SU1626174A1 - Method for determining the frequency of sine signals - Google Patents

Abstract

The invention relates to electrical and radio measurements. The aim of the invention is to improve the accuracy of frequency determination. The method of determining the frequency of a sinusoidal signal consists of forming two mutually orthogonal signals from the input signal, measuring three instantaneous values of each of these signals at reference time intervals, with the measurement moment of the third MI of one of the mutually orthogonal signals coinciding with the measurement of the first instantaneous value of the other . A formula is given for determining the signal frequency, and a device for implementing the method is also described. The formation of mutually orthogonal signals and their subsequent processing made it possible to increase the exact frequency of the signal in a time shorter than its half-period. 1 il. (L

Description

The invention relates to electro-radio measurements and can be used to determine a frequency in a time shorter than a half period.

The aim of the invention is to improve the accuracy.

The essence of the method for determining the frequency of a sinusoidal signal is as follows.

An additional sinusoidal signal is formed from the input sinusoidal signal, which is orthogonal with respect to the input sinusoidal signal, i.e. together they form a system of mutually orthogonal sinusoidal signals. Three instantaneous values of the input sinusoidal signal and three instantaneous values of the additional sinusoidal signal are measured sequentially in time at a fixed reference time interval, and the third instantaneous value of the input sinusoidal signal is measured simultaneously with the measurement of the first instantaneous value of the additional sinusoidal signal.

one

4i

The frequency of the signal is determined according to a mathematical expression.

f 1 UdJ - IhUi ...

f vri arccos zopn W (1)

where A is the value of the reference time interval;

Ui.Ut.,

U3 and U,

Hi, Uj are the instantaneous values of the input and additional sinusoidal signals, respectively.

The validity of the mathematical expression (1) can be proved as follows.

Let V., V. amplitudes of mutually orthogonal sinusoidal signals, then the measurement results of their instantaneous values are expressed as

L, V cos (at - 2 (OL),

 VAcosfa) t - (04),

U3 VA cosLO t,

Uj vrsin (jt,

Ui VR sin (CDt + W),

 VRsin (Wt + 2 “A).

Express the expression

-a-Ј- -а cos (at -Ш) sin () - VAVR

-cosLOt.sinQt 5 (sin2QU + sin2CQt) - sin2 (i3t - sin2U) A.

Using additional samples U, and 1) 3, remote from U} by 2OD, you can get

1, l, -

 sinACOA -

 AVR last two expressions

s1p4 (yd

8ln2cou -

from where

cos2G3A

U, U3 - yvL l

2 (U2UJ U, U,) and at f (0 / 21Г

1U4U3 - IHU

f arccos H7G-GCP GT

A IIU 2 (b2U - Ugtf)

Thus, the result of determining the frequency does not depend in principle

five

0

0

40

five

thirty

35

45

50

55

from amplitudes of mutually orthogonal sinusoidal signals, the ratio between which can be arbitrary, which is an advantage of the method over the known

The drawing shows a block diagram of the device that implements the proposed method.

The device contains an analog-to-digital converter 1, a generator

2-stroke pulses, digital filters 3 and 4 of the first and second types, registers 5-10 packets, blocks 11-13 multiplication, blocks 14-15 subtraction, block 16 divisions, digital-to-analog converter 17 and functional converter 18.

The output of generator 2 is connected to the control inputs of digital filters.

3 and 4 and analog-to-digital converter I, the output of which is combined with the inputs of digital filters 3 and 4. The output of digital filter 3 is connected through serially connected memory registers 5-7, and multiplication unit 13 is connected to the combined first inputs of subtractors 14 and 15, and the output of digital filter 4 is connected via serially connected memory registers 8-10 and multiplication unit 11 is connected to the second input of subtraction unit 14. The outputs of memory registers 5 and 8 are connected respectively to the second inputs of multiplication blocks 11 and 13. The outputs of memory registers 6 and 9 are connected to the inputs of the block

12 multiplication, the output of which is connected to the second input of the subtraction unit 15. The outputs of blocks 14 and 15 of the subtraction are connected to the inputs of block 16, the output of which is connected through a series-connected digital-to-analog converter 17 and a functional converter 18 to the output of the device.

The device works as follows

The monitored voltage is fed to the analog input of the analog-digital converter 1, which, together with the 2 clock pulse generator, converts the instantaneous values of the monitored voltage to a digital code. This code goes to the combined inputs of digital filters 3 and 4, which, together with the generator 2, perform digital filtering, reducing the effect of higher harmonics.

AND

of At the same time, at the outputs of digital filters 3 and 4, there are sequences of codes in –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––

In a group of serially connected memory registers, information about three consecutive instantaneous values of the cosmic and numerical components of the input signal U is scaled, and the second group of memory registers contains information about three consecutive instantaneous values of the sinusoidal components of the input signal U. With this value of cosine-sonals of the Oh component, Uj, G, L j, the shift of У in time (by 2D OTHoiiiennK) to the sinusoidal components U |, Г ,,, lj, respectively.

The multiplication unit I1 multiplies in a digital trial the signals of the first instantaneous cosinusoidal component G (and the third instantaneous value of the sinusoidal component Uj of the controlled voltage. In multiplication unit 12, the operation of multiplying the second instantaneous values of the cosine LL and sinusoidal LЈ composition is performed, multiplying the second instantaneous values of the cosine LL and sinusoidal L composition and the multiplication of the second instantaneous values of the cosine LL and the sinusoidal LЈ composition In multiplication unit 13, the operation is performed by multiplying the third instantaneous value of the cosine-shaped component U and the first instantaneous value the constricted component UJ of the monitored voltage. The unit 14 performs the subtraction from the result at the output of the multiplication unit 11 at the output of the multiplication unit 13. The unit 15 subtracts from the result at the output of the unit 12 the output at unit 13. In the unit 16 dividing the result at the output of the subtraction unit 14 by the doubled result at the output of the subtracting unit 15.

46

chifro l tax reopra chots.tm l. 1 7,

WHICH PREP RACH G Illhi j CODE &

analog cnrnai. Pokh-kdpin is processed by the function fi-cell ii lii-iri n1im1) p, | chova - gel 18 (nrcros).

So OPF f, iniie orthogonal signals and their processing and compliance with the rni icci mate and h expression (1) 1SChWOL (T 1yut1 SP I) ACCURACY

determination of the frequency of a sinusoidal signal frequently, MeiiLiiict / pi ge. ti of its half-period, forms of a l a and h o (1 p with these and

The method of determining the frequency of a sinusoidal) smignall, based on the successive in time of the measurement of two MULTIFUNCTION values of the input sinusoidal spgppts and two instantaneous values of the generated additional sinusopal long-range signal, taken in both cases at a reference time interval of about a liter and with the fact that, for the purpose of newer accuracy, the additional sinusoidal signal is formed orthogonal with respect to the input sinusoidal signal and, additionally, the third instantaneous values of the input signal About an additional signal. 1.x signals that, e through a reference time interval, and ... the measurement time of its instantaneous value of the input sinusoidal signal coincides with the measurement of the first instantaneous value of the additional sinusoidal signal, and the frequency f is determined according to a mathematical expression

f arccos

uLu2 - and, y,

2 ()

the value of the reference time interval;

instantaneous values, respectively, of the input and additional sinusoidal signals.

II

Claims (2)

A method for determining the frequency of a sinusoidal signal, based on a sequential measurement of two instantaneous values of the input sinusoidal signal and two instantaneous values of the generated additional sinusoidal signal, taken in both cases through a reference time interval, and so on and so on. that, in order to increase accuracy, an additional sinusoidal !! the signal is formed orthogonal with respect to the input sinusoidal signal and additionally measure the third instantaneous values of the input and additional sinusoidal signals also through the reference time interval, moreover, the moment of measurement of the third instantaneous value of the input sinusoidal signal coincides with the measurement of the first instantaneous value of the additional sinusoidal signal, and the frequency f is determined according to mathematical expression 1 and, and, - υ, υί ^f 4 ^ ^arccos 2 (ΰ _? _Ϋ [~ υ ₃ ΰ [) where D are the values of the reference time interval; U ₄ , C _g , Uj and And ₍ ,, U1 - instantaneous values respectively 2 of the input and auxiliary sinusoidal signals.