SU1226318A1 - Method of stroboscopic conversion of periodic alternating voltage - Google Patents

Abstract

The invention relates to the field of electrical measurements and can be used in the emission of fast-variable processes. The purpose of the invention is to improve the accuracy of the conversion. The device contains an amplifier Yay / G |: U:. agra} shchntel 1, controlled dividers 2 and 3 frequencies with variable division ratio of single-band frequency converter 4, quartz oscillator 5, oscillator 6 strobe-1-1MpulsoB, stroboscopic mixer 7, amplifier 8 low frequency and band-pass filter 9. Introduction of operation summing the divided frequencies of the converted voltage and the voltage of the reference oscillator with the subsequent use of the voltage of the received frequency Hz msh reduces the range of variation of the converted frequency during the reorganization of the converted hour Ota. The introduction of the summation operation with an equal division factor ensures the synchronous division of the indicated frequencies, gives the constancy of the converted frequency with the frequency stability of the reference oscillator, 1 iet, s "3 v / k. Fnp

Description

one

The invention relates to electrical measurements, in particular to the field of stroboscopic measurements, and can be used in the emission of rapidly varying processes,

The purpose of the invention is to improve the conversion accuracy by reducing the effect of the output myiMOB conversion by decreasing the range of variation of the converted frequency when the frequency is tuned.

The essence of the method is that after dividing the frequency of a periodic alternating transformable voltage by a factor m (ni is a positive integer greater than I) equal to the number of periods of alternating transformable voltage in the gating period and determined by the frequency range of alternating voltage summarize the frequency of the variable transformable voltage with the frequency of the voltage, the frequency of which is divided by the frequency of the reference oscillator by the same factor. Introducing the operation of summing the divided convertible voltage of the reference oscillator followed by using the voltage of the resulting frequency for gating reduces the range of variation of the converted frequency when the frequency is tuned. Introducing the operation of summing the divided frequencies of the alternating voltage to be converted and the voltage of the reference oscillator at an equal division factor, which is ensured by a synchronous (i.e., equal) division of the indicated frequencies, gives the converted frequency with the frequency stability of the reference oscillator. This allows narrowing the bandwidth to the output of the stroboscopic converter, which makes it possible to install a filter with a nice bandwidth (determined only by the waveform) at the output of the stroboscopic converter and thereby reduce the level of zigums.

The frequency summing operation (algebraic, which also includes obtaining the frequency difference) can be a heterodyne transform, a single-band transform (implemented, for example, in a 174XA7 chip) 5

moshyu continuous phase rotation, summation in the ring PAL,

The drawing shows a stroboscopic conversion device implementing the proposed method.

The stroboscopic converter consists of a limiting amplifier 1, controlled frequency dividers 2 and 3 with a variable division factor, a single-band frequency converter A, a quartz oscillator 5, a strobe pulse generator 6, a stroboscopic mixer 7, a low frequency amplifier 8, a bandpass filter 9 In this case, the device input is connected to the inputs of the Stroboscopic mixer 7 and the amplifier-limiter 1, the output of which is connected to the first input of a single-band converter through the first controlled divider 2 frequency 4 frequencies, to the second input of which the output of the crystal oscillator 5 is connected via the second controlled divider 3 frequencies, the output of the single-band converter 4 frequencies through the generator 6 of the strobe pulses connected to the inputs of the reference signal of the stroboscopic mixer is connected to the input of the bandpass filter 9, the output of which is the output of the device. The control inputs of dividers 2 and 3 are frequency: connected to control COD13 buses.

The limiting amplifier is a conventional limiting amplifier, the gain factor and the limiting level are chosen such that the output voltage is sufficient to trigger subsequent frequency dividers with Controlled dividers 2 and 3 frequencies to be conventional digital dividers with variable Nm division factor. The magnitude of the division factor comes in a digital code from external devices. Dividers can be dividers on meters of type 155IE7, Divider 2 can be executed on 193 series microchips the output filters to highlight the main harmonic. A single band 4 frequency converter is, for example, a 174XA7 chip or another single sideband frequency conversion device. Quartz ge31

The oscillator 5 is a conventional crystal oscillator with an output voltage, for example, logic levels. The strobe pulse generator is a conventional peaking generator with simultaneous generation of different polarity pulses. The stroboscopic mixer is a conventional strobe mixer, for example, with a bridge diode. Amplifier 8 is a conventional low-frequency amplifier, for example, on a 544UD2 microcircuit. Filter 9 is a low-pass bandpass filter.

The device works as follows.

Periodic voltage U of frequency ff is amplified and limited by amplifier 1. From the output of the limiter amplifier, standard-shaped pulses are sent to a controlled frequency divider 2, at which the division factor t is set by external signals. The divider output voltage

---. Managed divider 3 frequency m

gives the output voltage

p png p output frequency

m

crystal oscillator 5. A single band frequency converter outputs a differential voltage at the output

fc fnfi

m

m

The strobe pulse generator 6 from the voltage of the received frequency generates short opposite-polarity pulses simultaneously arriving at the stroboscopic mixer 7. The stroboscopic mixer 7 gates the variable periodic voltage U. applied to it. The strobing pulses and remembers the voltage at the time of strobing. Amplifier 8 amplifies samples of the memorized voltage. Band-pass filter 9 separates the frequency envelope, limiting the noise band of the output transformed voltage.

Let us consider in more detail the operation of the device.

Since the input signal is periodic with a period T, it can be written in general form as a function of the argument about, t

and f (u, t) f (- | --t),

L, if

where is MC 21Tf.

(one)

263184

The voltage And at the output of the stroboscopic mixer can be written as

5 and K, f (. T „. К), (2)

where T is the period of discrete samples determined by Kotelnikov's theory; 10 K - 0.1.2,.,.;

K - coefficient transmission at

gating.

Since expression (2) is a periodic function, 15 it can be written as

U,

 K, f (tT,) to, (3)

where m is any integer, in our case equal to the coefficient of division dt m

The frequency of gating pulses at the strobe pulse generator 6 is written as

25 f - E - E e

m

(four)

where m is the frequency division factor.

From the formula (4) can be obtained, replacing 30 n frequency periods, the expression

one

one

Shopping center

(five)

from where

TP -

Jlln

T -pr

(6)

Substituting expression (6) into (3), we get

„Kf - | i- (-1 | 1 .-) to.

 L J-c -J

 K, f (inp

P T „-K).

(7)

Since the conditions of Kotelnikov's sampling theorem are fulfilled, after amplification at the output of the bandpass filter 9, we have the voltage Ug, which we obtain, replacing discrete time samples with the current time t, taking into account the transmission coefficient

i.i. K, K f (t)

55

K, f (),

(eight)

where CL is the gain of the amplifier and filter j

K K - Pr 2iiFf, p.

S122

Similarly, it can be shown that the repetition period of the voltage Ug is equal to

T

-etc

-etc

Comparing equation (1) and (8), IMD, that the voltage and shape coincides with the transformed voltage, but has a transformed frequency that does not depend on the change in the input frequency Wj. ZlTf,. In the case of single-band converter A

frequency

f m

EE.L

m

that

The discharge (8) changes its sign, i.e., the input and output voltages pr) are single-phase. It can also be similarly shown that if the division factor Ffip is one more time than the division factor of the frequency of the transformed voltage f, then the Xth harmonic voltage of the input voltage is distinguished at the output Pf by the output voltage. nonlinear distortion of the input signal in the case, for example, if the input signal has the form of a sinusoid. The resulting expressions can also be obtained by a more rigorous method using spectral methods,

The choice of the division factor .tn is most simply solved if the frequency f ..- is known a priori. Then, for example, with the selected range of variation of f. 1-2 MHz for the frequency range f 2-4 MHz, the division ratio should be increased. for f-4-6 MHz, the division factor is m 3, and so on. The division factor for the selected band is chosen to be constant and no tuning or measuring manual operations are required. Strobe converter is fully automatic. The division factor can also be selected by sequential division in the automatic mode of the frequency of the input transform. A.Shishkin Editor

Compiled by N. Mikhalev Tehred L. Oleinik

Order 2125/42

Circulation 728 Subscription

VNIIPI USSR State Committee

for inventions and discoveries 13035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, Projecto st., 4.

,

0

.five

0

five

0

five

186

This voltage is followed by comparing the result of dividing the frequency comparator with the reference frequency value. If the comparison is positive, the required value of the coefficient m is given.

From consideration of formula (8), it can be seen that the frequency of the output transformed voltage does not depend on the frequency of the input voltage and is equal to ffjp — the output frequency of the quartz oscillator. By installing a narrow-band filter, it is possible to significantly narrow the output noise band and, accordingly, to improve the conversion accuracy, for example, by phase shift.

Claims (1)

Invention Formula A stroboscopic transformation method of a periodic alternating voltage with a time-scale transformation, consisting of strobing — pulses synchronized with the transformed voltage, storing instantaneous values of the alternating voltage at the moment of strobing time, and the low frequency frequency of with the formation of gating moments by dividing the frequency of the input alternating voltage by a factor m equal to the number of periods of alternating voltage in the period gating clothing, where the number is an integer greater than 1 and determined by the frequency range of the alternating voltage, characterized in that, in order to increase the conversion accuracy, a reference frequency is generated equal to the selected envelope frequency of the converted low-frequency voltage, divided by a factor t, c are combined with the divided frequency of the variable voltage being converted, and from the voltage of the obtained frequency they form strobe pulses in terms of duration and amplitude. Corrector C, Cherni