RU1800625C - Device for checking amplitude-frequency characteristics of four-thermal networks - Google Patents

Abstract

Usage: for automatic control of the frequency response of four-terminal devices. SUMMARY OF THE INVENTION: the device comprises a control unit 1, a lowpass filter 2, two equalizers 3 and 8, an amplifier 4, a controlled attenuation store 5, a switch 7, a level meter 9, an indication unit 6, a sawtooth generator 10. 1-2-3-4-5-11.5-7, 11-7-8-9-1, 1-10, 1-6, 1-9, 10-5, 1-7. The reduction of the monitoring time is achieved by simultaneously supplying the entire necessary spectrum of frequencies to the input of the four-terminal under study. 1 ill.

Description

The invention relates to radio measurement technology and can be used to automatically control the amplitude-frequency characteristics (AFC) of four-terminal devices.

The purpose of the invention is to reduce control time.

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

A device for monitoring the amplitude-frequency characteristics of the four-terminal network contains a control unit 1, a low-pass filter 2, a first corrector 3, an amplifier 2, a controlled attenuation store 5, an indication unit 6, a switch 7, a second corrector 8, a level meter 9, a sawtooth generator 10 In addition, the studied quadripole 11 is also shown.

The device operates as follows.

The control unit 1 sets the minimum attenuation coefficient of the controlled attenuation store 5 by forming a rectangular pulse at one of its terminals. This pulse is supplied to the input of a sawtooth voltage generator 10, at the output of which a constant voltage of a certain level equal to the first stage is set. This voltage is supplied to the input of the control attenuation store 5, which is a controlled voltage divider made on the basis of a field effect transistor as a controlled resistance.

After that, the control unit 1, which is a computer (microcomputer), begins to generate at one of its outputs a sequence of rectangular pulses with a duty cycle q 2:

 -Ј- ° where Ti is the duration of one period of the impulses;

ti - pulse duration.

The spectrum of this sequence has only odd components. When decomposing it in the Fourier series, we have

Un

00

2 Um

k 1 klg

+ 2

sin

7G

2

coskQ; t

and

m, 2 Um

7G

{COS Qc t - COS 3 Q; t +

- COS 5 Qc t - -y COS 7 Qc t + ...},

5

0

5 0 5

0

5

0

5

where Dm is the amplitude of the rectangular pulse;

Q: is the fundamental frequency of a sequence of rectangular pulses.

Thus, the spectral components contained in the spectrum of a sequence of rectangular pulses are simultaneously input to the input of the four-terminal 11 under study. It is necessary that Ti Јi, where He is the lower monitored frequency, for studying the frequency response of the studied quadrupole 11.

It is easy to see that the amplitudes of the spectral components decrease at a rate of 5 dB / octave.

The low-pass filter 2 is designed to pass the spectral components in the passband of the studied quadripole 11 (for example, for the speech range of the radio communication system, the lower frequency - the fundamental frequency, will be 300 Hz, and the upper frequency - the 11th harmonic frequency - 3300 Hz) . From the output of filter 2, the signal is fed to the input of the first corrector 3 having an increase in the frequency response of the bdB / octave in the passband of the four-terminal network. At the input of the first corrector 3 there will be a signal having spectral components of the same level. The amplifier 4 and the controlled attenuation store 5 are designed to generate a predetermined signal level at the input of the four-terminal 11 under investigation. Next, the signal is fed to the input of the amplifier 4 having a fixed gain, and then to the controlled attenuation store 5 having a predetermined attenuation coefficient.

From the output of the controlled attenuation store 5, the signal is fed to the input of the studied four-terminal 11 and to the first input of the switch 7. The signal from the output of the studied four-terminal 11 is fed to the second input of the switch 7.

The control unit 1, using a controlled signal, switches the signal from the input of the studied four-port terminal 11 to the output of the studied quadrupole 11. This signal is fed to the input of the second corrector 8, which has a decrease in the frequency response of 6 dB / octave in the passband of the studied four-terminal 11. From the output of the second corrector 8, the signal arrives at the input of the level 9 meter, based on an analog-to-digital converter, where it is converted into a digital code, which the level meter 9 exchanges with the control unit 1.

The control unit 1 stores the received code in the internal random access memory (RAM). After that, the unit 1 commutates, using a controlled signal, to the output of the switch 7, the signal from the output of the studied quadripole 11, prohibiting the passage of the signal from its input, and the signal conversion described above is repeated.

The control unit 1, exchanging a digital code from the level 9 meter, compares the programmatically received signal codes from the input and output of the studied four-terminal 11 and, if their difference does not go beyond the permissible limit, block 1 transmits to the display unit 6 a digital code of the Norm signal, which is initialized on the light panel of the indicating unit 6, if the difference is outside the permissible limit, the signal code Not normal is transmitted.

Thus, the result of monitoring the frequency response of the four-terminal 11 under study is a Norm or Not signal at a given signal level at its output.

After that, the next step in the attenuation coefficient of the controlled attenuation store 5 is established, and the frequency response control cycle of the studied quadrupole 11 is repeated.

There can be several stages (or steps) of attenuation of the transmission coefficient (in practice this amounts to 8-10 steps).

The Normal or Non-normal signals and the stage number are displayed on the light panel of the display unit 6.

The time to control the frequency response of the studied four-terminal 11 will be equal to twice the duration of one period of the sequence of rectangular pulses, i.e.

T 2

1 IE1

where Q; - the frequency of the fundamental harmonic, which is much faster than the control time of known devices, and the frequency response control, based on a comparison of the input signals and

Claims (1)

the output of the four-terminal network allows the amplitude-frequency response to be controlled with a high degree of accuracy. SUMMARY OF THE INVENTION A device for monitoring the amplitude-frequency characteristics of a four-terminal network comprising a control unit, an indication unit, a level meter and a controlled attenuation store, characterized in that, in order to reduce the monitoring time, a low-pass filter is connected in series, the input of which is connected to the first output of the control unit , the first corrector and amplifier, the output of which is connected to the input of the controlled attenuation store, the output of which is the output for connecting the input of the four-terminal under investigation, a sawtooth voltage generator, the input and output of which are connected respectively to the first control output of the control unit and the control input of the controlled attenuation store, connected in series to a switch, the first input of which is input for connecting the studied four-port network, and the second corrector, the output of which is connected to the information input of the level meter, the output of the controlled attenuation store is connected to the second input of the switch, the control input of which is connected to the second control output of the control unit, the information input and output of which are connected respectively to the information output of the meter level and the input of the display unit, the third and fourth control outputs and the control input of the control unit are connected respectively to the first and second control their inputs and a control output of the level meter.