SU1265651A1 - Device for giving signals with calibrated values of amplitude modulation factor - Google Patents

Abstract

The invention relates to a pulse technique and can be used to test modlometers and to create standards for the amplitude coefficient J4pdilyat. The purpose of the invention is to increase accuracy. The device includes a reference generator 1, voltage dividers 4, 5, adder 6, feedback circuit 9 formed by phase detectors 10, 11 and 12 and controlled by reference generator 13, switch 14 and signal level meter 15. Performing the signal sources 2, 3, and 7 of the upper sideband, carrier frequency, and lower sideband, respectively, in the form of frequency synthesizers, allows obtaining precise values of the amplitude modulation factor of signals with a small distortion of the bending curve. The error of the set value of the amplitude modulation factor is determined by the error of the signal level meter and does not exceed S 0.1-0.5% at frequencies up to 100 MHz. 1 il. /four

Description

The invention relates to measurement technology and can be used to test modlometers and to create standards of amplitude modulation (AM). The purpose of the invention is to improve accuracy by obtaining precision values of amplitude modulation coefficient of signals with small envelope distortions.

The drawing shows a structural electrical circuit of the proposed device.

The device for generating signals with calibrated values of the amplitude modulation coefficient contains a reference generator 1, a source 2 signals of the upper sideband, a source 3 of carrier frequency signals, voltage dividers 4 and 5, an adder 6, a source 7 of signals of the lower sideband, divider 8 voltage feedback circuit 9, formed by phase detectors 10-12 and controlled by a reference generator 13, a switch 14 and a meter 15 levels of signals. Sources 2, 3 and 7 signals are made in the form of frequency synthesizers. The output of the reference generator 1 is connected to the inputs of sources 2 and 3 s. The voltage outputs, through which the voltage divider 4 and 5 are connected respectively to the inputs of the adder 6, the signal source 7 is connected to the auxiliary input through a voltage divider 8, the outputs of the signal sources 2 and 7 are connected respectively to the first inputs of the phase detectors 10 and 11, the second the inputs of which are interconnected and with the output of the signal source 7, in I the voltages of the dividers 4, 5 and 8 under the voltage, are connected via a switch 14 to the input of the meter 15 levels.

The operation of the device is based on the principle of linear summing of the powers of the three associated signal sources and thus the formation of the AM signal.

The sources of the carrier frequency signals 3 of the upper sideband 2 and the lower sideband 7 produce sinusoidal voltages with frequencies.

(one)

carried (2)

f carried

(3)

- F,

m

carried

where f

fr signal frequencies

and

g sources 2, 3 and 7, respectively;

carrier value

- carried frequencies;

FM modulation frequency value.

The required level of each spectral component, Chz., U, Ug, is set independently using voltage components 4, 5 and 8 on the meter 15 signal levels.

Thus, at the output of the linear adder 6, the voltage of the amplitude-modulated signal with a fixed frequency F is formed.

L

and the AM coefficient, the installation error of which is determined mainly by the accuracy of the meter 15 levels.

The envelope distortion of the AM signal depends mainly on the level of the plots of the component signals U4, Uj, Ug.

To automatically fulfill the conditions (2) and (3), the sources of the signals of the upper sideband 2 and carrier frequency 3 are synchronized by the reference generator 1.

In addition, the output voltage

signal sources are compared at phase detectors 10 and 11 and the resulting beat signals are then compared at phase detector 12.

The error signal from the output of the phase detector 12, acting on the controlled reference oscillator 13, synchronizes the frequency of the source 7 of the signals of the lower sideband.

In the known envelope distortion device, the phase-frequency characteristics of the channels are not identical and the phase fluctuations in the PLL provide for maintaining the phase characteristics of the summed signals.

Claims (1)

In the proposed device, phase 0 fluctuations (deviations from instantaneous phase equality) of the summed signals are reduced by 2-3 orders of magnitude with the help of a feedback circuit. The AM signal envelope distortion does not exceed 0.01-0.05% for any AM coefficients. At the same time, the accuracy of the set value of the AM coefficient is determined by the error of the signal level meter and does not exceed 0.1-0.5% at frequencies up to 100 MG. three signal sources, the outputs of which are connected through voltage dividers to the inputs of the adder, a voltage level meter connected via a switch to the inputs of the adder, as well as a controlled reference generator and phase detectors In order to increase accuracy by obtaining 514 precision values of the amplitude modulation factor with low envelope distortion, the signal sources are made as frequency synthesizers, the outputs of the first and third signal sources being connected to the first inputs of the first and the second phase detectors, the second inputs of which are combined and connected to the output of the second signal source, the outputs of the first and second phase detectors are connected to the inputs of the third phase detector, the output of which is connected n to the input of the controllable reference oscillator, whose output is connected to the input of a third source signal inputs of first and second signal sources are connected to the reference oscillator output.