SU1584072A1 - Close frequency comparator - Google Patents

Abstract

The invention relates to an electrical measuring device and can be used to compare the frequencies of highly stable generators with high accuracy. The purpose of the invention is to improve the measurement accuracy while reducing the requirements for node accuracy. The device contains frequency dividers of 1–5, mixers 6, 7, frequency multipliers 8, 9, shaper 10 counting pulses, counting unit 11. In self-control mode, a reference frequency signal is supplied to both input buses 12, 13, counting number 11 is obtained in counting unit 11 0. Then, a controlled frequency is supplied to bus 12, the number N X is obtained in counting unit 11. The input frequency difference ΔF is determined based on the difference ΔN = NX - N 0. The use of dividers 2-5 with fractional frequency division coefficients satisfying certain conditions m, allows to reduce the requirements for fi at the outputs of the mixers. 1 il.

Description

The invention relates to electrical radio engineering and is intended to compare with high accuracy the frequencies of highly stable frequency sources and measure their relative instability. 5

The purpose of the invention is to increase the accuracy of measurements while reducing the requirements for the accuracy of tuning nodes. > 10

The drawing shows a structural diagram of a comparator.

The comparator contains from the first to the fifth frequency dividers 1 to 5, the first 6 and second 7 mixers, the first 8 and second 9 15 frequency multipliers, the counting pulse generator 10, the counting unit 11, the signal of the controlled frequency, the signal bus of the reference frequency, the output bus 14 . 20

Bus 12 through the fourth divider 4 is connected to the first input of the first mixer 6, the second and third inputs of which are connected to the outputs of the second 2 and fifth 5 dividers respectively, the inputs of the last 25 are connected to bus 13, the input of the third divider 3 and, through the second multiplier 9 and the shaper 10 - with the counting input of the counting unit 11, the output of which is connected to the output bus 14. The output of the first mixer 6 through the first multiplier 8, the second mixer 7, the first divider 1 is connected to the input of the counting unit 11. The second input of the second mixer 7 is connected to exit third divider 3. 35

The first divider 1 has a frequency division coefficient u. The second, third, fourth and fifth dividers 2-5 have fractional frequency division factors pg / tg, pz / tz, pd / tf P5 / t5, respectively. The first 8 and second 9 multipliers have frequency multiplication factors Ks. Ke respectively.

The comparator works as follows: 45

The harmonic signals of the reference fo and the compared f _x ~ fo + Δί frequencies are fed to the divisors 2 and 4 with fractional division coefficients' pg / tg and gm / ggm, respectively. The reference frequency signal also arrives at 50 frequency dividers 3 and 5 with fractional division coefficients, respectively pz / tz and pb / gpy, to multiplier 9 and shaper 10 connected in series.

First, for simplicity, it is assumed that 55 Δί = 0 (f _x = fo) · The output signals from dividers 2, 4, and 5 are fed to a mixer, the output of which is a signal with a frequency Fi:.

| ~. Ι | 1 i 'W ·' Z | * ¹ I ¹ ~ I 04 n £ I П5 I ^Т ° '

The coefficients gp4, tg, P4, pg are selected based on the conditions

I ПГ14 П2 - Γ П2 П4 | = 1 And | GT14 - P4 I = ’= ΓΐΊΊ2 *“ P2 | ~ 1.

In this case

F, = I -J - SS

I 0402 05 fo

The coefficients of the GTZ and ns are selected based on the condition | Pe - 04 02 gl5 | = 1.

Then the expression for Fi takes the form

Fi =

P2 05

The frequency signal Fi is supplied to a multiplier 8 having a multiplication factor Kv (it is advisable to take the Kv value in the range from 10 to 20). From the output of the multiplier 8, a signal with a frequency of Ke Fi is fed to a mixer 7, to the second input of which a signal with a frequency of ts / pz · fo from a divider 3 is fed. At the output of a mixer 7, a signal with a frequency of

Fo =

Sq

P4P2P5

The coefficients tk and pz are selected based on the condition

I Kvpz - GPZP4P2P5 j = 1.

The expression for Fo takes the form ^F ° P4P2P3P5 ^f °

The signal Fo is the output signal of the second mixer 7 in the self-monitoring mode (at Δ f = 0), when the reference frequency signal fo is applied to both inputs of the comparator.

When Δf 0 (in the mode of measuring the frequency F _x signal at the output of the second mixer 7 is

F _x = Fo

GP4

P4

Kv · Δ f = Fo ± m Δ f, (1) where the plus sign will be in the case, ес and Δί does not change sign when passing through the smegels or changes an even number of times, m = td / pd · Ka is the total multiplication coefficient of the difference of the compared frequencies . The signal F _x goes 5 to divider 1, where it is divided by m times to obtain the measurement time intervals Tx = πι / F _x equal to the standard ones (1 s, 10 s, 100 s, etc.).

The signal from the output of the divider 1 enters 10 to the counting unit 11, operating in the period measurement mode. A signal frequency fen = Kg 'fo also arrives at the counting unit 11 from the shaper 10.

The readings of the counting unit 11 depend on the difference of the compared frequencies. This dependence is determined by the expression

Δί = +

P1 Ch. Guo Τχ

Δτ =

I M fc4 m Ν _ο Νχ '(2) where r0 = ni / Fo; rx-ni / Fx Ar = Tx-Go;

No. N _x - readings of the counting unit in the self-monitoring mode (at Af = 0) cooT respectively; ΔΝ = Ν _χ -Νο.

The sign in expression (2) is placed opposite to the sign of the term in expression (1). 35

Using the comparator according to the described scheme allows to reduce the error of measuring the frequency difference and to exclude its dependence on the difference of the compared frequencies. The maximum difference between the compared frequencies is determined by the passband of the filter at the output of the second mixer 7.

Compared with the known frequency comparator, the tuning is significantly simplified, since there is no need for narrow-band quartz filters at the outputs of the mixers. The exclusion of these filters can also reduce the error due to temperature changes. In addition, the proposed frequency comparator uses a frequency multiplier with a lower multiplication coefficient than the known one, which reduces the level of spurious fluctuations that occur in the comparator.

Claims (1)

Claim A close frequency comparator comprising a first mixer, a first frequency multiplier, a second mixer, a first frequency divider and a counting unit, a second frequency multiplier and a counting pulse shaper connected in series, the output of which is connected to the counting input of the counting unit, as well as a second and third frequency divider moreover, the input of the third frequency divider is connected to the bus signal of the reference frequency and the input of the second frequency multiplier, and the output to the second input of the second mixer, characterized in that, in order to increase the accuracy of comparison while reducing the requirements for the accuracy of tuning the nodes, the fourth and fifth frequency dividers are introduced into it, the input of the fourth frequency divider connected to the signal bus of the controlled frequency, the output to the first input of the first mixer, the second input of which is connected to the output of the second a frequency divider, the input of which is connected to the bus signal of the reference frequency and the input of the fifth frequency divider, the output of which is connected to the third input of the first frequency mixer, while the second, third, four the fifth and fifth frequency dividers are made with a fractional division coefficient pg / tg, pz / tz, pd / td, p5 / gp5, respectively, where p2, pz, pd, p5, m2, tz, td, ms are integers satisfying the conditions j GPDP2 - GP2PD | = 1; | G> 5 - PDP2GP5 | = 1; | Kapz - GPZPDP2P5 | = 1, where Ka is the frequency multiplier of the first frequency multiplier.