SU559455A1 - Device for measuring the signal-to-noise ratio in a television signal - Google Patents

Description

A selector, the first input of the time selector is connected to the output of the switch, the second input of which is connected to the output of the level fixing unit, the second input of the time selector is connected to the third output of the unit and fixing, selection and gating, the output of the time selector to the input of the low-pass filter , and the output of the display unit is connected to the third input of the switch.

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

The device contains a series-connected switch /, time selector 2, low-pass filter 3, gating and memory unit 4, first variable voltage to constant voltage converter 5, computing unit 6, analog-to-digital converter 7 and display unit 8. Output of the second converter 9 AC voltage is connected to the second input of the computing unit 6, its first input is connected to the input of the 10 pulses fixation, selection and gating unit, the first input of the // // fixation unit and the switch input /, the second input of which is connected to the output of the block} / fixation unit; n, and the third input - with the output of the indication unit 8. The first output of the block 10 fixing, selection and gating pulses is connected to the second input of the fixing unit 11 and to the second the input of the second transducer 9. The second output of the block 10 of fixation, selection and gating pulses is connected to the control input of the gating unit 4 and memory, and its third output is connected to the second input of the time selector 2.

The device works as follows.

The input is a full television signal (PTWS), struck by a frequency multiplier disturbance. This signal simultaneously arrives at the first input of the collator 1, to the input of the block 10 of latching pulses, selection and gating and to the transducer 9, where the amplitude of the image signal is converted to a voltage with an open input and the latching level of the pulses. to the zero potential of the pulse М1И fixation, coming from the block 10 of the pulses of fixation, selection and gating.

From the // fixation unit, it is fixed at the back pads of the lowercase extinguishing pulses of the NTVS and arrives at the second input of the switch /.

With the help of the control signal from the iDik 1; i 8 and switch / switchboard, the measurement mode of the additive noise is selected (without a level fixing indicator) 1Imultiple interference noise (with level fixing). From the output “ohm: attenuator 1 PTVS comes the input of the low-pass filter 5, serving to reduce the error due to the presence of high-frequency fluctuation interference in the PTVS. From the output of the low-pass filter 5, the signal arrives and the input of block 4 is gated1-; and memory, the control of the KOTOiporo input receives pulses of C-robiro.vai from the unit of 10 pulses of selection, selection and gating. These pulses are done by gating the image signal and storing its level.

to the ir of the same line in the next frame and the next gating imiuls. Thus, a voltage appears in the output of the gating and memory block 4, the shape of which repeats the shape of the low-frequency noise envelope at the output of the switch 1 with a sweep equal to that of O1, and where / «is the frame rate and In is the frequency of low-frequency interference.

This voltage from the output of block 4 and memory is fed to the input of converter 5, from the output of which the range of low-frequency interference in the form of a constant input is fed to the first input of the block of power supply 6, to the other input of which constant voltage is Images from converter output 9.

Computing unit 6 calculates the ratio of input voltages, and the result, in the form of a constant voltage proportional to the ratio of the image signal to low frequency interference, from its output enters the analog-digital input

converter 7. From the output of analog-to-digital converter 7, the result of the conversion in the form of a digital code is fed to the input of a search unit 8, which switches the switch / after a certain time

for measuring the multiplex | Ikativia and additive components of the low-frequency disturbance and provides an indication of the measured values.

The application of the invention makes it possible to measure with high accuracy the amount of low-frequency interference that gets into the television signal before the introduction of damped and synchronized pulses into it.

Claims (2)

1. USSR author's certificate No. 217439, M. Kl2. H 04 N 5/16, 1972. 2. USSR author's certificate L 313315, M, Cl. 2 H 04 N 7/02, 1974.