processing.

  However, sampling oscilloscopes, especially sampling oscilloscopes, use statistical processing on images in analysis, so that whether the scale is appropriate affects measurement accuracy, and in particular, in optical module manufacturing, the optical output power emitted from the DUT Since there is a large width even if the product name is the same, there is a risk in performing a production inspection on a fixed scale without executing auto-scaling at all.

  Therefore, autoscale processing that realizes appropriate scaling at high speed is an important index as one of the performance of equipment, especially in sampling oscilloscopes, and each company is striving to increase the speed.

  By the way, in general, in order to perform autoscale processing, the scale value of the vertical axis (Y axis) to be set is often obtained from the maximum value, minimum value, and average value of the signal under measurement. For example, Patent Document 1 below discloses a digital oscilloscope including a peak detection unit for determining the maximum value and the minimum value of a sample.

  In the auto-scaling process, in order to obtain the maximum value, the minimum value, and the average value of the signal under measurement, it is necessary to actually sample the signal under measurement. Therefore, the sampler circuit inside the device is driven, the waveform is sampled for a certain period, and the peak value and the average calculation are performed on the sampled data to obtain the maximum value, minimum value, and average value of the signal under measurement. However, only this can obtain scale information on the vertical axis (Y-axis). For this reason, after that, additional sampling is further performed, the horizontal axis (X-axis) scale information and phase offset including the waveform shape are obtained, and the auto-scaling process is completed.

JP 05-196647 A

  However, in the above-described autoscale processing, in order to obtain the first scale value of the vertical axis (Y-axis), it is necessary to drive the sampler circuit in an appropriate state. For example, it is necessary to change the gain of the IF circuit to an appropriate setting. For this reason, there is a problem in that it takes a long time to perform the process, such as measuring while changing the state of the hardware.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a sampling oscilloscope capable of reducing the processing time required for auto-scaling processing compared to the prior art and an auto-scaling method using the same. It is said.

To achieve the above object, a sampling oscilloscope according to claim 1 of the present invention is a sampling oscilloscope 1 that samples an optical signal as a signal under measurement at a predetermined sampling timing and displays a waveform on a display screen.
An extinction ratio setting means 2 for setting an extinction ratio of the optical signal;
A photoelectric converter 3 for converting the optical signal into an electrical signal;
Current detection means 7 for detecting a current value flowing through the photoelectric converter;
One value indicating the ratio of the extinction ratio based on the calculated average value and the extinction ratio set by the extinction ratio setting means is calculated from the current value detected by the current detection means. Parameter calculating means 8 for calculating the level and the Zero level;
And display control means for adjusting the vertical axis of the display screen based on the average value, One level, and Zero level of the optical signal calculated by the parameter calculation means.

The automatic scale method using the sampling oscilloscope according to claim 2 is an automatic scale method using the sampling oscilloscope 1 that samples an optical signal as a signal under measurement at a predetermined sampling timing and displays a waveform on a display screen.
Setting an extinction ratio of the optical signal;
Converting the optical signal into an electrical signal by a photoelectric converter;
Detecting a current value flowing through the photoelectric converter;
Calculating an average value of the optical signal from the current value, and calculating an One level and a Zero level indicating a ratio of the extinction ratio based on the calculated average value and the extinction ratio;
Adjusting the vertical axis of the display screen based on the average value, the One level, and the Zero level of the optical signal.

  According to the present invention, it is possible to reduce the processing time required for scaling adjustment of the vertical axis (Y axis) of the display screen in auto scale processing.

It is a block diagram which shows schematic structure of the sampling oscilloscope which concerns on this invention. FIG. 2 is a block diagram illustrating an example of an internal configuration of a trigger generation circuit in FIG. 1. (A) An example of an eye waveform after scaling adjustment on the vertical axis (Y axis) of the display screen, (b), (c) Crossing for adjusting the phase in the horizontal axis (X axis) direction of the display screen Explanatory drawing about the measurement of a coordinate, (d) It is a figure which shows an example of the eye waveform after the scaling adjustment of the vertical axis | shaft (Y axis) and a horizontal axis (X axis) of a display screen. 3 is a flowchart of a method for automatically scaling a sampling oscilloscope according to the present invention.

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

[Outline of the present invention]
When the signal under measurement is an optical signal, the average value of the input optical signal can be measured without using a sampler circuit by measuring the current value flowing through the photodiode of the photoelectric converter.

  Further, assuming that the signal under measurement is used in manufacturing inspection, the extinction ratio parameter assumed for the signal under measurement should exist as a design value. The extinction ratio is expressed as a ratio of One / Zero level. Therefore, if the average value and extinction ratio of the signal under measurement already known from the value of the current flowing through the photodiode of the photoelectric converter are given, generally the mark ratio of the signal under measurement is ½ in the manufacturing apparatus. Therefore, the scale of the vertical axis (Y axis) such as the One / Zero level can be measured and estimated.

  Therefore, in the present invention, the average extinction ratio of the signal under measurement, One / Zero level is set by setting the extinction ratio assumed for the optical signal as the signal under measurement and measuring the current value flowing through the photodiode of the photoelectric converter. And the scaling adjustment time on the vertical axis (Y-axis) in the optical signal auto-scaling process is reduced.

[Configuration of sampling oscilloscope]
As shown in FIG. 1, the sampling oscilloscope 1 of this embodiment displays the waveform of an optical signal as a signal under measurement, and the processing time required for scaling adjustment on the vertical axis (Y axis) of the display screen. In order to realize shortened autoscale processing, extinction ratio setting means 2, photoelectric converter (O / E) 3, trigger generation circuit 4, sampler 5, crossing coordinate measurement means 6, current detection means 7, parameter calculation means 8, a switching means 9, a display control means 10, and a display means 11 are schematically configured.

  The extinction ratio setting means 2 sets an extinction ratio expressed as a ratio between the One level (1 level) and the Zero level (0 level) of the optical signal as the signal under measurement.

  The photoelectric converter (O / E) 3 includes a photodiode as a photodetector, for example, and converts an optical signal as a signal under measurement input from the outside into an electric signal.

  The trigger generation circuit 4 generates a strobe signal used as a sampling timing at which the sampler 5 operates.

  More specifically, as shown in FIG. 2, the trigger generation circuit 4 includes, for example, a frequency converter 21, a direct digital synthesizer (hereinafter abbreviated as DDS) 22, a bandpass filter (hereinafter abbreviated as BPF). 23, an amplifier 24, and a variable frequency divider 25.

  The frequency conversion unit 21 is located in the first stage of the trigger generation circuit 4 and includes a variable frequency divider 21a and a frequency multiplication circuit 21b, and an input frequency range (1.25 GHz to 2.5 GHz) in which the DDS 22 located in the next stage can operate. The frequency of a trigger clock (for example, a rectangular wave or a sine wave) supplied from the outside is converted into an octave (a range of 2).

  The frequency converter 21 can handle the frequency division ratio of the variable frequency divider 21a and the frequency multiplication circuit 21b by a power of 2 if the operating frequency range of the DDS 22 is an octave (double) range. Become. The frequency converter 21 can be omitted when a trigger clock in the input frequency range in which the DDS 22 can operate is input from the outside. In this case, a trigger clock is directly input to the DDS 22 from the outside.

  The DDS 22 is connected to the next stage of the frequency conversion unit 21 and includes a reference clock generator, a phase accumulator, a ROM for storing waveform data, and a DAC (digital-analog conversion circuit).

  The DDS 22 digitally generates an arbitrary waveform or frequency (output frequency) from the trigger clock whose frequency is adjusted by the frequency converter 21 in the operating frequency range and frequency-converted by the frequency converter 21.

  The BPF 23 is connected to the next stage of the DDS 22 and limits the pass band of the trigger clock output from the DDS 22 in order to remove spurious.

  The amplifier 24 is composed of a low noise amplifier, and amplifies the amplitude of the trigger clock whose band is limited by the BPF 23.

The variable frequency divider 25 is connected to the next stage of the amplifier 24, and the frequency division ratio can be variably set (for example, 2 to 1/2 ³¹ ). In order to generate the sampling timing of the sampler 5, Provided on the stage. The variable frequency divider 25 adjusts the frequency of the trigger clock that passes through the BPF 23 and is amplified by the amplifier 24 to a frequency range in which the sampler 5 can operate.

  Here, the sampling timing period (strobe period) at which the sampler 5 can be driven is generally in the order of kHz, and it is not realistic to directly drive the sampler 5 at the output frequencies of the DDS 22 and the BPF 23. Therefore, the last-stage variable frequency divider 25 divides the frequency of the trigger clock that has passed through the BPF 23 to a frequency that the sampler 5 can drive, and outputs a strobe signal that is the sampling timing of the sampler 5.

  The sampler 5 performs a switching operation (closed state: for example, 10 to 100 psec) with a strobe signal generated by the trigger generation circuit 4 at a sampling timing of, for example, several hundred kHz, and is converted into an electric signal by the photoelectric converter 3. Sampling the measurement signal.

  The crossing coordinate measuring means 6 measures crossing coordinates for adjusting the phase in the horizontal axis (X-axis) direction. The measured crossing coordinates are output to the display control means 10 via the switching means 9.

  The current detection means 7 is provided at the subsequent stage of the photoelectric converter 3 and detects the value of the current flowing through the photodiode provided in the photoelectric converter 3.

  The parameter calculation means 8 calculates the average value, the One level, and the Zero level of the signal under measurement as parameters necessary for performing scaling adjustment on the vertical axis (Y axis). The calculated One level, Zero level, and average value of the signal under measurement are output to the display control means 10 via the switching means 9.

  More specifically, the parameter calculation means 8 calculates the average value of the signal under measurement from the current value (A / D converted value) detected by the current detection means 7. The parameter calculation means 8 calculates the One level and the Zero level based on the calculated average value and the extinction ratio set by the extinction ratio setting means 2. Specifically, with the mark ratio = 1/2, the extinction ratio = One / Zero (1) and the average value = (One + Zero) × 1/2 (2) From the simultaneous equations of the formula (2), the One level, Zero Calculate the level.

  The switching unit 9 is controlled to be connected so that the parameter calculation unit 8 and the display control unit 10 are connected when the scaling adjustment of the vertical axis (Y axis) of the display screen of the display unit 11 is performed. The switching unit 9 connects the crossing coordinate measuring unit 6 and the display control unit 10 when performing the scaling adjustment on the horizontal axis (X axis) and the fine adjustment on the vertical axis (Y axis) of the display screen of the display unit 11. The switching is controlled so that

  The display control means 10 controls the display means 11 so as to display the waveform of the signal under measurement based on the sample data from the sampler 5.

  Further, the display control means 10 performs auto-scaling processing on the vertical axis (Y axis) of the display screen of the display means 11 based on the One level, Zero level, and average value of the signal under measurement calculated by the parameter calculation means 8. Adjust the scaling.

  Further, the display control means 10 performs scaling adjustment on the horizontal axis (X axis) of the display screen of the display means 11 based on the crossing coordinates measured by the crossing coordinate measurement means 6 as auto-scaling processing. Further, the One level and the Zero level are statistically calculated from the image displayed on the display screen of the display unit 11 using a histogram, and the vertical axis (Y axis) of the display screen is calculated using the calculated One level and Zero level. Make fine adjustments.

  The display means 11 is composed of, for example, a liquid crystal display. The display unit 11 displays the waveform of the signal under measurement based on the sample data obtained by the sampler 5 on the display screen under the control of the display control unit 10.

  Further, the display unit 11 performs the scaling adjustment on the horizontal axis (X) after the vertical axis (Y axis) of the display screen is scaled and adjusted under the control of the display control unit 10 as autoscale processing. Further, the vertical axis (Y axis) of the display screen is finely adjusted as necessary.

  Next, autoscale processing of the sampling oscilloscope 1 configured as described above will be described with reference to FIG.

  In executing the auto scale processing, the extinction ratio is preset by the extinction ratio setting means 2 (ST1). Further, the switching means 9 is controlled to be connected so that the parameter calculation means 8 and the display control means 10 are connected.

  When an optical signal as a signal under measurement is input to the photoelectric converter 3, the optical signal is converted into an electric signal by the photoelectric converter 3, and then the strobe signal generated by the trigger generation circuit 4 is sampled. Sampled by the sampler 5 as timing (ST2).

  At that time, the current detection means 7 detects the current value flowing through the photodiode included in the photoelectric converter 3 (ST3). The parameter calculation means 8 calculates the average value of the signal under measurement from the current value detected by the current detection means 7, and based on the calculated average value and the extinction ratio set by the extinction ratio setting means 2. Level and Zero level are calculated (ST4).

  Then, the display control means 10 performs scaling adjustment of the vertical axis (Y axis) of the display screen of the display means 11 based on the One level, Zero level, and average value of the signal under measurement calculated by the parameter calculation means 8 ( ST5).

  In the scaling adjustment of the vertical axis (Y axis) of the display screen of the display means 11, the calculated average value of the signal under measurement becomes the offset of the vertical axis (Y axis) scale, and the center of the vertical axis of the display screen of the display means 11. Set to a value. The difference between the calculated One level and Zero level is the amplitude of the observation signal.

  Specifically, for example, as shown in FIG. 3A, when the full scale of the display screen of the display unit 11 is set to the amplitude of all 10 squares, and the waveform is drawn using 5 squares of 10 squares, the amplitude of the observation signal Is full scale / 2.

  Therefore, since full scale = 10 squares × amplitude value (division) per square, the amplitude of the observation signal is (10 × division) / 2. Thereby, the amplitude value (Division) per square is set to the amplitude of the observation signal / 5. It should be noted that the phase in the horizontal axis (X axis) direction of the display screen of the display means 11 is shifted at the stage where the scaling adjustment of the vertical axis (Y axis) is completed.

  Therefore, in order to perform scaling adjustment on the horizontal axis (X axis) of the display screen of the display unit 11, the switching unit 9 is controlled so as to connect the crossing coordinate measuring unit 6 and the display control unit 10.

  Then, the crossing coordinate measuring means 6 measures the crossing coordinates for adjusting the phase in the horizontal axis (X-axis) direction. Specifically, first, it is confirmed whether or not sample data exists near the center of the left end of the display screen of the display means 11. Then, as shown in FIG. 3B, when there is no sample data at the left end of the display screen, the average of the histogram of the range from the left end of the display screen to the center of the display screen (the range indicated by the dotted line in FIG. 3B) Measure crossing coordinates by value. On the other hand, as shown in FIG. 3C, when sample data exists at the left end of the display screen, the average of the histograms at the center of the display screen (the range of 25 to 75% indicated by the dotted line in FIG. 3C). The crossing coordinate is measured by the value (ST6).

  Then, the display control means 10 performs scaling adjustment on the horizontal axis (X axis) of the display screen of the display means 11 based on the crossing coordinates measured by the crossing coordinate measuring means 6 (ST7).

  In the scaling adjustment of the horizontal axis (X axis) of the display screen of the display means 11, the crossing coordinates of the eye waveform are set to 25% and 75% in the specific area of the display screen (in the case of 2 UI, the horizontal axis (X axis)). Therefore, the offset of the horizontal axis (X axis) is set so that the measured crossing coordinates are at the 25% or 75% coordinates (for example, the state of FIG. 3D). When displaying an eye waveform, the X coordinate of the display screen may be fixed to 2 UI.

  Further, regarding fine adjustment of the vertical axis (Y axis) of the display screen of the display unit 11, in the case of an eye waveform, since crossing +0.5 UI is considered as the eye opening center, for example, at the eye opening center, a histogram is obtained from the image. Is used to statistically calculate the One level and the Zero level, and the difference between the calculated One level and the Zero level is set as the amplitude of the observation signal. As described above, when the full scale of the display screen of the display unit 11 is set to the amplitude of all 10 squares, and the waveform is drawn using 5 squares in 10 squares, the amplitude value (Division) per square is set. Set the observation signal amplitude to 5 and finely adjust the vertical axis (Y-axis).

  Thus, according to the present embodiment, it is possible to reduce the processing time required for the scaling adjustment of the vertical axis (Y axis) of the display screen in the autoscale processing most frequently used in the sampling oscilloscope. Specifically, for example, of the entire auto-scaling process, about 400 seconds can be shortened by scaling adjustment on the vertical axis (Y-axis), and the processing speed can be increased by about 20% compared to the prior art. .

  In addition, since the optical output power that is likely to vary depending on the measurement object (DUT) is measured with the sampling oscilloscope 1 and is subjected to scaling adjustment, it is possible to eliminate the concern when the user carries out with a fixed scale.

  By the way, in the above-described embodiment, an example of the auto-scaling process in the case of sampling and displaying a waveform of a signal under measurement of one channel has been described as an example. Alternatively, it can be applied to auto-scaling processing for switching display. In this case, as the number of channels increases, the processing time required for scaling adjustment on the vertical axis (Y-axis) can be shortened, and the entire autoscale process can be accelerated.

  The best mode of the sampling oscilloscope and the automatic scale method using the sampling oscilloscope according to the present invention has been described above, but the present invention is not limited to the description and drawings according to this mode. That is, it is a matter of course 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.

DESCRIPTION OF SYMBOLS 1 Sampling oscilloscope 2 Extinction ratio setting means 3 Photoelectric converter (O / E)
DESCRIPTION OF SYMBOLS 4 Trigger generation circuit 5 Sampler 6 Crossing coordinate measurement means 7 Current detection means 8 Parameter calculation means 9 Switching means 10 Display control means 11 Display means 21 Frequency conversion part 21a Variable frequency divider 21b Frequency multiplication circuit 22 DDS (direct digital synthesizer) )
23 BPF (band pass filter)
24 amplifier 25 variable frequency divider

Claims (2)

In a sampling oscilloscope (1) for sampling an optical signal as a signal under measurement at a predetermined sampling timing and displaying the waveform on a display screen,
An extinction ratio setting means (2) for setting an extinction ratio of the optical signal;
A photoelectric converter (3) for converting the optical signal into an electrical signal;
Current detection means (7) for detecting a current value flowing through the photoelectric converter;
One value indicating the ratio of the extinction ratio based on the calculated average value and the extinction ratio set by the extinction ratio setting means is calculated from the current value detected by the current detection means. Parameter calculating means (8) for calculating the level and the Zero level;
Sampling comprising: display control means (10) for adjusting the scaling of the vertical axis of the display screen based on the average value, One level, and Zero level of the optical signal calculated by the parameter calculation means. oscilloscope. In an automatic scale method using a sampling oscilloscope (1) for sampling an optical signal as a signal under measurement at a predetermined sampling timing and displaying the waveform on a display screen,
Setting an extinction ratio of the optical signal;
Converting the optical signal into an electrical signal by a photoelectric converter;
Detecting a current value flowing through the photoelectric converter;
Calculating an average value of the optical signal from the current value, and calculating an One level and a Zero level indicating a ratio of the extinction ratio based on the calculated average value and the extinction ratio;
Adjusting the vertical axis of the display screen based on the average value, the One level, and the Zero level of the optical signal, and an automatic scaling method using a sampling oscilloscope.