SU1187093A2 - Comparator of closely spaced frequencies - Google Patents

Abstract

COMPARATOR CLOSE FREQUENCIES on auth. No. 413431, characterized in that, in order to improve accuracy, an additional frequency divider is introduced in it, the output of which is connected to the auxiliary input of the third mixer, and the input is connected to the output of the frequency multiplier of one of the channels.

Description

The invention relates to frequency measurements and is intended for comparing stable frequency sources with great accuracy and is an improvement of the known device according to the author. No. 413431.

The aim of the invention is to improve the frequency comparison accuracy by reducing the error due to phase fluctuations of the local oscillator signal.

The drawing shows a block diagram of the proposed device.

The near frequency comparator contains in the measured and reference frequency channels mixers 1 and 2 frequencies and multipliers 3 and 4 frequencies, a common local oscillator 5, an additional frequency divider 6, a third mixer, frequencies, a frequency divider 8, a counter 9, a frequency multiplier 10 and a driver 11 pulses

The frequency mixer 1 (2) is connected in series with the frequency multiplier 3 (4). The outputs of the multipliers 3 and 4 frequencies are connected to the inputs of the third mixer 7, the output of which is through the frequency divider 8, connected to the control input of the counting device 9, the counting input of which is connected through the serially connected frequency multiplier 10 to the output of one of the channels Output frequency divider 6 is connected to the auxiliary input of the third mixer, and the input is connected to the output of the frequency multiplier of one of the channels.

The comparator works as follows.

Harmonic signals of the reference t, and the one to be compared (measured). {, (iofii) frequencies are fed to mixers 2 and 1 frequencies. The second inputs of these mixers receive harmonic signals from the local oscillator 5 with the frequency o (where R. (n)). Signals with frequency Gd and () from the outputs of mixers 2 and 1 are fed to multipliers 4 and 3 frequencies with fractional

I multipliers n -t- and

n), 1 g

P n,, gdet ,, n,, Wj and Ig - integers. The signals from the output of multipliers 3 and 4 ofg and P (F, -o, f) are fed to the inputs of the mixer 7 frequency. The signal from the output of the multiplier 3 is fed to a frequency divider 6, having a division factor of p, which can have a fractional value.

The signal from the output of the multiplier 4 is fed to the frequency multiplier 10, having a multiplication factor m,. The signal from the divider 6 frequency P () ti is fed to the third input of the mixer 7

From the output of the mixer 7, the signal with frequency FX equal to the frequency difference of the three input signals is fed to frequency divider 8. In divider 8, the frequency of the signal Fj; is divided by h times in order to obtain ol n / Fjv time intervals equal to the standard (1 s, 10 s, 100 s, etc.). The signal from the output of the divider 8 is fed to the counting device 9, operating in the period measurement mode.

From the output of the multiplier 10, the signal with frequency i (h. Am hp is fed to the pulse shaper 11 and then to the counting device 9. In this case, the reading N of the counter depends on the difference i of the input matching frequencies. This dependence is established from the following relations

p.-IK-pi-p /.

where in brackets is +, if p and vice versa, in front of the bracket is +, if vice versa. Cases substitution p fri, / and; o "m, j / fz and entering new notation

| t, Pg-tgP, (L- (Vn, 10) / m n -linj / k;

/ we have

kFn + mnibl

fy lna-fo 4

Single measurement time

-. -. . kFQ-vwn4b

The frequency of the counting pulses ICM H RO

PP4

...; 7 ;;;;; iIfree iO (in self-control mode) when the signal of the same frequency „() | ppp4 arrives at both inputs of the comparator of close frequencies. . N NO- -JJ - const. When o (in measurement mode), when the comparator receives the reference to and the measured frequency i (mnn4fo oe J. From where Kl-J a. I-i x-2: o, t. 0 0 xo / "4o. that AN 1, v we obtain the value of the calculated resolution ... mn4N ° mn Cx where Tc is the period of the following counts of impulses of its nominal value. Therefore, the true value of fg is taken to be the value of PO (n oV const, (where bn is the nominal value the frequency of hetero 3 is different) and the calculation is made by the expression K ir "- The error caused by fluctuations of the local oscillator 8 (ui) is equal to where Kip is the fluctuation of the frequency of the local oscillator. The choice of the coefficients t, t, F produced with the calculation of obtaining a given resolution (price per unit of account) and minimum values of the coefficients h and k. In particular cases, the coefficients and, simultaneously or separately, can take single values. In the proposed comparator scheme, the error due to the frequency (or phase) fluctuations of the local oscillator is suppressed by Mh / k times stronger. Therefore, practically adjusting the frequency of the generator is not required even if it is significantly deviated from the n L1 value. The essence of the proposed comparator does not change if the input of the frequency divider 6 is connected to the output of multiplier 4. The frequency mixer 7 to the three inputs can be implemented on any non-linear element with three inputs with selective output circuits.

Claims (1)

COMPARATOR OF CLOSE FREQUENCIES according to ed. No. 413431, characterized in that, in order to improve accuracy, an additional frequency divider is introduced into it, the output of which is connected to the additional input of the third mixer, and the input is connected to the output of the frequency multiplier of one of the channels.