SU1529460A1 - Automatic frequency control device in radio and television receivers - Google Patents

Abstract

The invention relates to radio engineering and communication technology. The purpose of the invention is to reduce the nonlinear distortion coefficient. The device contains a high-frequency block 1, an intermediate frequency block 2, a frequency discriminator 3, an adder 4, a control key 5, a control block 6, a control key 7, potentiometers 8, 9, 10, a switch 11 of fixed settings. The device operates in manual adjustment mode and in the automatic frequency control mode. In the AFC mode, the frequencies are adjusted with a minimum of nonlinear distortion at the output of frequency discriminator 3 due to the shift of the operating point of frequency discriminator 3 as a result of the input of the first reference signal into the AFC loop. 1 il.

Description

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The invention relates to radio engineering and communication technology and can be used in high-quality broadcast radio and television receivers of frequency-modulated signals.

The aim of the invention is to reduce the non-linear distortion factor.

The drawing shows a structural electrical circuit of the device for automatic frequency control in radio and television receivers.

A device for automatic frequency control in radio and television receivers contains a high-frequency block 1, an intermediate frequency block 2, a frequency discriminator 3, an adder 4, a first control key 5, a control block 6, a second control key 7, potentiometers 8-10, a switch II fixed settings.

The device works as follows

In the manual tuning mode in the control unit 6, the anti-phase signals are supplied to the control inputs of the controllable keys 5 and 7, the first control key 5 is open, and the voltage of the second reference signal is applied to the potentiometers 8-10 through the second control key 7 - the tuning tuning, taken from the movable terminals of the potentiometers, through the switch of the fixed settings is fed to the control input of the high-frequency unit 1, which is tuned to a frequency with a minimum of non-linear distortions at the output of the frequency discriminator 3, The voltage at the output of the adder 4, obtained from the voltage at the output of the frequency discriminator 3 and the appropriately selected voltage of the first reference signal, is equal to the voltage of the second reference signal Uoni-mode auto-adjust

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frequency (A11CH) second controlled key 7 is open, and through the first controlled key 5 to the potentiometers 8-10 supplied voltage from the output of adder 4, equal to the voltage of the second reference signal, Thus, in the frequency control mode provides a minimum frequency adjustment nonlinear distortion at the output of the frequency discriminator 3 due to the shift of the operating point of the frequency discriminator 3 as a result of the input of the first reference signal into the AFC loop.

Claims (1)

Invention Formula A device for automatically adjusting the frequency in radio and television receivers, containing a series-connected high-frequency unit, an intermediate frequency unit and a frequency discriminator, the adder, the first input of which is the input for connecting a reference signal, a control key, a control unit, potentiometers connected in parallel, one terminal which are connected to the common bus, the fixed settings switch, the control input is controlled to the control unit, the control unit is connected to the output of the control unit, the moving outputs are sweat The meters are connected to the corresponding inputs of the fixed settings switch, the output of which is connected to the control input of the high-frequency unit, characterized in that, in order to reduce the nonlinear distortion coefficient, a second control key is entered into it, the input of which is the input for connecting the second the reference signal, the control input is connected to the anti-phase output of the control unit, the outputs of the first and second control keys are connected to other terminals of the potentiometers, and the adder is connected between the output astotnogo discriminator and the input of the first key.