JP2007093296A - Sampling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a sampling device for acquiring correction data without being affected by a clock signal that is synchronized with the signal under measurement. <P>SOLUTION: This sampling device is one improved of a sampling device for repeated sampling of the signal under measurement. This device is equipped with a sampling circuit for a signal under measurement used to sample a signal under measurement; a reference signal generation circuit for outputting a reference signal with known frequency; a sampling circuit for sampling the reference signal; a frequency conversion circuit for generating a strobe signal for sampling from a clock signal; a correction data storage means for storing therein the correction data; a time-base calculation means for finding time-base information on the sampling circuit for the signal under measurement, based on data from the sampling circuit and on the correction data; a correction data calculation means for finding correction data from the phase of the calculation means; and a modulation signal generation circuit for modulating the reference signal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sampling apparatus that repeatedly samples a signal under measurement, and more particularly to a sampling apparatus that can acquire correction data without being affected by a clock signal synchronized with the signal under measurement.

  The sampling device repeatedly samples (samples) a signal under measurement output from the device under measurement in a sampling oscilloscope, for example. In addition to a sampling oscilloscope, it is also used in a jitter measuring device such as a time interval analyzer.

  The sampling oscilloscope repeatedly samples the signal under measurement while shifting the phase, and reproduces the waveform based on the phase. A conventional sampling oscilloscope samples the clock signal synchronized with the signal under measurement as phase information, calculates the phase information of the clock signal from the amplitude information of the sampled clock signal, and obtains the signal under measurement from the obtained phase information. The sampled time is obtained, and the waveform of the signal under measurement is generated.

  FIG. 9 is a diagram showing a configuration of a conventional sampling oscilloscope (see, for example, Patent Documents 1 and 2). In FIG. 9, a device under test 10 outputs a signal under measurement and a clock signal synchronized with the signal under measurement (hereinafter abbreviated as a synchronous clock signal).

  The sampling oscilloscope 20 includes sampling circuits 21 to 23, a low-pass filter circuit (hereinafter abbreviated as LPF (Low Pass Filter)) 24, a phase adjustment circuit 25, a time base calculation means 26, and a strobe signal generation circuit 27. A signal under measurement and a synchronous clock signal are input from the measuring apparatus 10.

  The sampling circuit 21 receives a signal under measurement from the device under measurement 10. The LPF 24 receives a synchronous clock signal from the device under test 10. The phase adjustment circuit 25 receives the signal filtered by the LPF 24. Sampling circuits 22 and 23 receive the output signal of phase adjustment circuit 25. The time base calculation means 26 receives the signals sampled by the sampling circuits 22 and 23. The strobe signal generation circuit 27 outputs a strobe signal to the sampling circuits 21 to 23.

The operation of such an apparatus will be described.
Each of the signal under measurement and the synchronous clock signal is input from the device under measurement 10 to the sampling circuit 21 and the LPF 24 of the sampling oscilloscope 10. Then, the LPF 24 shapes the synchronous clock signal into a sine wave and outputs it to the phase adjustment circuit 25. Further, the phase adjustment circuit 25 delays the shaped sine wave to generate a cosine wave orthogonal to the sine wave, outputs the sine wave to the sampling circuit 22, and outputs the cosine wave to the sampling circuit 23.

  Each of the sampling circuits 21 to 23 simultaneously samples the input signals (signal under measurement, sine wave, cosine wave) by the same strobe signal from the strobe signal generation circuit 27.

  The sampling results of the sampling circuits 22 and 23 are input to the time base calculation means 26. Then, the time base calculation means 26 calculates the phase obtained by sampling the synchronous clock signal from the sampling value. Further, since the sampling times of the sampling circuits 21 to 23 are the same, the sampling time of the signal under measurement is obtained from the calculated phase information.

  Further, since the period of the strobe signal output from the strobe signal generation circuit 27 is known, the time base calculation means 26 fits the sampling value to the sine wave by, for example, the least square method, and sets the frequency of the synchronous clock signal. presume. Then, the phase of the synchronous clock signal at the time of sampling is obtained by comparing the estimated sine wave of the estimated frequency with the amplitude of the sampling value and referencing the phase in reverse. Further, the sampling time is obtained based on the obtained phase information.

  A waveform generation unit (not shown) generates a waveform of the signal under measurement from the amplitude of the signal under measurement by the sampling circuit 21 and the sampling time by the time base calculation unit 26 and displays the waveform on a display unit (not shown).

Next, jitter will be described. The jitter includes jitter of the synchronous clock signal itself and jitter by the strobe signal generation circuit 27.
The jitter of the synchronous clock signal is detected as a phase change of the sine wave and the cosine wave by sampling in the sampling circuits 22 and 23. Therefore, time information on the horizontal axis including the jitter of the synchronous clock signal can be obtained. Similarly, the jitter of the synchronous clock signal causes fluctuations in the sampling timing in the sampling circuit 21 and affects the change in the amplitude information on the vertical axis. In other words, since the horizontal axis and the vertical axis include jitter, the jitter of the synchronous clock signal is canceled out, and the measurement result is obtained by correcting the jitter of the synchronous clock signal.

  On the other hand, the jitter of the strobe signal generation circuit 27 affects the sampling in the sampling circuits 21 to 23, but the sampling of the sampling circuits 21 to 23 is performed at the same time by the same strobe signal. Therefore, the jitter of the strobe signal is canceled out, resulting in a measurement result in which the jitter of the strobe signal is corrected.

JP 2003-66070 A JP 2003-130892 A

  In this way, jitter on the time axis is canceled by sampling not only the signal under measurement but also the synchronous clock signal. However, since each circuit (phase adjustment circuit 25 and sampling circuits 22 and 23) used for canceling jitter is not an ideal circuit, various errors (for example, distortion of sine wave and cosine wave by the phase adjustment circuit 25). , Amplitude error, phase error, non-linearity due to the sampling circuits 22 and 23, offset error, etc.), which leads to an error (increase in jitter) in obtaining an accurate sampling time.

  Conventionally, for example, before the sampling oscilloscope 20 is shipped from a manufacturer's factory, an ideal synchronous clock signal (having a high-quality waveform and a predetermined frequency) can be used instead of the device under test 10. Signal) is connected, and correction data for correcting the error of each circuit is acquired.

  Specifically, a device for outputting a signal under measurement for correction and a synchronous clock that can input ideal sine waves and cosine waves to the sampling circuits 22 and 23 is prepared, and the strobe signal generation circuit 27 performs phase adjustment. The ratio of the strobe signal frequency to the output frequency from the circuit 25 is adjusted so as not to be divisible by an integer or a decimal first.

  Then, the difference between the outputs of the sampling circuits 22 and 23 and the input ideal waveform is detected to obtain correction data. The reason why the frequency of the synchronous clock signal is set to a specific known value is to avoid sampling at the same phase position. That is, the correction data is acquired so that the sampling time can be predicted in advance and has a large number of different values.

  Even if correction is performed with such correction data, a new error occurs in each circuit due to aging, temperature change, etc., while the user uses it, and it becomes necessary to acquire correction data again.

  However, in order to correct the waveform distortion and the like of the synchronous clock signal, the LPF 24 removes spurious components and extracts a sinusoidal waveform, but the band of the synchronous clock signal is several [GHz] to several tens [[ Since it has a very wide bandwidth such as [GHz], a plurality of LPFs 24 having different cutoff frequencies must be provided and switched. For this reason, if the frequency of the synchronous clock signal changes, the shape of the waveform after filtering naturally changes, so there is a problem that the frequency of the synchronous clock signal must be recognized and correction data must be acquired for each frequency. .

  Further, when the waveform quality of the synchronous clock signal changes, the shape of the waveform input to the sampling circuits 22 and 23 via the LPF 24 also changes, and there is a problem that correction data must be acquired again.

  Accordingly, an object of the present invention is to realize a sampling apparatus that can acquire correction data without being affected by a clock signal synchronized with a signal under measurement.

The invention described in claim 1
In a sampling device that repeatedly samples a signal under measurement,
A sampling circuit for a signal under measurement for sampling the signal under measurement;
A reference signal generating circuit for outputting a reference signal having a known frequency;
A sampling circuit that samples the reference signal of the reference signal generation circuit;
A frequency conversion circuit for generating a strobe signal for starting sampling by the sampling circuit and the signal under measurement sampling circuit from a clock signal synchronized with the signal under measurement;
Correction data storage means for storing correction data for correcting measurement errors;
A time base calculating means for obtaining a phase from a sampling value of the sampling circuit, correcting the obtained phase with the correction data of the correction data storage means, and obtaining time axis information of the sampling circuit for the signal under measurement;
Correction data calculation means for obtaining the correction data from the phase of the time base calculation means and storing the correction data in the correction data storage means;
And a modulation signal generation circuit for frequency-modulating or phase-modulating the reference signal of the reference signal generation circuit.
The invention according to claim 2
In a sampling device that repeatedly samples a signal under measurement,
A sampling circuit for a signal under measurement for sampling the signal under measurement;
A reference signal generating circuit for outputting a reference signal having a known frequency;
A sampling circuit that samples the reference signal of the reference signal generation circuit;
A frequency conversion circuit for generating a strobe signal for starting sampling by the sampling circuit and the signal under measurement sampling circuit from a clock signal synchronized with the signal under measurement;
Correction data storage means for storing correction data for correcting measurement errors;
A time base calculating means for obtaining a phase from a sampling value of the sampling circuit, correcting the obtained phase with the correction data of the correction data storage means, and obtaining time axis information of the sampling circuit for the signal under measurement;
Correction data calculation means for obtaining the correction data from the phase of the time base calculation means and storing the correction data in the correction data storage means;
A modulation signal generation circuit for frequency-modulating or phase-modulating the strobe signal of the frequency conversion circuit is provided.
The invention according to claim 3 is the invention according to claim 1 or 2,
The modulation signal generating circuit is characterized by performing frequency modulation or phase modulation when the correction data calculation means calculates correction data.
The invention according to claim 4 is the invention according to any one of claims 1 to 3,
The modulation signal generating circuit performs frequency modulation or phase modulation so that a ratio between the frequency of the reference signal and the frequency of the strobe signal does not become a value that is divisible by an integer or a first decimal place.
The invention according to claim 5
In a sampling device that repeatedly samples a signal under measurement,
A sampling circuit for a signal under measurement for sampling the signal under measurement;
A reference signal generation circuit that outputs a reference signal with a known frequency and has a variable frequency;
A sampling circuit that samples the reference signal of the reference signal generation circuit;
A frequency conversion circuit for generating a strobe signal for starting sampling by the sampling circuit and the signal under measurement sampling circuit from a clock signal synchronized with the signal under measurement;
Correction data storage means for storing correction data for correcting measurement errors;
A time base calculating means for obtaining a phase from a sampling value of the sampling circuit, correcting the obtained phase with the correction data of the correction data storage means, and obtaining time axis information of the sampling circuit for the signal under measurement;
A correction data calculation means for obtaining the correction data from the phase of the time base calculation means and storing the correction data in the correction data storage means is provided.
The invention according to claim 6 is the invention according to claim 5,
When the correction data calculation means calculates correction data, the reference signal generation circuit changes the frequency so that the ratio between the frequency of the reference signal and the frequency of the strobe signal does not become a value that is divisible by an integer or a first decimal place. It is characterized by doing.

The present invention has the following effects.
According to the first, third, and fourth aspects, the reference signal generating circuit outputs a reference signal having a known frequency. Then, the sampling circuit samples the reference signal with the strobe signal obtained by converting the synchronous clock signal, and the time base calculation means obtains the sampling time of the signal under measurement from the sampling value and the correction data in the correction data storage means. On the other hand, in the case of acquisition of correction data, the modulation signal generation circuit performs phase modulation or frequency modulation on the reference signal. Thus, the data obtained by sampling the reference signal with the strobe signal does not sample only the same phase point or limited phase point of the reference signal, and samples a wide range of phase points. Therefore, even if the frequency of the clock signal synchronized with the signal under measurement is unknown or the waveform quality is poor, correction data for a wide range of phase points can be acquired without being affected by the clock signal.
According to the second to fourth aspects, the reference signal generating circuit outputs a reference signal having a known frequency. Then, the sampling circuit samples the reference signal with the strobe signal obtained by converting the synchronous clock signal, and the time base calculation means obtains the sampling time of the signal under measurement from the sampling value and the correction data in the correction data storage means. On the other hand, in the case of obtaining correction data, the modulation signal generation circuit performs phase modulation or frequency modulation on the strobe signal. Thus, the data obtained by sampling the reference signal with the strobe signal does not sample only the same phase point or limited phase point of the reference signal, and samples a wide range of phase points. Therefore, even if the frequency of the clock signal synchronized with the signal under measurement is unknown or the waveform quality is poor, correction data for a wide range of phase points can be acquired without being affected by the clock signal.
According to claims 5 and 6, the reference signal generation circuit outputs a reference signal having a known frequency. Then, the sampling circuit samples the reference signal with the strobe signal obtained by converting the synchronous clock signal, and the time base calculation means obtains the sampling time of the signal under measurement from the sampling value and the correction data in the correction data storage means. On the other hand, when acquiring correction data, the reference signal generation circuit changes the frequency of the reference signal to a desired frequency. Thus, the data obtained by sampling the reference signal with the strobe signal does not sample only the same phase point or limited phase point of the reference signal, and samples a wide range of phase points. Therefore, even if the frequency of the clock signal synchronized with the signal under measurement is unknown or the waveform quality is poor, correction data for a wide range of phase points can be acquired without being affected by the clock signal.

Embodiments of the present invention will be described below with reference to the drawings.
[First embodiment]
FIG. 1 is a block diagram showing a first embodiment of the present invention. Here, the same components as those in FIG. 9 are denoted by the same reference numerals, and description thereof is omitted. In FIG. 1, a sampling oscilloscope Osi is provided instead of the oscilloscope 20. The sampling oscilloscope Osi includes sampling circuits 31 to 33, 42 and 43, a reference signal generation circuit 34, frequency conversion circuits 35 and 36, a time base calculation unit 37, a waveform generation unit 38, a display unit 39, a storage unit 40, and a phase adjustment circuit. 41, a modulation signal generation circuit 44, a correction data calculation means 45, and a correction data storage means 46.

  The sampling oscilloscope Osi receives the signal under measurement S1 and the synchronous clock signal S2 from the device under measurement 10 and performs waveform analysis, waveform display, etc. of the signal under measurement. Of course, the synchronous clock signal S2 is a clock signal synchronized with the signal under measurement S1.

  The sampling circuits 31 to 33, 42 and 43, the reference signal generation circuit 34, the frequency conversion circuits 35 and 36, the time base calculation means 37, the waveform generation means 38, the phase adjustment circuit 41, the modulation signal generation circuit 44, the correction data calculation. Means 45 and correction data storage means 46 constitute a sampling device.

  The signal under measurement sampling circuit 31 samples the signal under measurement S1 from the device under measurement 10, and outputs the sampling result (amplitude value of the signal under measurement) to the waveform generation means 38 as the vertical axis information signal S3.

  The first frequency conversion circuit 35 converts the frequency of the synchronous clock signal S2 from the device under test 10 and outputs a first strobe signal S4 having a phase synchronized with the synchronous clock signal S2 and having a different frequency.

  The second frequency conversion circuit 36 converts the frequency of the synchronous clock signal S2 from the device under test 10 and outputs a second strobe signal S5 having a phase that is synchronized with the phase of the synchronous clock signal S2 and having a different frequency. Note that the strobe signals S4 and S5 have different frequencies.

  As an example, the frequency conversion circuit 35 is a frequency synthesizer using a phase locked loop, and generates signals having different frequencies while referring to the synchronous clock signal S2. Another example is a frequency mixer (so-called mixer) with a local oscillator, which generates a signal having a frequency that is down-converted by a local oscillator synchronized with the synchronous clock signal S2.

  On the other hand, the frequency conversion circuit 36 is a frequency divider such as a prescaler or a frequency divider, for example.

  The reference signal generation circuit 34 is an oscillator having a narrow band of about 5 GHz, for example, and outputs a highly stable reference signal S6 with a known frequency and less waveform distortion. The output waveform is not limited to a sine wave, and may be any waveform that uniquely determines the phase corresponding to the continuous amplitude, such as a sawtooth wave.

  The phase adjustment circuit 41 generates and outputs a reference signal S6 from the reference signal generation circuit 34 as a second reference signal S10 having a phase different from that of the reference signal S6 (for example, the phase is orthogonal). For example, if the reference signal S6 is a sine wave, the reference signal S10 is a cosine wave.

  The modulation signal generation circuit 44 modulates the reference signal S6 output from the reference signal generation circuit 34. It should be noted that the modulation is not performed when the signal under measurement S1 is measured, but is performed when correction data for correction is obtained. The modulation signal generation circuit 44 applies phase modulation or frequency modulation with a random frequency signal having a wideband frequency component or a signal having an arbitrary frequency. Of course, the amplitude of the reference signal S6 is not modulated.

  The first and second sampling circuits 32 and 33 sample the reference signal S6 from the reference signal generation circuit 34, and output reference signals S7 and S8 as sampling results to the time base calculation means 37.

  The third and fourth sampling circuits 42 and 43 sample the reference signal S10 from the phase adjustment circuit 41, and output reference signals S11 and S12 as sampling results to the time base calculation unit 37.

  The signal under measurement sampling circuit 31 and the first and third sampling circuits 32 and 42 are given sampling timing by the strobe signal S4 from the first frequency conversion circuit 35 and start sampling.

  The second and fourth sampling circuits 33 and 43 are given sampling timing by the strobe signal S5 from the second frequency conversion circuit 36, and start sampling.

  Further, the strobe signal S4 from the frequency conversion circuit 35 is slightly shifted (for example, 9999/10000) from the frequency obtained by down-converting the synchronous clock signal S2. The sampling circuit 31 is detected by the strobe signal S4. Sequentially samples the signal under measurement. That is, sampling is performed by a sequential sampling method.

  The sampling circuits 31 to 33, 42 and 43 are, for example, a sampler, an analog / digital converter having a necessary and sufficient accuracy with respect to the measured signal S1 and the reference signals S6 and S10, a frequency mixer (mixer), or the like. is there.

  The time base calculation means 37 receives the reference signals S7, S8, S11, S12 from the sampling circuits 32, 33, 42, 43, and samples the reference signals S6, S7 or the reference signals S6, S10 from the reference signals S11, S12. The obtained phase is obtained, the sampled timing (time interval) is calculated from the obtained phase, and the time axis information of the obtained timing is output to the waveform generating means 38 as the horizontal axis (time axis) information signal S9. Further, if the correction data exists in the correction data storage means 46, the time base calculation means 37 reads the correction data, corrects the obtained phase, and then calculates the timing.

  The correction data calculation unit 45 obtains correction data from the phase obtained by the time base calculation unit 37 and stores the obtained correction data in the correction data storage unit 46. The correction data here is for correcting errors generated by the reference signal generation circuit 34, the sampling circuits 32, 33, 42, 43, the phase adjustment circuit 41, and the frequency conversion circuits 35, 36.

  The waveform generation means 38 generates a waveform of the signal under measurement S1 from the vertical axis information signal S3 and the horizontal axis information signal S9, displays the waveform on the display means 39, and generates the waveform generated in the storage means 40 in an appropriate format. Remember and save.

  The time base calculation unit 37 and the waveform generation unit 38 are, for example, a computer system including a CPU (Central Processing Unit), a signal processing unit including a DSP (Signal Processing Processor), and the like, and distinguishing between hardware and software It doesn't matter.

  The display means 39 is, for example, a CRT (cathode ray tube), LCD (liquid crystal display), organic EL (electroluminescence) display, plasma display, electron tube, or the like.

  Furthermore, the recording means 40 is, for example, a pen recorder, HD (hard disk), CD (compact disk), DVD (multifunctional disk), FD (floppy (registered trademark) disk), USB memory, or the like.

  First, the principle of reproducing the sampling of the apparatus shown in FIG. 1 and the waveform of the signal under measurement S1 will be described with reference to FIG. FIG. 2 is a diagram showing the sampling timing of the apparatus shown in FIG. 1, and the waveform reproduction of the signal under measurement S1 and the reference signal S6. In FIG. 2, the horizontal axis represents time, and the vertical axis represents the amplitude of the signal under measurement S1 and the reference signal S6.

  Times ts0 to ts6 (sampling interval Ts) indicate the timing for sampling by the strobe signal S4, and times tr0 to tr3 (sampling interval Tr) indicate the timing for sampling by the strobe signal S5. Further, Tr ≠ Ts, and ΔTs = Ts−Tr. Of course, sampling is repeated after ts6 and tr3, but the illustration is omitted.

  One cycle of the reference signal S6 is Tf, a cycle closest to the interval Tr within a range not exceeding the interval Tr of the strobe signal S5 is Tf × m (m is an integer), and ΔTr = Tr−Tf × m.

  Also, the times ts0 and tr0 are the same time. In order to simplify the explanation, the time ts0 is defined as a zero cross point (a point where the amplitude changes from minus to plus) of the signal under measurement S1 and the reference signal S6.

  Here, if the time ts0 is a reference time, the time interval between the timings ts1 to ts6 of the strobe signal S4 and the strobe signals tr1 to tr3 obtained by dividing the synchronous clock signal S2 is ΔTs, 2 × ΔTs, 3 × ΔTs. ...

  Since the sampling circuit 31 performs sampling with a deviation of ΔTs with respect to the phase of the signal under measurement S1, that is, decomposes into ΔTs, the sampling point of the signal under measurement S1 (the black dot on the signal under measurement S1 in FIG. 2) ) Are reproduced, the waveform of the original signal under measurement S1 is reproduced. Similarly, since the cycle of the reference signal S6 and the strobe signal S5 is shifted, the waveform of the original reference signal S6 is obtained by connecting the sampling points of the reference signal S6 (black points on the reference signal S6 in FIG. 2). It is reproduced.

  Note that the deviation of ΔTs with respect to the phase of the signal under measurement S1 corresponds to the real time when the signal under measurement S1 is reproduced. That is, if ΔTs is increased, the time interval between the sampling points of the reproduced waveform becomes coarse, and if ΔTs is reduced, the time interval becomes finer. Therefore, ΔTs is the time resolution of the sampling circuit 31. ΔTs can be set to a desired time difference ΔTs by the frequency conversion circuit 35. Similarly, as shown in FIG. 2, the time resolution of the sampling circuit 32 is ΔTs + ΔTr, and the time resolution of the sampling circuit 33 is ΔTr.

  Also, the sampling circuits 42 and 43 sample the reference signal S10 and reproduce the waveform of the signal under test S1 in FIG. 2, because the sampling circuits 42 and 43 correspond to the sampling circuits 32 and 33 in FIG. Since the phase of the signal S10 is the same except that it is shifted by 90 ° with respect to the sine wave reference signal S6, the description is omitted.

Next, the operation of such an apparatus will be described. First, the operation when measuring the signal under measurement S1 will be described, and then the operation when acquiring correction data will be described.
A signal under test S1 is input from the device under test 10 to the sampling circuit 31, and a synchronous clock signal S2 is input to the frequency conversion circuits 35 and 36. Further, the reference signal generation circuit 34 outputs the reference signal S6 to the sampling circuits 32 and 33.

  The phase adjustment circuit 41 adjusts the phase of the reference signal S6 from the reference signal generation circuit 34 to a reference signal S10 orthogonal to the reference signal S6. For example, if the reference signal S6 is a sine wave, the phase is adjusted to 90. The cosine wave delayed by 50 degrees is output to the sampling circuits 42 and 43.

  Then, the frequency conversion circuit 35 outputs a strobe signal S4 that is lower than the frequency of the synchronous clock signal S2 (for example, about 1/1000) and slightly different in frequency by ΔTs to the sampling circuits 31, 32, and 42.

  As described above, the strobe signal S4 is slightly shifted in frequency by ΔTs from the waveform obtained by simply dividing the synchronous clock signal S2, but the predetermined phase relationship, for example, the zero cross point coincides. The data for one period until the next matching is called a frame, and the matching time is called the head of the frame. The head of the frame may be set to the reference time ts0.

  On the other hand, the frequency conversion circuit 36 outputs a strobe signal S5 obtained by dividing the frequency of the synchronous clock signal S2 (for example, about 1/1000) to the sampling circuits 33 and 43.

  Then, the sampling circuit 31 samples the signal under measurement S1 every time ts0 to ts6 based on the strobe signal S4, and outputs the sampling result to the waveform generation means 38 as the vertical axis information signal S3.

  Further, the sampling circuit 32 samples the reference signal S6 every time ts0 to ts6 based on the strobe signal S4, and outputs the sampling result to the time base calculation means 37 as a reference signal S7.

  Further, the sampling circuit 33 samples the reference signal S6 every time tr0 to tr3 based on the strobe signal S5, and outputs the sampling result to the time base calculation means 37 as a reference signal S8.

  Further, the sampling circuit 42 starts sampling the cosine wave reference signal S 10 by the strobe signal S 4, and outputs a reference signal S 11 as a sampling result to the time base calculation means 37. That is, the sine wave reference signal S6 and the cosine wave reference signal S10 are simultaneously sampled by the sampling circuits 31, 32, and 42 based on the strobe signal S4.

  On the other hand, the sampling circuit 43 starts sampling the cosine wave reference signal S10 by the strobe signal S5, and outputs the reference signal S12 of the sampling result to the time base calculation means 37. That is, the sine wave reference signal S6 and the cosine wave reference signal S10 are simultaneously sampled by the sampling circuits 33 and 43 based on the strobe signal S5.

  Then, the time base calculation means 37 selects either the set of reference signals S7 and S8 obtained by sampling the sine wave reference signal S6 or the set of reference signals S11 and S12 obtained by sampling the cosine wave reference signal S10, and the reference The phase at which sampling was performed in the signal S6 or the reference signal S10 is calculated, and the horizontal axis information signal S9 used at the sampling time is output.

  That is, in both the sine wave and the cosine wave, the signal slew rate is small in the vicinity of the maximum value and the minimum value of the amplitude, and it may be difficult to accurately obtain the phase from the amplitude. Therefore, a set of sampling points having a large slew rate is used.

  This will be specifically described with reference to FIG. FIG. 3 is a diagram showing the timing for sampling the reference signals S6 and S10. In FIG. 3, the horizontal axis is time and the vertical axis is amplitude. Also, the point where the sine wave reference signal S6 crosses zero is set to 0, and is shown for one period. Note that sampling is performed every π / 8.

  The time base calculation means 37 does not select sampling points included in the unused area, but selects sampling points with a large signal slew rate. Sampling points P1 to P3 select a sampling value obtained by sampling the reference signal S6, sampling points P4 to P7 select a sampling value obtained by sampling the reference signal S11, and a sampling point P9 selects a sampling value obtained by sampling the reference signal S6. To do.

  In an ideal orthogonal state, that is, when the phase is shifted by 90 degrees (π / 2), a sine wave with an initial phase of zero and a cosine wave with an initial phase of 90 degrees are sampled, and π / 4, 3π / 4, 5π / 4. By switching the reference signals S6 and S11 selected at 7π / 4, the signal slew rate can be kept larger.

  Note that the sampling value of the other reference signal S10 may be used as the sampling point P3, and the sampling point P8 may be used instead of the sampling point P7.

  Here, it is assumed that the reference signals S7 and S8 are selected. The time base calculation unit 37 calculates the sampling time and the resolution ΔTs for each of the samplings ts0 to ts6 from the reference signals S7 and S8 and the correction data in the correction data storage unit 46, and outputs them to the waveform generation unit 38. The detailed operation of the time base calculation unit 37 will be described later.

  Further, the waveform generation means 38 generates and reproduces the waveform of the signal under measurement S1 from the amplitude of the vertical axis information signal S3 of the sampling circuit 31 and the sampling resolution ΔTs of the horizontal axis information signal S9 of the time base calculation means 37, and displays it. The waveform is displayed on the means 39 or the waveform is stored in the storage means 40.

Next, jitter will be described.
The jitter includes the jitter of the synchronous clock signal S2 itself from the outside of the oscilloscope Osi (hereinafter referred to as Jr) and the jitter of the reference signal S6 output from the reference signal generation circuit 34 (hereinafter referred to as Jf).

  Jr is transmitted to the vertical axis information signal S3 output from the sampling circuit 31 as the phase fluctuation of the signal under test S1 that is synchronized.

  The Jr of the synchronous clock signal S2 is also transmitted to the strobe signal S4 via the frequency conversion circuit 35. However, only the jitter of the frequency component limited by the band of the frequency conversion circuit 35 is obtained. Therefore, since the jitter of the strobe signal S4 is different from Jr, the jitter of the strobe signal S4 is hereinafter referred to as Js. Of course, Js includes some jitter components of Jr. Further, since the sampling circuit 31 performs sampling with the strobe signal S4, Js is transmitted to the amplitude of the vertical axis information signal S3 as the fluctuation of the sampling timing of the sampling circuit 31.

  However, when the sampling circuit 31 samples the signal under measurement S1 having the Jr phase fluctuation with the strobe signal S4 having the same Jr phase fluctuation (that is, when no jitter occurs in the frequency conversion circuit 35), Jr cancels out. Will not affect sampling. From this, when the sampling circuit 31 samples the signal under test S1 including Jr with the strobe signal S4 including Js, they act in the direction of cancellation, and hence the jitter of the vertical axis information signal S3 is expressed as Jr-s. To do. Note that the minus sign does not mean a mathematical subtraction and conceptually represents the difference between jitters (Jr and Js).

  Jf is transmitted to the reference signals S7, S8, S11, and S12 as phase fluctuations of the sampling values in both of the sampling circuits 32, 33, 42, and 43. The sampling circuits 32 and 42 sample based on the strobe signal S4 including Js. The sampling circuits 33 and 43 sample based on the strobe signal S5 including Jr.

  Accordingly, Js is transmitted to the reference signals S7 and S11 as fluctuations in sampling timing in the sampling circuits 32 and 42. As described above, since Js acts in the direction to cancel Jf, the jitter of the reference signals S7 and S11 is hereinafter referred to as Jf-s. The meaning of the minus sign is the same as described above. Jf-s is transmitted to the horizontal axis information signal S9 for the purpose of correcting Js of the strobe signal S4.

  On the other hand, Jr is transmitted to the strobe signal S5 through the frequency conversion circuit 36, and is transmitted to the reference signals S8 and S12 as fluctuations in the sampling timing of the sampling circuits 33 and 43. Since Jr acts in the direction to cancel Jf as described above, the jitter of the reference signals S8 and S12 is hereinafter referred to as Jf-r. The meaning of the minus sign is the same as described above. Jf-r is transmitted to the horizontal axis information signal S9 for the purpose of correcting the jitter Jr of the synchronous clock signal S2.

  Jf is canceled when the time base calculation means 37 calculates the difference between Jf−r and Jf−s and disappears. Since the absolute value of the amplitude of the reference signal S6 or S10 becomes zero by obtaining the difference between the reference signals S7 and S8 or the reference signals S11 and S12, only the jitter component Js-r or Jr-s of the strobe signals S4 and S5 is extracted. Is done. The meaning of the minus sign is the same as described above. Depending on whether the calculation here is Js-r or Jr-s, the correction method in the subsequent waveform generation means 38 changes.

  Then, the waveform generation means 38 combines the vertical axis information signal S3 including the fluctuation Jr-s due to Jr and Js with the horizontal axis information signal S9 including the phase fluctuation Js-r or Jr-s due to Jr and Js. To compensate for the effects of jitter. Thereby, accurate sampling times ts0 to ts6 can be obtained.

  As described above, the reference signal generation circuit 34, the sampling circuits 32, 33, 42, 43, and the time base calculation unit 37 in FIG. 1 obtain the correction amount of jitter (Js-r or Jr-s). .

  Next, operations of the sampling circuits 32 and 33, the time base calculation unit 37, and the waveform generation unit 38 will be described with reference to the flowchart of FIG. The reference signal of the reference signal generation circuit 34 will be described as an example of a sine wave whose frequency is known and waveform distortion is small. An example in which the reference signals S7 and S8 are selected will be described.

  The sampling circuits 32 and 33 sample the reference signal and output the reference signals S7 and S8 to the time base calculation means 37 (ST1).

  Then, the time base calculation means 37 converts the sampling values of the reference signals S7 and S8 into the phase of the standard signal S6. For example, if the reference signal S6 is a sine wave, it is obtained from an inverse trigonometric function. Then, the obtained phase is corrected using the correction data (ST2).

  Further, the time base calculation unit 37 obtains the phase change from the sampling point at the previous sampling for the phase of the sampling point obtained in step ST2. Since the previous sampling point is the sampling time ts0 at the beginning of the measurement frame or the accurate sampling time ts1 to ts6 after correcting the jitter, the phase displacement from there includes the jitter at the current sampling point ( ST3).

  Then, the time base calculation unit 37 obtains a difference between the phase displacement obtained from the reference signal S7 and the phase displacement obtained from the reference signal S8, calculates the difference time (time axis information) by converting the difference phase, It outputs to the waveform generation means 38. In addition to the jitter component Js-r or Jr-s, the difference time includes a difference Ts-Tr in sampling intervals of the strobe signals S4 and S5, that is, ΔTs in FIG. 2 (ST4).

  Then, the waveform generation means 38 adds the difference time obtained in step ST4 to the previous sampling time and matches the amplitude of the vertical axis information signal S3 of the sampling circuit 31. As a result, all jitter at the current sampling point is removed, and the current sampling point is corrected to an accurate sampling time (ST5).

  Further, the waveform generation means 38 outputs the waveform reproduced at the sampling time corrected in step ST5 to the display means 39 and the storage means 40 (ST6).

Next, an operation when acquiring correction data will be described.
If the reference signal generation circuit 34, the sampling circuits 32, 33, 42, 43, the phase adjustment circuit 41, and the frequency conversion circuits 35, 36 are ideal circuits, jitter on the time axis can be removed as described above. Therefore, correction data is not necessary, but in reality, each of the circuits 32 to 36 and 41 to 43 includes errors (for example, nonlinearity, amplitude (including distortion) error, offset error, delay error, orthogonality error, etc.). Jitter is generated.

  The modulation signal generation circuit 44 modulates the reference signal S6 of the reference signal generation circuit and samples only the same phase point (same amplitude point) or limited phase point (amplitude point) of the modulated reference signals S6 and S10. Modulation is performed so that there is no problem. That is, the modulation is performed so that the ratio of the frequency of the strobe signals S4 and S5 to the frequency of the reference signals S6 and S10 is not an integer that is divisible by the first decimal place.

  For example, the modulation signal generation circuit 44 applies phase modulation or frequency modulation using a random frequency signal having a wideband frequency component. This eliminates the restriction on the phase points to be sampled. Alternatively, if the ratio of the frequencies of the strobe signals S4 and S5 to the frequencies of the reference signals S6 and S10 is finer than being divisible by the first decimal place instead of an integer, a signal having a predetermined frequency instead of a random frequency is used. In this case, phase modulation or frequency modulation may be applied.

  The sampling circuits 32 and 33 sample the modulated sinusoidal reference signal S6 based on the strobe signals S4 and S5, and output the reference signals S7 and S8 to the time base calculation means 37. Also, the sampling circuits 42 and 43 sample the modulated reference signal S10 that has been converted to a cosine wave by the phase adjustment circuit 41 based on the strobe signals S4 and S5, and output the reference signals S11 and S12 to the time base calculation means 37. To do.

  Then, as in step ST 2 described above, the time base calculation unit 37 obtains the phase and outputs it to the correction data calculation unit 45.

  Note that the time base calculation means 37 determines whether the relationship between the frequencies of the reference signals S6 and S10 and the strobe signals S7 and S8 is measured at a wide range of phase points (amplitude points). If the phase data (phase obtained in step ST2 described above) is confirmed and a wide range of phase points cannot be measured, the correction data calculation means 45 causes the modulation signal generation circuit 44 to change the frequency of the signal to be modulated. .

  If a wide range of phase points are obtained, the correction data calculation unit 45 calculates correction data from the phase data of the time base calculation unit 37. An example will be described.

  Note that the data pair (phase) obtained by sampling the reference signal (cosine wave) S10 and the reference signal (sine wave) S6 simultaneously by the sampling circuits 42 and 32 using the strobe signal S4 is {DBcos (n), DAsin (n)}. And Here, n is an integer indicating the sampling order. DBcos (n) is data obtained by sampling the reference signal S10 by the sampling circuit 42. Further, the range of DBcos (n)} and DAsin (n) is assumed to be a positive / negative value with a central value of 0 for the sake of simplicity.

  Here, FIG. 5 is a diagram in which simultaneously sampled data pairs {DBcos (n), DAsin (n)} are plotted on a plane having DBcos and DAsin as two axes. FIG. 6 is a plot of FIG. 5 with time on the horizontal axis and amplitude on the vertical axis.

  Since the error of each circuit 32 to 36 and 41 to 43 is included, the circle in which the data pair is plotted (hereinafter referred to as a correction data circle) is not a perfect circle as shown in FIG. , Roughly a collection of points on the circumference.

  The correction data calculation means 45 obtains a perfect circle by the least square method from the data pairs that are plotted as shown in FIG. Then, the correction data calculation means 45 obtains a difference in each phase between the point on the perfect circle that can be regarded as having no error and the data pair on the correction data circle for each data pair.

  For example, the point of the data pair {DBcos (1), DAsin (1)} is used as a reference whose phase angle difference from the perfect circle is “0”, and the relative phase angle difference of each data pair with respect to this reference is determined. I will ask. A correction value Δθab (n) corresponding to the phase angle θab (n) corresponding to each data pair {DBcos (n), DAsin (n)} is obtained, and a table of the obtained phase angle θab and correction value Δθab is used as the correction data. Store in the storage means 46.

  Similarly, a reference signal (cosine wave) S10 and a reference signal (sine wave) S6 are sampled by a sampling circuit 43, 33 and a data pair (phase) simultaneously sampled by a strobe signal S5 {DDcos (m), DCsin (m) }. Here, m is an integer indicating the sampling order. Further, DDCos (m) is data obtained by sampling the reference signal S10 by the sampling circuit 43.

  Then, the correction data calculation means 45 obtains a perfect circle from the data pair by the least square method. Then, the correction data calculation means 45 obtains a difference in each phase between the point on the perfect circle that can be regarded as having no error and the data pair on the correction data circle for each data pair. Further, a correction value Δθcd (m) corresponding to the phase angle θcd (m) corresponding to each obtained data pair {DDcos (m), DCsin (m)} is obtained, and a table of the obtained phase angle θcd and correction value Δθcd is obtained. Is stored in the correction data storage means 46. Here, FIG. 7 shows an example of correction data stored in the correction data storage means.

Here, θab (n) = tan ⁻¹ {DBcos (n) / DAsin (n)}, and 0 ° ≦ θab (i) ≦ 360 °. Also, θcd (m) = tan ⁻¹ {DDcos (m) / DCsin (m)}, and 0 ° ≦ θcd (i) ≦ 360 °.

An operation in which the time base calculation means 37 performs correction when actually measuring the signal under measurement S1 will be described. In the above-described step ST2, the time base calculation means 37 converts the sampling values of the reference signals S7 and S8 into the phase of the reference signal S6. A data pair {DABcos (k), DAAsin (k)} (DABcos (k) is sampled by the sampling circuit 42 and DAAsin (k) is sampled with the reference signal S11 sampled simultaneously with the reference signal S7. The phase angle θdab (k) (= tan ⁻¹ {DABcos (k) / DAAsin (k)}) is obtained from the data sampled by the sampling circuit 32. Further, the time base calculation unit 37 searches the table of the correction data storage unit 46 for θab (p) closest to the phase angle θdab (k), and correction data for the phase angle difference corresponding to the searched θab (p). Δθab (p) is added to the phase obtained from the sampling signal S7 and corrected.

Similarly, a data pair {DADcos (j), DACsin (j)} with the reference signal S12 sampled at the same time as the reference signal S8 (DADcos (j) is sampled by the sampling circuit 43, and DACsin (k) is The phase angle θdcd (j) (= tan ⁻¹ {DAD cos (j) / DACsin (j)}) is obtained from the data sampled by the sampling circuit 33. Further, the time base calculation unit 37 searches the table of the correction data storage unit 46 for θcd (q) that is closest to the phase angle θadd (j), and correction data for the phase angle difference corresponding to the searched θcd (q). Δθcd (q) is added to the phase obtained from the sampling signal S8 and corrected.

  Of course, the modulation signal generating circuit 44 does not modulate the reference signal S6 when measuring S1 of the signal under measurement. I, j, k, p, and q are integers.

  As described above, the reference signal generation circuit 34 outputs the high-quality reference signal S6 with known frequency and amplitude and less waveform distortion. Then, the sampling circuits 32, 32, 42, 43 sample the reference signals S6, S10 with the strobe signals S4, S5 obtained by converting the synchronous clock signal S2, and the time base calculation means 37 is used to store the sampling value and correction data storage means. The sampling time of the signal under measurement S1 is obtained from the correction data. On the other hand, in the case of obtaining correction data, the modulation signal generation circuit 44 performs phase modulation or frequency modulation on the reference signal S6. As a result, the ratio of the frequency of the strobe signals S4 and S5 having a predetermined frequency relationship with the synchronous clock signal S2 from the device under test 10 to the frequency of the reference signal of the reference signal generating circuit 34 is an integer or about the first decimal place. Even if the value can be divided by, the data obtained by sampling the reference signals S6 and S10 with the strobe signals S4 and S5 may be sampled only at the same phase point or a limited phase point of the reference signals S6 and S10. A wide range of phase points is sampled. Therefore, even if the frequency of the clock signal synchronized with the signal under measurement is unknown or the waveform quality is poor, correction data for a wide range of phase points can be acquired without being affected by the clock signal. In other words, no matter what device 10 is used by the user, jitter correction corresponding to aging, temperature change, etc. can be performed when desired, and correction data can be obtained with high accuracy. The waveform display of few oscilloscopes can be performed.

[Second Embodiment]
FIG. 8 is a block diagram showing a second embodiment of the present invention. Here, the same components as those in FIG. In FIG. 8, modulation signal generation circuits 47 and 48 are provided instead of the modulation signal generation circuit 44.

  The modulation signal generation circuit 47 modulates the strobe signal S4 output from the frequency conversion circuit 35, and the modulation signal generation circuit 48 modulates the strobe signal S5 output from the frequency conversion circuit 36. It should be noted that the modulation is not performed when the signal under measurement S1 is measured, but is performed when correction data for correction is obtained. Similarly to the modulation signal generation circuit 44, the modulation signal generation circuits 47 and 48 perform phase modulation or frequency modulation using a random frequency signal having a broadband frequency component or an arbitrary frequency signal. Of course, the amplitudes of the strobe signals S4 and S5 are not modulated.

  The operation of such an apparatus will be described. The measurement of the signal under measurement is the same as the apparatus shown in FIG. When acquiring correction data, the modulation signal generation circuits 47 and 48 modulate the strobe signals S4 and S5, and only the same phase point (same amplitude point) or limited phase point (amplitude point) of the reference signals S6 and S10. Is modulated so that no sampling occurs. That is, the modulation is performed so that the ratio of the frequency of the strobe signals S4 and S5 to the frequency of the reference signals S6 and S10 is not an integer that is divisible by the first decimal place.

  For example, the modulation signal generation circuits 47 and 48 apply phase modulation or frequency modulation to the strobe signals S4 and S5 using a random frequency signal having a wideband frequency component. This eliminates the restriction on the phase points to be sampled. Alternatively, if the ratio of the frequencies of the strobe signals S4 and S5 to the frequencies of the reference signals S6 and S10 is finer than being divisible by the first decimal place instead of an integer, a signal having a predetermined frequency instead of a random frequency is used. Thus, phase modulation or frequency modulation may be applied to the strobe signals S4 and S5.

  As in the apparatus shown in FIG. 1, the correction data calculation means 45 obtains new correction data from the phase obtained by the time base calculation means 37, and the obtained correction data is stored in the correction data storage means 46. Store.

  In this way, the reference signal generation circuit 34 outputs the reference signal S6 with known frequency and amplitude and less waveform distortion. Then, the sampling circuits 32, 33, 42, 43 sample the reference signals S6, S10 with the strobe signals S4, S5 obtained by converting the synchronous clock signal S2, and the time base calculation means 37 is used to store the sampling value and correction data storage means. The sampling time of the signal under measurement S1 is obtained from the correction data. On the other hand, in the case of obtaining correction data, each of the modulation signal generation circuits 47 and 48 performs phase modulation or frequency modulation on the strobe signals S4 and S5. As a result, the ratio of the frequency of the strobe signals S4 and S5 having a predetermined frequency relationship with the synchronous clock signal S2 from the device under test 10 to the frequency of the reference signal of the reference signal generating circuit 34 is an integer or about the first decimal place. Even if the value is divisible by or the waveform quality is poor, the data obtained by sampling the reference signals S6 and S10 with the strobe signals S4 and S5 is only the same phase point or limited phase point of the reference signals S6 and S10. A wide range of phase points are sampled without being sampled. Therefore, even if the frequency of the clock signal synchronized with the signal under measurement is unknown, correction data for a wide range of phase points can be acquired without being affected by the clock signal. In other words, no matter what device 10 is used by the user, jitter correction corresponding to aging, temperature change, etc. can be performed when desired, and correction data can be obtained with high accuracy. The waveform display of few oscilloscopes can be performed.

The present invention is not limited to this, and may be as shown below.
In the apparatus shown in FIG. 1, the modulation signal generation circuit 44 performs frequency modulation or phase modulation on the reference signal S6 of the reference signal generation circuit 34. However, the modulation signal generation circuit 44 is not provided, and the reference signal generation circuit 44 is not provided. 34 may be capable of changing the frequency of the reference signal S6 to a desired frequency. Of course, the frequency is varied within a range where the waveform is distorted and the amplitude does not change. As in FIG. 1, when the correction data calculation means 45 calculates the correction data, the reference signal generation circuit 34 has a ratio between the frequency of the reference signal S6 and the frequencies of the strobe signals S4, S5 as an integer or a decimal first. The frequency is changed in accordance with an instruction from the correction data calculation means 45 so that the value is not divisible by the digit. Then, the correction data calculation means 45 obtains correction data from the phase obtained by the time base calculation means and stores it in the correction data storage means 46.

  In the apparatus shown in FIG. 1 and FIG. 8, the configuration in which the present invention is applied to the sampling oscilloscope Osi is shown. However, the present invention may be applied to other measurement apparatuses, for example, a jitter measurement apparatus such as a time interval analyzer.

  In the apparatus shown in FIGS. 1 and 8, the signal under test S1 and the synchronous clock signal S2 output from the device under test 10 may be electrical signals or optical signals. The output signals of the frequency conversion circuits 35 and 36, the sampling circuits 31 to 31, and the like. The input / output signals 33, 42, and 43 may be electric signals or optical signals, and signals suitable for signals may be used. Further, it may be a physical quantity other than electricity or light.

It is the block diagram which showed the 1st Example of this invention. FIG. 2 is a sampling timing diagram of the apparatus shown in FIG. 1. FIG. 4 is a timing diagram of sampling of the sampling circuits 32 and. It is a flowchart explaining operation | movement of the apparatus shown in FIG. It is the figure which plotted the data pair and perfect circle which were sampled simultaneously on the plane which makes DBcos and DAsin 2 axes. FIG. 5 is a diagram in which time is plotted on the horizontal axis and amplitude is plotted on the vertical axis. It is the figure which showed an example of the correction data of the correction data storage means. It is the block diagram which showed the 2nd Example of this invention. It is the figure which showed the structure of the conventional sampling oscilloscope.

Explanation of symbols

31-33, 42, 43 Sampling circuit 34 Reference signal generation circuit 35, 36 Frequency conversion circuit 37 Time base calculation means 38 Waveform generation means 41 Phase adjustment circuit 44, 47, 48 Modulation signal generation circuit 45 Correction data calculation means 46 Correction data Storage means

Claims (6)

In a sampling device that repeatedly samples a signal under measurement,
A sampling circuit for a signal under measurement for sampling the signal under measurement;
A reference signal generating circuit for outputting a reference signal having a known frequency;
A sampling circuit that samples the reference signal of the reference signal generation circuit;
A frequency conversion circuit for generating a strobe signal for starting sampling by the sampling circuit and the signal under measurement sampling circuit from a clock signal synchronized with the signal under measurement;
Correction data storage means for storing correction data for correcting measurement errors;
A time base calculating means for obtaining a phase from a sampling value of the sampling circuit, correcting the obtained phase with the correction data of the correction data storage means, and obtaining time axis information of the sampling circuit for the signal under measurement;
Correction data calculation means for obtaining the correction data from the phase of the time base calculation means and storing the correction data in the correction data storage means;
A sampling apparatus, comprising: a modulation signal generation circuit for frequency-modulating or phase-modulating a reference signal of the reference signal generation circuit. In a sampling device that repeatedly samples a signal under measurement,
A sampling circuit for a signal under measurement for sampling the signal under measurement;
A reference signal generating circuit for outputting a reference signal having a known frequency;
A sampling circuit that samples the reference signal of the reference signal generation circuit;
A frequency conversion circuit for generating a strobe signal for starting sampling by the sampling circuit and the signal under measurement sampling circuit from a clock signal synchronized with the signal under measurement;
Correction data storage means for storing correction data for correcting measurement errors;
A time base calculating means for obtaining a phase from a sampling value of the sampling circuit, correcting the obtained phase with the correction data of the correction data storage means, and obtaining time axis information of the sampling circuit for the signal under measurement;
Correction data calculation means for obtaining the correction data from the phase of the time base calculation means and storing the correction data in the correction data storage means;
A sampling apparatus comprising: a modulation signal generation circuit for frequency-modulating or phase-modulating the strobe signal of the frequency conversion circuit.   3. The sampling apparatus according to claim 1, wherein the modulation signal generation circuit performs frequency modulation or phase modulation when the correction data calculation means calculates correction data.   4. The modulation signal generating circuit performs frequency modulation or phase modulation so that a ratio between the frequency of the reference signal and the frequency of the strobe signal does not become a value that is divisible by an integer or a decimal first place. The sampling device according to any one of the above. In a sampling device that repeatedly samples a signal under measurement,
A sampling circuit for a signal under measurement for sampling the signal under measurement;
A reference signal generation circuit that outputs a reference signal with a known frequency and has a variable frequency;
A sampling circuit that samples the reference signal of the reference signal generation circuit;
A frequency conversion circuit for generating a strobe signal for starting sampling by the sampling circuit and the signal under measurement sampling circuit from a clock signal synchronized with the signal under measurement;
Correction data storage means for storing correction data for correcting measurement errors;
A time base calculating means for obtaining a phase from a sampling value of the sampling circuit, correcting the obtained phase with the correction data of the correction data storage means, and obtaining time axis information of the sampling circuit for the signal under measurement;
Correction data calculation means for obtaining the correction data from the phase of the time base calculation means and storing the correction data in the correction data storage means;
A sampling apparatus characterized by comprising: When the correction data calculation means calculates correction data, the reference signal generation circuit changes the frequency so that the ratio between the frequency of the reference signal and the frequency of the strobe signal does not become a value that is divisible by an integer or a first decimal place. The sampling apparatus according to claim 5, wherein

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