SU107855A1 - Device for selecting video pulses by duration - Google Patents

Description

Devices for selecting video pulses in duration in which the selection is made by combining in time using the delay line of the differentiation products of the leading and trailing edges of the limited pulse and supplying them to the matching stage are known.

In such selectors, selection accuracy depends on the sigpal amplitude, which is their main drawback.

For elimination of this drawback, in the described device, a double differentiation of the signal on linear circuits and a limitation on the zero level of the second derivative of the envelope are applied.

FIG. 1 shows the curves of the pulse of a Gaussian form and its two derivatives. Here: / is the released impulse, 2 is the first and 5 are its second derivatives, B is the pulse amplitude value, g is the pulse duration at the level of 0.786 V and g; -time

Since the pulse of the second derivative is limited to a maximum at a level close to zero, its preamplification is

for any accuracy in determining the duration of a - a, it is not difficult. The only condition for this is the absence of non-linear distortion during preamplification.

Indeed, the impulse of the bell shape is approximated by

F (t) in e

his second derivative

P (O - e

g;

(I-.

where t is the pulse duration at 0.786V.

By limiting the pulse F (t) to the top at a certain level B, a new pulse of approximately rectangular (trapezoidal) shape can be obtained, the duration of which is rigidly associated with the duration of the initial pulse at 0.6 V and does not depend on the amplitude of the latter within any limits given accuracy.

FIG. 2 shows the skeletal diagram of the described device. After twice differentiating the signal on the linear circuits and limiting the pulse to the second derivative of the envelope at a level close to zero, the trapezoidal pulse is amplified, limited to improve its shape and differentiated. The products of differentiation of the leading and trailing edges of this pulse arrive at a separator, after which the product of differentiation of the leading edge is fed to a cascade of coincidence through the delay line, and the product of differentiation of the trailing edge enters the same cascade of coincidence, but without delay. If the duration of the pulse being selected coincides with the line delay time, the products of differentiation of the leading and trailing edges of the pulse arrive at the input of the coincidence circuit at the same time and at its output a starting pulse that triggers the output blocking generator.

Thus, selection is made according to the duration of the initial pulse of practically any shape.

The described device can be used to improve the noise immunity of the receive paths of impulse systems.

Subject invention

A device for selecting video pulses by duration by combining in time using a delay line of differentiation products of the front and rear edges of a limited pulse and feeding them to a matching stage, characterized in that, in order to attenuate the effect of the amplitude change on the selection accuracy, a double signal differentiation is applied on linear contours and the limitation at the zero level of the pulse of the second derivative of the envelope.

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Amplifier

Limiter

Separator

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Match scheme

Output Bloning Generator.

Lineage