SU661387A1 - Frequency small deviation measuring device - Google Patents

Description

(54) DEVICE FOR MEASURING MALB1X FREQUENCY DEVIATION

The invention relates to the field of measurement technology, in particular, to devices for measuring small frequency deviations, and can be used to study small changes in any physical quantity that, when applied to a frequency converter, cause a small change in the frequency of its output signal.

A device for measuring small frequency deviations is known, which is performed by performing forced synchronization of the differential phase-generator measuring transducer 1.

The disadvantage of this device is the non-linear relationship between the magnitude of the phase shift and the frequency offset. In practice, sufficient measurement accuracy is possible only in a narrow range.

Another device is known that contains an input source, a reference oscillator, a phase detector, an indicator 2.

The disadvantage of this device is the non-linear relationship between the magnitude of the phase shift and the frequency offset.

The purpose of the invention is to improve the accuracy of measurement of frequency deviations.

The goal is achieved by the fact that a reference oscillator, the output of which is connected to the first input of the phase detector, the second input of which is connected to the input source, is inserted into the device for measuring small frequency deviations, containing a phase detector, the second input of which is connected to the input source. a controlled attenuator, the control input of which is connected via a functional converter to the output of the phase detector, another input of the controlled attenuator is connected to the output of the source input signal, and the output of the controlled attenuator is connected to the clock input of the reference oscillator.

FIG. 1 shows a functional diagram of the device; in fig. 2 shows the curves of phase and coupling coefficient versus frequency (magnitude of frequency deviation).

The device for measuring small frequency deviations consists of a reference generator 1, a phase detector 2, a functional converter 3, a controlled attenuator 4, an indicator 5, an input signal source 6.

The device works as follows. The reference oscillator 1 is synchronized by an external signal of frequency f (x) through a controlled attenuator 4. When the frequency of the input source 6 is changed between the input signal and the voltage of the reference oscillator 1, the phase shift changes.

The relationship between the detuning in frequency and phase shift within the capture band has the form (Fig. 2a)

where) - detuning in frequency; t is the contour constant; f is the degree of communication; or

Lo t

 - O / tCiun

To obtain a linear transform

), (3)

where K is the conversion factor, from (2) and (3) it is possible to obtain the dependence of the degree of connection (Fig. 2c)

Awl

()

/ 7

 (KAti)}

If the value of connection of the output signal with the reference generator 1 according to the law (4) is changed when changing the value of ш, then the dependence

F (Dso)

will be linear throughout the capture band of the reference generator I (Fig. 2c).

The voltage output from the phase detector 2, proportional to the magnitude of the phase shift, affects the functional transducer 3, which adjusts the degree of coupling of the reference oscillator 1 with the input signal in accordance with expression (4), by acting on the attenuator 4 on a. the amplitude of the clock signal and corrects the nonlinear dependence.

The magnitude of the phase shift is noted on the indicator 5.

The device provides a linear dependence of the phase on the frequency deviation throughout the synchronization band, which increases the accuracy of the measurement of the frequency deviation.

Claims (2)

1. USSR Author's Certificate No. 459739, G 01 R 23/00, 01/26/73. 2. USSR author's certificate number 410242, cl. G 01 B 7/02, 04.01.72. + th ( W 2 aa w + yS -ySh + uU) Well 2