JPS5873877A - Sampling method for repeated waveform - Google Patents

Abstract

PURPOSE:To obtain a sampling method having an excellent linearity and requiring little time for conversion, by using two frequency dividers with constant mutual relations. CONSTITUTION:The period of a pulse generator 11 is T, and frequency dividers 12 and 13 divides the frequency of the output of the generator and deliver outputs having periods of NT and MT respectively. In this connection, a resolution determining to what extent a repeated waveform is resolved is denoted by T, while the number of all data of the waveform to be found finally is denoted by N. A time MT of repeated operation of a sample hold circuit 6 is limited by the velocity of operation of an A/D converter, and the formulaIis set between M and N. When the resolution T=0.1mus and N=4095, for instance, M>= 50 on condition that MT>=5mus, and thus M=2<6>=64. Accordingly, a time for conversion turns to be very short, i.e. MNT=26ms. At the same time, since a repetition period and a sampling period are obtained from the output of frequency devision, an error in the time interval of sampling is decided by the stability of a reference frequency employed by the pulse generator 11, and thus it can be made not more than 0.01% by using a conventional quartz oscillator.

Description

DETAILED DESCRIPTION OF THE INVENTION 111 Technical Field of the Invention The present invention relates to a method in which a waveform is repeatedly broken down into small pieces on the time axis and sampled.

(2) Prior Art A block diagram of the conventional method is shown in FIG. In the figure, 1 is a pulse generator, 2 is a sawtooth wave generator, 3 is a staircase wave generator, 4 is a voltage comparator that compares the output of sawtooth wave generator 2 and the output of staircase wave generator 5, and 5 is a voltage comparator that compares the output of sawtooth wave generator 2 with the output of staircase wave generator 5. The circuit under test, 6, is a sample and hold circuit.

Next, an example of the waveform shown in FIG. 1 is shown in FIG. 2. In the figure, T1 is the period of the repetitive waveform W1, Pl represents the first sampling point, and Pl represents the sampling point of the next waveform W2. Now, the period Tt = 409.5 μs, and the points P1 and P
The time interval T2 of 2 is set to 409.6 μs. Similarly, if the time interval T5 between points P2 and P3 is set to 4096 μS, the waveform W becomes 409.6 us-409
, 5ps=α1μs resolution.

FIG. 1 shows the waveform W1. of FIG. 2. W2-... to point P
This is a configuration diagram for sampling I, Pl, . . . , and the output of the circuit under test 5 has the waveform W + in FIG.
It becomes W 2.

Among the outputs of the pulse generator 1, one passes through the circuit under test 5 and enters the sample-and-hold circuit 6, the other one enters the sawtooth wave generator 2, and the other one enters the staircase wave generator 5.

The sawtooth 9-wave generator 2 is synchronized with the pulse generator 1 and has a period T
The step wave generator 5 also generates a step wave synchronized with the pulse generator 1. The voltage comparator 4 compares the outputs of the sawtooth wave generator 2 and the staircase wave generator 5, and converts the sawtooth wave output to points P1, F2=, . . . in FIG.・ is sent to the side sample hold circuit 6.

The ramp hold circuit 61d samples the response of the circuit under test 5 at points P1, P2, . . . 1@.

The output of the sample and hold circuit 6 is AL) (not shown). 1f! from the device to a CRT, etc.

(61 Problems with the Prior Art) The accuracy of the time intervals for points P1, P2, etc. in Figure 2 is determined by the linearity of the sawtooth wave. It is difficult to obtain a sawtooth wave with α1% or less, resulting in a sampling error.

Furthermore, the sample methods shown in FIGS. 1 and 2 have a problem in that the conversion time is long. For example, if the waveform repetition period T+ = 409.5 μs and the resolution α1 μs as shown in Figure 2, the total number of data will be 4095, and the conversion time will be 409.
5 x 409.5 μS = 1,68 g.

(4) Purpose of the Invention The present invention provides a sampling method with good linearity and short conversion time by using two frequency dividers that have a certain relationship with each other.

(Examples of 51 inventions A block diagram of an embodiment according to the present invention is shown in FIG.

In the figure, 11 is a pulse generator that outputs pulses with a repetition period T, 12 is a branching unit that divides the output of the pulse generator 11 and outputs an output with a repetition period NT, and 15 is a pulse generator 11.
This is a frequency divider that divides the output of MT and outputs an output with a sampling period MT.

Here, T is the resolution that determines how far to decompose the repetitive waveform, and N is the total number of data of the waveform to be finally obtained. HetoT is given as a condition in advance.

Further, MT is the repetitive operation time of the sample and hold circuit 6, and since an AD converter is normally connected after the sample and hold circuit 6, the value of MT is limited by the operation speed of this AD converter.

The following relationship is set between M and N.

N=MxK-A・・・・・・・・・・・・・・・・・・
・・・・・・・・・(Here, A, M, and N are integers, A≧1, K=constant, and set the values of M and N so that N7M is not an integer. .Formula (al to N
>M.

Next, an example of the waveform shown in FIG. 5 is shown in FIG. Waveform W in the figure
u, W+2 are the output waveforms of the circuit under test 5 and the repetition period is NT. Pll is the first sampling point, Pll is the next sampling point, and the points PH and PI
The time interval of 2 becomes M T. That is, in FIG. 4, the output of the pulse generator 11 is divided by the frequency divider 12 to form a waveform W++.
, W+2, . Then, the waveform W++ is sampled at points P++, Pll, . . . , and the next waveform W12 is further sampled. In this case, the first sampling point P 101 of the waveform WI2 is located at a position not only AxT in equation 1al but also from the point PM of the waveform W + 1.

This is because N7M is not an integer, so if the repetition period NT is sampled at the sampling period MT, only AT will protrude, and the sampling points of waveform W+t and waveform W+2 will be n.

Note that although A=1 in formula 1al is usually used, A>1 may also be used.

Next, a numerical example of FIG. 5 will be shown. In order to keep the conditions the same as those in Figures 1 and 2, resolution T = α1 ps, N = 40
95.

As described above, the value of MT is limited by the conversion time of the subsequent AD converter, and is usually MT≧5 μs.

Since T=[L 1 μs, M≧50. Since M is the frequency division ratio, set M=26=64.

Transforming the formula (at).

K=(N+A)7M・・・・・・・・・・・・+
b1 formula (If you put N=4095%A=1 and M=64 into bl, then K=2'=64.

The conversion time according to FIGS. 3 and 4 is given by MxNxT. Therefore, M=6a, N=4095°T=α1μ
s, the conversion time is the product of these, 26m5, and the first
The conversion time is much shorter than the conversion time of 1.68 seconds in the case of FIG.

+61 Effects of the Invention According to the present invention, the conversion time is shorter than that of the conventional method, and the sampling time interval error is reduced by the pulse generator 1.1 because the conversion time is obtained from the repetition period and the sampling period fully divided output. It is determined by the stability of the reference frequency used, and can be reduced to 0.014 or less by using an ordinary crystal oscillator.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional method. FIG. 2 is an example of the waveform according to FIG. 1, FIG. 5 is a configuration diagram of an embodiment according to the present invention, and FIG.
Graphical waveform diagram. 1... Pulse generator, 2... Saw 9
Wave generator, 5... Staircase wave generator, 4...
Voltage comparator, 5...Circuit under test, 6...
・Sample and hold circuit, 11...Pulse generator that outputs an output with a repetition period T, 12...A divider that outputs an output with a repetition period NT, 13...Sample A frequency divider that outputs a periodic MT output. Agent Patent Attorney Kinji Omata 1.7 9th Sen No. 4 Hayabusa

Claims (1)

[Claims] 1. A pulse generator with a repetition period T, a first frequency divider that outputs an output with a repetition period NT from the output of this pulse generator, and a sample period MT from the output of this pulse generator. and a 20th frequency divider that outputs the output. and a sample hold circuit which takes the output of the first frequency divider as the first input via the path to be measured (9) and takes the output of the second frequency divider as the second input. N=MxK-A, where A, M and N are fireflies, respectively, A≧1, K=constant, and setting the values of M and N so that N7M is not an integer is called a % value. Sample period of the repeating waveform.