SU534886A1 - Device for measuring the signal-to-noise ratio in television systems - Google Patents

Description

one

The invention relates to television technology, and specifically to devices for measuring the signal-to-noise ratio in television systems. It can be used in applied television systems and in television radiation introscopy

A device for measuring the signal-to-noise ratio in television systems is known, comprising a serially connected video amplifier, a latching circuit, an emitter follower, the output of the video amplifier being connected simultaneously with the control input of the latching circuit and the inputs of two window signal generators, the circuit for measuring the noise voltage and display unit.

A disadvantage of the known device is the low measurement accuracy at small values of the signal-to-noise ratio.

The purpose of the invention is to increase the measurement accuracy.

For this, the emitter follower output is connected to the signal inputs of two entered autocompensation voltmeters, the control inputs of which are connected

to the outputs of the corresponding generators of the cis inlet window. The high-frequency outputs of the autocompensation voltmeters are connected to the inputs of the pgum voltage measuring circuit, and the low-frequency outputs are connected to the inputs of the entered subtracting circuit. The output of the latter is connected to one of the inputs of the display unit, to the other input of which the output of the noise voltage measurement circuit is connected.

The drawing shows a block diagram of the proposed device for measuring the signal-to-noise ratio in television systems.

Claims (1)

The device contains serially connected video amplifier 1, latching circuit 2, emitter follower 3. The output of the video amplifier is connected to the input of the clock circuit 4, whose outputs are connected to the control input of the latching circuit 2 and the inputs of two signal generators window 5 and 6. The output of the SIMHTTER follower 3 is connected with signal inputs of two entered autocompensation voltmeters 7 and 8, the control inputs of which are connected to the outputs of the corresponding window signal generators and 6. High-frequency auto-output outputs The sensing voltmeters 7 and 8 are connected to the inputs of the noise voltage measurement circuit 9, and the low-frequency outputs are connected to the inputs of the entered subtractor circuit 1O. The output of the circuit 1O is connected to one of the inputs of the display unit 11, the other input of which is connected to the output of the noise voltage measurement circuit 9. The device for measuring the signal-to-noise ratio in television systems works as follows. The video signal is fed to the input of the video amplifier 1. From the output of the video amplifier through fixing circuit 2, the video signal is fed to the emitter follower 3. From the other output of the video amplifier, a signal is fed to the selection circuit of the sync pulses 4. To the input signals of the sync pulse 2 are fed to the control input of the fixing circuit 2 and to the inputs of the sync pulse 2. window 5 and 6, which form a series of rectangular pulses corresponding to the two compared image areas. From the output of the emitter follower 3, the video signal is fed to the signal inputs of two autocompensation voltmeters 7 and 8, which are normally locked. When applied to the control inputs of voltmeters 7 and 8 pulses from the signal generators, window 5 and 6, the voltmeters are unlocked, and the compensating (low-frequency) voltage at their outputs is set equal to the average value of the video signal voltage at the time of the window pulses. So, as both slashes are installed on uniformly updated sections of the image, any instantaneous deviations of the video signal from the average value inside these areas are determined only by noise, therefore, the difference between the video signal and the compensating voltage in each self-compensating voltmeter is equal to the value of the noise voltage . The compensating voltage from the low-frequency outputs of the auto-compensation voltmeters 7 and 8 is applied to the two inputs of the 1O subtractor circuit. From the output of the subtraction circuit 10, the differential voltage is applied to one of the inputs of the display unit 11, to another input of which a high-frequency voltage is supplied from the output of the noise voltage measurement circuit 9. The readings of the display unit 11 are proportional to the ratio of the voltages applied to its inputs, and therefore are proportional to the ratio of the difference between the average values of the video signal corresponding to the two compared image areas to the effective noise value, i.e. signal ratio to the effective noise value. Apparatus of the Invention A device for measuring the signal-to-noise ratio in television systems, comprising a serially connected video amplifier, a latching circuit, an emitter follower, a video amplifier's output simultaneously through a clock circuit connected to a control input of a latching circuit and the inputs of two window signal generators, a noise measurement circuit and a display unit, characterized in that, in order to improve the measurement accuracy, the emitter follower output is connected to the signal inputs of two i.v. The autocompensation voltmeters, whose control inputs are connected to the outputs of the corresponding window generators, have high frequency outputs of the autocompensation voltmeters connected to the inputs of the noise voltage measurement circuit, and the low frequency outputs are connected to the inputs of the entered subtraction circuit, the output of which is connected to one of the inputs of the display unit, and The output of the noise voltage measurement circuit is connected to another input.