SU1203699A1 - Method and apparatus for measuring dynamic conversion characteristics of high-speed and high-precision analog-to-digital converters - Google Patents

Abstract

1, A method for measuring the dynamic conversion characteristics of high-speed and high-precision analog-to-digital converters, which consists in summing two test signals with different rate of change applied to the test analog-digital converter, generating the main clock signals when the rapidly changing test signal passes through the reference level, and forms a code proportional to the sum of two test signals, and comparing this code with a given code at the time of post the main clock signals, the formation of a slowly varying signal from the comparison, the measurement of the average code, the slowly changing test signal of the test signal, characterized in that, in order to improve the accuracy, when comparing the codes, the code of the corresponding reference level is used as the specified code The code of the average value of the slowly changing test signal, the value of the reference level is changed until the code is equal. the measured average value — a slowly varying test signal to a given reference level code, at the point of transition through the reference level, the rapidly changing test signal determines the magnitude and sign of its derivative, forms an auxiliary sequence of clock pulses with its synchronization with the main clock signals, and code, proportional to the sum of the two test signals on the subsequent conversion cycles, is performed at the moments of arrival of the auxiliary sequence The timing of the clock signals, the measured code of the average value of the slowly varying test signal, corresponding to a certain value of the derivative of the rapidly varying signal, is used as a parameter of the dynamic characteristic of the tested A / D converter. 2, A device for measuring the dynamic conversion characteristics of high-speed and high-precision analog-to-digital converters, comprising a fast-varying test signal shaping unit, a slowly varying test-i forming unit (L С IND about 00 a co

Description

one

the signal, the output of which is connected to the first input of an analog adder, the output of which is connected to the initial output bus, the first input of the digital code comparison block is connected to the input bus, the second input is connected to the first output of the code specifier unit, the output of the digital code comparison block is connected to the input of the forming unit a slowly varying test signal, a digital integrating voltmeter, characterized in that, in order to improve the accuracy, a threshold level setting block, a threshold level fixing block, a comparator block are introduced into it Ator, time meter, synchronized pulse generator, the output of the block forming a rapidly varying test signal connected directly to the second input of the analog adder and to the first input

the house of the comparators block, the second and third inputs of which are connected to the first and second outputs of the threshold level setting block, the fourth input through the threshold level fixing block is connected to the third output of the threshold levels block, and the first and second outputs are connected to the corresponding time meter inputs, and the third is connected to the first input of a synchronized pulse generator, the second, the input of which is connected to the second output of the code setting unit, and the first and second outputs are connected to the second th output line and the third input of the digital comparator block codes, respectively, forming the output unit slowly varying test signal connected to the input of the digital integrator voltmet - ra.

The invention relates to digital measurement technology and can be used to measure the dynamic characteristics of high-speed and high-precision analog-digital converters in network measuring systems, their metrological certification in a dynamic mode.

The purpose of the invention is to improve the measurement accuracy of the dynamic conversion characteristic of analog-to-digital converters.

Figure 1 shows the timing diagram illustrating the proposed method; Fig. 2 is a functional diagram of the device for implementing the proposed method.

The diagrams (Fig. 1) show a rapidly varying test signal 1, a slowly varying test signal 7. signal 3, equal to the sum of the signals 1 and 2 applied to the input of the analog-digital converter under test; the reference signal 4 corresponding to the selected point of the conversion characteristic; generated discrimination signal 5

the transition of signal 1 through a predetermined threshold level UQ, corresponding to the selected value of signal 1, the resultant comparison signal 6; 7 discrimination signals, corresponding to transitions, signal 1 through a threshold level changed relatively to Uo and when determining the magnitude and sign of the derived signal 1 in

point A, the discrimination signals 8, corresponding to the transitions of the signal 1 through the changeable threshold level C relative to Uo (

auxiliary sequence of digital signals 9; signals Yu, obtained by synchronizing signals 8 by a sequence of signals 9; a sequence of signals 11, ill) strides the actual sampling times of the sum of the test signals 3J of points A, B of the transition of signal 1 through the threshold level UQ, in which the derivative has

different size and sign; the average value of the signal 2; point G of signal 3, corresponding to the moment of action of signal 5, delayed by

3

The delay delay To, u, n of the reference of the analog-digital converter J is the time interval (between signals 5 and 7, the conversion time Tcp of the test analog-digital converter j the period of the signal T is 1.

A diagram of the device (Fig. 2) shows a block 12 of forming a rapidly varying test signal; a unit 13 for forming a slowly measuring: test signal; analog adder 14, test analog-to-digital converter (A1SCH-) 15; digital block 16 comparison codes; block 17 task codes; digital integrate a 11D1 voltmeter 18; threshold level setting unit 19, threshold level fixing unit 20; block 21 comparators; meter

22 time interval, synchronized pulse generator 23; the first 24 and the second 25 output buses and the input bus 26.

As block 12, any periodic signal generator with a stable repetition frequency and an arbitrary shape can be used. As block 13, as in the known device, an analog voltage integrator controlled by a bipolar voltage switch can be used, the control input of which is the input of block 13. As block 17, a block similar to the block of setting codes in the known device containing an additional trigger (bit) of the register for writing codes whose output is an additional block of the block 17. Three block 21 (according to the number of levels UQ; 11 (1; UfuHn) of the same comparator, summing the inputs which are connected together and are the input of block 21. The subtractive inputs of the first and second comparators are connected directly to the first and second outputs of block 19, and the subtractive input of the third comparator is connected via block 20 to the third output of block 19. The subtractive inputs of the comparators are first, second and the third control inputs of the unit 21, and its outputs are the outputs of the respective comparators. As a synchronized generator

23 pulses used generator with external start.

036994

The implementation of the proposed method is carried out as follows.

A rapidly changing signal 1 is formed (Fig. 1), necessary and sufficient for which the periodicity and long-term frequency stability 1 / t are sufficient conditions. A signal 2 is formed, the time constant of which is changed

0 changes within two

A number of selected points of the conversion (quantum) characteristic is set equal to the formation time of not less than several tens of signal 1 periods.

The sum of 3 signals 1 and 2 serves. to the entrance of the test A1CT. Simultaneously with the summation of signals 1 and 2 form a signal 5, which can

2Q Corresponding to any selected value of signal 1. For ease of consideration, FIG. 1 shows the threshold DO,. equal to zero and corresponding to zero values

25 of signal 1 at points A and B, and also shows signal 5, exactly (without delay) corresponding to point A of signal 1, where the derivative has a positive

on, since the waveform 1 is different from sinusoidal, although its average value is zero.

The output signal of the test object, representing the current result of the analog-to-digital conversion

signal 3, at the moments of action of signals 5, is compared with the reference signal 4 equal to the specified threshold level DO 0. When comparing the current result of the analog-to-digital conversion of signal 3, equal to the instantaneous value of signal 3 at the time of the action of signal 5 (Fig. 1) is represented by a digital encoded signal with the corresponding numerical

by value. The reference signal 4, equal to zero, is also represented by a digital signal, with a numerical value equal, i.e. with zero. VO code of all bits.

By means of the resultant signal 6, comparing the reference signal 4 and the current result of converting the signal 3, the signal 2 is generated as follows. If the result

analog-to-digital conversion of signal 3 at the time of action of signal 5 is equal to signal 4, then signal 6 changes from a low level5

Into the high state, as a result of which signal 2 begins to increase. If the result of converting signal 3 is greater than signal 4, then signal 6 changes to a low state, and signal 2 begins to fall. The described process is repeated many times, with signal 2 oscillating relative to a predetermined reference signal 4, which in this case is equal to a predetermined threshold level.

In accordance with the method of comparison, the average value of the signal 2 is measured. Since the signal 4 is set equal, the average value of the signal 2 should also be numerically equal. The difference between er and magnitude is the smaller, the more precisely the equality between the instantaneous values of signals 3 and 4 compared at the moments of action of signals 5 is fulfilled.

Since the real test A1Sch has a delay of the count, the value of which is not known in advance, the actual value of signal 3 corresponds to the point which is determined by the moment of action of signal 5 delayed by T (xi, because of the difference between the values of synal 3 at points A and G is formed signal 2, the mean value of which differs from zero by the difference in the values of signal 3 at points a and g. I

Then, according to the method, the value of the threshold level is changed by the discrimination signal with respect to the predetermined threshold level to Uh. As a result, signals 7 are formed that correspond to transitions of signal 1 — through the threshold level and. According to the magnitude of the time interval i, the magnitude and sign of the deviation of the level Ut, from UQ, the magnitude and sign are determined by the call at the transition point of signal 1 or the given threshold level U. In order to formalize the determination of the magnitude and sign of the derivative, it is assumed that Lh has a conditionally negative sign if signal 5 is delayed relative to signal 7, and positive if signal 7 is delayed relative to signal 5, the magnitudes of the prog levels {J and Uo are algebraically subtracted from them signs, and

the magnitude and sign of the derivative is determined, KaK 3lJ / dt i-Uh -Uo (thH for point A (Fig. 1) is equal to dU / dtt-Un-0 / - / J-) The magnitude of the changes in the threshold level (J), relative to U, limited by the permissible methodical error of linear approximation of signal 1 at point A. Given the above formal rule, the magnitude and sign of the derivative can be determined at any point of signal 1, for example B.

With a further change in the threshold level, its modified

5, the value of UT J J, when the signal 2 measured from the mean value B is equal to 2, the value of the specified threshold level Uo The fixed value of Otachl corresponds to signals 8, which

0 ahead of time signals 5 by the value of Tu, u, n. In this case, the actual moments of comparing the result of the signal conversion 3 with the reference signal 4 equal to the specified level

5 о 0, exactly correspond to points A of signal 1, the value of signal 1 in which is equal (Jo, and the magnitude and sign of the derivative are determined.

In accordance with the one-way method, with the fixation of the ig cp, one form an auxiliary sequence of digital signals 9, the repetition period of which should be a large Kli equal to Tpr and a multiple of the period; At signal 1. Synchronize signals 9 with signals 8. As a result of synchronization, one of signals 9 is periodically matched with signals 8 and signals 10 are received.

“This ensures accurate

U

Snap-phase signals 10 with signals 8 and signal 3, i.e. the location of any of the signals 10 with respect to signal 3 becomes accurately known. 5

After the signals 9 are synchronized with the signals 8, the signal 3 is sampled by the signals 10 used by the -dl gating of the subject

ADC. As a result of performing the considered operations of the method, the actual sampling times of the signal 3 correspond to the signals 11, at the moments of comparison of the output signal s5 n; 1 l of the test object with the reference signal correspond to the signals 5. Since the signals 11 (fig.O correspond to different values of the signal 3 in

Since the signals of the signal 5, and the signals 5 always correspond to the same values of the signal 3 at point A, then taking into account the known value — the sign of the derivative at point A and the period of TPR signals 11 — the exact test conditions correspond to the measured dynamic characteristic transform. Simultaneously with the actual sampling of the signal 3 at the moments of action of the signal 11, the output signals of the ADC under test are actually compared with the reference signals 4, corresponding to the selected points of its reproduction characteristics. Thus, when measured, real conditions of the test object are provided taking into account the effect of both the magnitude and sign of the derivative, and the transient processes of establishing therein when converting different values of the signal 3.

The influence of these factors during the formation of signal 2 leads to deviations of the average values of signal 2 from the reference signals 4 corresponding to the selected points of the conversion characteristic. The deviations are related to the fact that the values of the result of the signal 3 conversion at points A at the moments of comparison are distinguished from the actual values due to the test transducer's inability to react correctly at all points of the conversion characteristic by the given value (sign) of the test signal 3 when gating A1 А with the given TPD.

By choosing the frequency and amplitude of signal 1, as well as the repetition period of TPD signals 9, it is possible to widely vary the initial conditions for measuring the dynamic characteristics of the transform, corresponding to the values of these parameters. In this case, by assigning all or only selected points of the characteristic, by setting the corresponding reference signals 4 by the deviations from them of the average values formed in the process of measuring signals 2, one can judge the whole or individual

areas of the dynamic characteristic of the transform, control the occurrence of deviations equal or greater than permissible.

with y and 20 25 and 40

35

55

The device works in the following way.

The output signal of the block 12 is fed to the adder 14 together with the signal 2 from the output of the block 13. The total signal 3 from the output of the adder 14 is fed to the input of the subject. At the same time, the output signal 1 of block 12 is fed to the input of block 21.

From the output of block 19, which 1} represents the source of stable voltages, threshold levels are set corresponding to UQ, t) n and itc, o, n. The values of Up and Un are set constant, and the threshold level at the third output changes until the value is fixed by block 20 representing any fixed voltage regulator, for example, a graduated potentiometer whose position is fixed by the operator when the voltage level changes. Pulse signals 5 and 7 from the first and second outputs of block 21 are fed to the inputs of the time meter 22, and from the third output, signals 8 are fed to the input of the synchronized generator 23. With a logic signal with a low level (logic O), fed to the input control of the generator 23 from the output of block 17, the synchronized generator is turned off and the pulse signals from the third output of the meter 22 pass through the generator 23 to the gate inputs of the A / D converter 15 and the block 16 of the comparison.

At the entrance of the test ADC 15 operates with the total signal 3 (figure 1). At the time of sampling the ADC 15, the instantaneous value of the voltage of the signal 3 at its input is equal to the current value of the voltage of the signal 2 at the output of block 13. Let the input block 16 from the output of block 17 be given a code that is numerically equal to UQ. If the output code of the A / D converter 15, obtained by gating, is equal when comparing the code from the output of block 17, the resulting signal 6 from the output of block 16 controls block 13 so that the output voltage of block 13 starts to increase. When it reaches the value at which. the output code of the test A1Sh 15 exceeds the code set in block 17, the output signal 6 of block 16 controls

 unit 13 so that the voltage at its output begins to decrease.

By changing the value of the threshold level at the third input of block 21, the pulses are shifted in phase at the third output of block 21 relative to the signals from the code of block 12, and the average voltage at the output of block 13 is measured using a digital integrating -voltmeter 18. When the measured average value the voltage of signal 2 at block 13 becomes equal to that of level 19 installed at block 1 and the input of block 21, the voltage level US, 5 fixes the level of voltage at the third input of block 21 at: block 20 received. After the third output of block 21 f ) pulses 8 (FIGHT, defining exactly the result of the conversion / SCP 15 signal position 3 at Point A are taken into account, taking into account the compensation of the effect of the distance from signal 3 in this and its envelope) at the established Iko Un () voltage of the first and second outputs of the I9 unit and the in-interval in interval measured by the 22-meter-time intgr) hall. In this case, the values of - Un and UQ are algebraically interpreted with their signs., And for L (, a negative sign is conventionally accepted if the signal 5 is determined by the signal 7 ,, and positive 9 if the signal is 7 the delayed signal relative to the signal 5 The meter 22 to the outputs of the block 21 of the angle S. is easily detected by the measurement result either directly of the value of L in the first case, or of the value of 5 DF-T, - is the period of signal 1 (Fig. 1). point A (fig „1) is equal to dU / (: it -Un-C / -tvi UH (Lj ,.

When the logical signal at the control input of the synchronized generator 23 changes to a state with a high level (logical 1), it is switched on in the self-oscillatory mode. In this case, the generator 23 is synchronized by pulses.

8, operation with its own pulse repetition period 9 — Tf, p selected as a multiple of the pulse repetition period TC 8. At the first output 5 of the generator 23 connected to the gate input of the A / D converter 15, pulses 10 operate, and at the second output connected to the input gating unit 16, - pulses 8,

10 As a result, testing of A1SCh 15 at time points (pulses 11, fig. 1) corresponding to different voltage values of signal 3 at the output of sum 15 of torus 14 is provided. At the same time, signal formation 2 at the output of block 13 is controlled only at moments comparisons (signal 5, FIG. 1), when the instantaneous values of voltage

The 20 output of the block 13 must be equal to M1 by the specific voltage values at the input of the tested A / D converter 15.

The average value of the output voltage of the block 13 is measured over a large number of cycles of its change by a digital integrating voltmeter 18. The digital measurement result corresponds to the transition boundary from one quantum to another

30 characterization of the conversion of the test ALI 15. The deviation of the digital measurement result (average value B) from the code (reference signal 45 of FIG. 1) specified from the first

The output of block 17 to the second input of block 16 ,, characterizes the error of the dynamic characteristic of the conversion at this point. The error exactly corresponds to a certain value and the sign of the derivative and a given Tpr.

After the operator registers the measurement result in block 17, the task of codes sets the code corresponding to 45 corresponding to the value of the following

points of the measured conversion characteristic. The measurements are repeated at constant code values at the second output of block 17, the threshold

50 levels of voltage UQ, (In, iti, p at the inputs of block 21 and the constant value of the TPD to obtain complete information about all points of the conversion characteristics of the tested ADC.

FIG. one

Claims (2)

1. A method for measuring the dynamic conversion characteristics of high-speed and high-precision analog-to-digital converters, which consists in summing up two test signals with different rates of change applied to the tested analog-to-digital converter, generating basic clock signals when the fast-changing test signal passes through the reference level, and generating a code proportional to the sum of two test signals, and comparing this code with a given code at the time of receipt of the main clock signals, the formation of a slowly changing signal according to the results of comparison, measuring the code of the average value of the slowly changing test signal, characterized in that, in order to improve accuracy, when comparing the codes, the code of the corresponding reference level is used as the set code after measuring the code of the average value of slowly changing test signal, the value of the reference level is changed until the code is equal. measured average values of a slowly varying test signal to a given reference level code, at the point of transition through the reference level of a rapidly changing test signal, determine the value and sign of its derivative, form an auxiliary sequence of clock pulses with 18 synchronization with the main clock signals, and the formation of a code proportional to the sum of two test signals at subsequent conversion clocks, carried out at the moments of receipt of auxiliary sequentially five clock signals measured code slowly varying mean value of the test signal corresponding to the determined value of the derivative of a rapidly changing signal used as the dynamic characteristic parameter of the test analog-digital converter. 2. A device for measuring the dynamic conversion characteristics of high-speed and high-precision analog-to-digital converters, comprising a unit for generating a rapidly changing test signal, a unit for generating a slowly changing test SU „., 1203699 signal, the output of which is connected to the first input of the analog adder, the output of which is connected to the first output bus, the first input of the digital code comparison unit is connected to the input bus, the second input is with the first output of the code setting unit, the output of the digital code comparison unit A digital integrating voltmeter is connected to the input of the unit for generating a slowly varying test signal, characterized in that, in order to improve accuracy, a threshold level setting unit, a threshold level fixing unit, and a block are introduced into it comparators, a time interval meter, a synchronized pulse generator, and the output of the rapidly changing test signal generating unit is connected directly to the second input of the analog adder and to the first input of the comparator unit, the second and third inputs of which are connected directly to the first and second outputs of the threshold level setting unit, the fourth input through the threshold level fixation unit is connected to the third output of the threshold level setting unit, and the first and second outputs are connected to the corresponding inputs of the time interval meter, and the third is connected to the first input of the synchronized pulse generator, the second is the input of which is connected to the second output of the code setting unit, and the first and second outputs are connected to the second output bus and the third input of the digital code comparison unit, respectively, the output of the formation unit slowly changing test signal. connected to. input of a digital integrating voltmeter.