SU567147A1 - Apparatus for measuring non-linear distortion factor - Google Patents

Description

I

The invention relates to information measuring technology and can be used to measure the nonlinear distortion coefficient (AIS) of infra-low frequency signals.

A non-linear distortion factor meter 1 is known. It is an analog measuring instrument of a compensating type, containing operating voltmeters, first and higher harmonics, a comparison device, a device for searching and selecting a minimum voltage, a control unit, a fundamental frequency compensating voltage generating unit consisting of serially connected discrete frequency multiplier, discrete voltage divider, discrete phase shifter, code-voltage converter and logometer.

However, the performance of such a SOI meter is low, it is determined by the algorithm for searching and minimizing the effective value of the differential voltage at the output of the comparison device, which in turn depends on the required measurement accuracy of the SOI and therefore, at a sufficiently high measurement accuracy, it can be about 20 -40 periods of the signal under study, which at an infra-low frequency of the order of IQ-Hz is 50 hours or more. In addition, this SOI meter does not accurately measure the CII of signals containing a constant component.

The purpose of the invention is to increase the speed and accuracy of measuring the nonlinear distortion coefficient of signals containing a constant component.

This is achieved by including a control unit, a comparator, a device for searching and isolating the minimum voltage, a logometer, AND elements, a memory device, a discrete compensating signal shaping unit, an actual value calculator, an indicator and a converter in the nonlinear distortion meter. analog-cad, the first input of which through the first element I is connected to the input width of the meter, the second input of the analog-code converter. is connected to the first output of the control unit, per the primary input of which is connected to the input width of the meter, and the output of the converter; the analogue code is connected to the first inputs of the comparison device and the memory device, the second and third inputs of the last are connected to the second

and the fourth output of the control unit, the output of the memory device is connected to the second input of the comparator, the third input of which is connected to the fourth output of the control unit, and the fourth input of the comparison device to the output of the formed discrete compensating signal whose inputs are connected respectively to the second output of the unit control and the first output of the search and highlight device, the second output of which is connected to the second input of the control unit, and the inputs of the search and highlight device Connected to the fifth output of the control unit and the first output of the actual value calculator, the inputs of which are connected to the output of the comparison device and the third output of the control unit, respectively, and the second output of the effective value calculator are connected to the serially connected logometer and indicator, the second inputs of the elements And they are connected respectively to the generous and fourth outputs of the control unit. The drawing shows the block diagram of the proposed meter SOI. The meter contains a control unit 1, an AND 2 element, an analog-code converter 3, a memory device 4, a discrete compensating signal generating unit 5, an AND 6 element, an indicator 7, a device 8 and a low voltage voltage detector, a comparison device 9, a calculator 10 effective values and a logometer 11. It is known that the square of the effective value of a continuous periodic signal and (a) is determined by the expression (/ g J and (a) + + + ul ... In the digital method of measuring the effective value of the same apr w (a ) the whole period of its measurement T - split at equal points P. At the dividing points of the period o2, ..., a, -, - .., using an analog-code converter, the instantaneous values of the signal under study are measured u (ai), "(02), ..., u (ai), ..., "(ap). These values are squared by the digital device and summed. As a result, an approximate effective value of the same signal is determined and (a) is numerically (-Lp if the spectrum of the periodic The signal and (a) do not contain harmonics, the order of which is higher than / C, then when equality (2) is exact (Kotelnikov theorem). But it is necessary to measure the SOI of a periodic non-sinusoidal signal "(a) infra-low frequencies from ten to Hz, which is the ratio of the effective value of the higher harmonics of the signal and (a) the effective value of the first harmonic 1 / | .; / 2 This ratio calculates the digital logometer. The accuracy and speed of the measurement of SOI depends on how the measurement of the integral quantities L / V.G and Ui is organized. The above shows that the well-known high-precision compensation method with analogue waveform at infra-low frequencies requires a long measurement time. This is due to the fact that the compensating sinusoidal signal must have the same frequency as the signal under study, and one period is required for each step in the compensation process. In order to fully compensate the first harmonic of the signal s (a) in amplitude and phase, it may take a decade or more steps, each of which takes a period of the signal under study. The proposed meter is distinguished by the fact that the first harmonic of the signal under investigation is unknown in amplitude and phase and (a) is compensated in discrete carts at discrete values of the compensating signal at the corresponding points. In other words, the compensating signal is a sinusoidal sinusoidal function of the fixed frequency biko w, the initial phase ifiKOM and the amplitude UITTIKOM of which can be changed schag behind schagom in the process of compensation. The influence of the constant component of the signal and (a) is eliminated before the compensation process begins. For this, in the first period, and (a) discrete values of u (ai), u (a2), ... (dcr) are simultaneously fed to the memory device and the comparison device. The device 9 records the average value and (a) for the per-iodine, which is saved and subtracted at the corresponding moments of time from the values of p (a) in the compensation process. The schematic solution of the comparison device can be implemented as a digital device consisting of a reversible counter into which the discrete values u (ai) of the signal under investigation are recorded during the first period and by means of algebraic addition the mean value and (a) over the period (constant component), and it is maintained throughout the entire time of the transformed; a register in which the following operations are performed: the discrete values of the signal under investigation "(a,) from the memory device and the result of the subtraction and (a.d) and the average t / o value stored in the reversible counter are recorded alternately, i.e. The action of the constant component is taken into account in this way, and then the com (a) value is subtracted from the result of subtracting each value (ui) - C / o. The result is fed to the computational unit 10. Thus, the constant component of the signal in the further transformations is no longer involved. If at the first stage of the compensation compensation module step by step only the initial phase of the compensating grating sinusoid is changed at its amplitude t / imb-oM, then the device will automatically determine the minimum value of the function & {yl N - c / level sin (Schoi / + I 1 +, “-) r} WHHff.,“ Oi.). where u (ai) are the instantaneous values of the signal under study at points a, -, measured and recorded in the memory cells in the preceding -period. In the language of the analog measurement method, the expression (4) means that the first harmonic of the signal and (n) 710 phase are compensated. After reaching the minimum of the function (4) When compensating for the phase of the device, the automatic search for the minimum of the function (4) searches for the minimum. If only the amplitude of the compensating signal f iniKOM is changed at a constant value of the initial phase corresponding to the minimum of the function (4. As a result, the minimum value of FUNCTION ( 4) when compensating for the first harmonic of the signal under study, s (a) in both phase and amplitude, this minimum is equal to the square of the effective value of all higher harmonics. (A /) - C / Ko sinX g / nB, 1, 1 tmKOH - con IX ("Ko" # g - I hggkogugo-, xx. F / ,; "0") i / lr- (5) The device for finding the minimum of the function (4) is based on a numerical comparison of the successive .x values of this function F (iJ) iKOM) obtained in the calculator 10 for each period / 2 "com of the compensating voltage with a discrete change - f com from period to period. If on the 5th compensation period, the values of r {ch com and F (- (JIKOM) have Vfcon 3 values on the period (S-fl) values), and the inequality f5 + 1 ps holds for the next step (period on The frequency of the Ucom) compensation is set by ,, n T L VliCOK flKOM AND - The phase compensation process ends in step L if HepaBeHCTBa pN -... is performed. After condition (6) is satisfied, the amplitude compensation time in step L1 is reached: The number of steps (periods - |, necessary for full compensations in phase and amplitude, can be significant, as with analogue compensation method, but the duration of one step equal to peT - can be made hundreds and thousands of times shorter than the step duration with an analog compensation method of the duration of the 2 period of the signal under study / -). The schematic solution of the device for searching and selecting a minimum can be implemented, for example, as a digital device of three registers and AND elements, which allow the control unit to subtract the subsequent number from the previous one, reset the previous one, rewrite the subsequent one to the previous register, and A new value is written to the previous register, which comes from the actual value calculator. The sign of the indicated subtraction operations sets the direction of the next step in phase or amplitude. 2g. The duration of the period 7icon is a discrete compensating sinusoidal signal, during which P values of the compensating sinusoid at the points aiKo.M, 02 com, ajKOM, ..., 2Pnom are set, does not depend on the signal period, but is determined only by the speed of digital or counting elements) localization of the formation of a discrete compensating signal and digital computational nodes defining the functions (4) and (5). In this case, the reduction in the measurement time of SOI by the proposed device in comparison with the known analog device is equal to the frequency ratio com / com O) / i.e., if Hz and Hz, then the gain in time / JH 10pa3 is obtained. / 10 Hz. Modern specialized digital computing devices allow to calculate individual values of functions (4) and (5) during the time of the GCOM, 01 s. The second important advantage of the proposed device is that the block of forming a discrete compensating signal produces discrete values of the sinusoidal signal t / i7n: KOMsin ((OKo.4..i4-il5iKOM) at the points-комkom., Digital; 50y .. form: high

the degree of accuracy determined only by the number of bits of the computing device of this block. This provides an increase in the accuracy of measuring SOIs at infra-low frequencies. The application of the well-known analogue compensation method for measuring SOIs at infra-low frequencies encounters considerable fineness not only because of the large measurement time, but also because of the difficulty of forming a continuous compensating signal with a small SOI value.

The principle of the proposed meter is as follows.

In the initial state, the memory device 4 is cleared, the resolving potentials H / 1, f / .i are not fed from control unit 1 to the elements I 2, 6, and zero is fixed on the indicator 7. If both the 2 and the control block 1 control the signal under test and the inputs (and after pressing the OVCK button in block 1, at the moment of the signal transition and (a) through the zero value of the block 1, the control voltage develops (/ which, the input of the SECOND input element AND 2. passes the signal under study to the first input of converter 3. The converter at points o.- defined by block 1 (PULS L / j begins to generate discrete values of the signal "(s;) Number of discrete workings Ca,), obtained at the output of the converter 3, for the period the signal under study is equal to the NUMBER of pulses generated by the block L Each discrete value of the signal under study u (ni) is written into its cell of the memory device 4. At the end of the T1er.iod T of the signal under study, block I removes the resolving potential f / i from the SECOND input element I 2. From this point on, the signal and fa) to the converter 3 is not received and the supply of PULSES Ui to the converter 3 is stopped. The process of recording samples of the signal under investigation "(a ,;) into the device 4-ti ends. After the termination of the first period of the signal under study, unit 1 begins to generate pulses U; ro, with a frequency of cell-PM E-co, which are received from the memory of device 4 of the memory, sending it, synchronously with them, to the corresponding discrete values in DEVICE 9 comparison (aO, u (az), ..., u (ai}, .... and (ap} is alternately; but where the C / p. component is recorded from these discrete values fixed in the device 9) is performed. At the same time, the pulses f /, Ko: .r are fed to the input of the device 5, which creates moments of formation of discrete compensations signaling signals

"Con (" /) t Koi Sin (+).

".I | /" /.

which, as well as the discrete values of the signal under study, with a certain delay, enters the device 9 comparisons:. As a result of the cmiepauHft carried out in this device, the signal arriving alternately

CARE SPECIFICATIONS 10 S B1): HCHA-STROGI.tg-orazneni. has the appearance

“(A,) r / (x,) - f /, .o„ (,);

and (7,) Гц (7j) - U, - «, .о„ (7з);

and (a,) a (-1 - f / o - com ();

and (and (7,) and, - H, o "f7p),

where and (a, -) is the result of a sequential

subtraction from discrete signal values

"(" :) constant component Uo and discrete values of the compensating signal

1-PM (the calculator 10 calculates the effective value of the function y (a, -) for the period

y Jr i «wi-.

(eight)

After the end of the first period of the compensating signal, the control unit 1 generates a control pulse Uz, which enables the device 8 for searching and minimizing.

As soon as the device 8 receives the effective value of the voltage from the calculator 10, the process of minimizing the function (4) in phase begins. After finding the minimum in phase, the minimum of the function (4) is searched by amplitude. Minimum search

in phase and amplitude is carried out by the device 8 according to the algorithm indicated above, by changing the discrete values of the phase Qc and the amplitude f / i of such a compensating voltage until

the condition of full compensation in accordance with expressions (6) and (7) and b). „.: f / im,

ijl kom.

Upon reaching full compensation, the device 8 transmits via block 1 with a pulse L

the readings of the calculator 10 through the block 1 with a pulse t / 3 transmit the readings of the calculator 10 through the element I 6 "and the first input of the logometer 11. The same pulse prevents the memory device 4 from outputting discrete values

(a, -) of the signal under study, and a reversible counter in the comparison device 9 to perform a subtraction operation. Thus, the discrete values of the compensating signal coming from the output of the block 5 pass to the input of the calculator 10, the output of which receives the current value of the first harmonic for the period of the compensating voltage:

. -1 / 5 G “koiG,

and, and

(9)

Claims (1)

which, through the element 6 and if there is an impulse f / s 65 n |) at the second input, also passes to the input of the logometer 11. The division 11, the division on jpauiiH division.: acs: -1 and 6c. , on Ll, gives the value of the nonlinear distortion coefficient, which is fixed by the indicator 7, A- - / С, - -fj- The use of new nodes provides an increase in the speed of measuring SOI of periodic signals, which is significant at ultra-low frequencies, as well as improving the accuracy of measuring SOI signals, containing a constant compiled yush.uyu. Claims The non-linear distortion coefficient meter comprising a control unit, a comparison device, a voltage minimum voltage search and separation device, a logometer, characterized in that, in order to improve the speed and accuracy of measurement of the nonlinear distortion factor of signals containing a constant component, elements I, memory device, discrete compensating signal generating unit, effective value calculator, indicator and analog-code converter, first input Which is through the first element and is connected to the input bus of the meter, the second input of the analog-code converter is connected to the first output of the control unit, the first input of which is connected to the input bus of the meter, and the output pgeobr: caller analog-stake, village: ns.g; with the first and inputs of the device cpaBtjeHii :; and a memory device, the second and third inputs of the terminal are connected to the second and fourth outputs of the control unit, the output of the memory device is connected to the second input of the comparison device, the third input of which is connected to the fourth output of the control unit, and the fourth input of the comparison device to the output of the unit forming a discrete compensating signal, the inputs of which are connected respectively to the second output of the control unit and the first output of the search and highlight device, the second output of which is connected to the second at the input of the control unit, and the inputs of the search and highlight device are connected to the fifth output of the control unit and the first output of the actual value calculator, the inputs of which are connected to the output of the comparison device and the third output of the control unit, respectively, and the second output of the effective value calculator through the second element I is connected to serially connected logometer and indicator, with the second inputs of elements AND connected to the sixth and fourth outputs of the control unit, respectively. Sources of information taken into account in the examination 1. USSR author's certificate L 370540, cl. with 0.1 R 23/16, 1973.