JPS62152288A - Burst gate pulse generator - Google Patents

Abstract

PURPOSE:To obtain a burst gate pulse constantly without relating to the size of an input signal by outputting the gate pulse from a burst signal when an input signal level is large and outputting it from a monostable multivibrator when the level is small. CONSTITUTION:When the level of the input chroma signal is large, the pulse formed a comparator 6, namely from the burst signal is used as a burst gate pulse. The level a little larger than the input level in which the burst gate is not outputted at a (g) point is detected by a level comparison means 20, namely in an area which the level of the input chroma signal is lower than this level of a reference DC voltage level of a comparator 4, an analog switch 9 is changed over and the output pulse (c) of the monostable multivibrator 8 having a pulse duration a little longer than burst signal is outputted as the burst gate pulse.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal processing device in a VTR, and more particularly to a device for ordering burst gate pulses for extracting burst signals.

[Conventional technology]

FIG. 2 shows an example of a conventional burst gate pulse generator of this type. In the figure, 11 is an analog switch;
12 is a double-wave rectifier, 13 is a comparator, and 14 is a monostable multivib break.

Further, FIG. 3 shows signal waveforms at various parts of this conventional example.

Next, the operation will be explained.

The input signals are a PAL or NTSC chroma signal a and a synchronization pulse b synchronized therewith. First, the monostable multivibrator 14 is operated using the synchronization pulse as a trigger, and a pulse C having a width slightly wider than the Haas l-signal width of the chroma signal is generated.

Then, with the pulse C, the analog switch 11 extracts the verse 1-a' of the chroma signal a. Then, the burst signal d passing through this analog switch 11 is transferred to a double-wave rectifier 12.
manually to create the burst envelope e. And base 4 of this envelope and the level in the middle! The voltage e' is compared with the voltage e' by a comparator 13, and a burst gate pulse f is generated.

[Problem that the invention seeks to solve]

The drawback of this conventional example is that when the input signal becomes small, the burst gate pulse becomes disordered and is eventually no longer output. Particularly in a VTR, since the burst level fluctuates greatly, such disappearance of the burst gate pulse poses a serious problem.

This invention was made to solve the problems of the conventional ones as described above, and provides a burst gate pulse generator that can output burst gate pulses without disappearing regardless of the magnitude of the input signal. The purpose is to obtain.

[Means for solving problems]

The burst gate pulse generation WW according to the present invention includes a level comparing means for comparing the level of the burst signal extracted from the chroma signal and a reference level, and a first pulse generating means from the pulse generating means in accordance with the comparison result of the level comparing means. and a second switch means for selectively outputting the pulse from the burst gate pulse generating means and the second pulse from the burst gate pulse generating means.

[Effect]

In this invention, the burst signal level is compared with a reference level by the level comparing means, and when the burst signal level becomes lower than the reference voltage level, the output of the pulse generating means is applied to the burst gate instead of the output of the burst gate pulse generating means. Since it is output as a pulse, the burst gate pulse is prevented from disappearing due to a decrease in the input signal level.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure shows a burst gate pulse generator according to an embodiment of the present invention. In the figure, 1 is an input terminal into which the chroma signal a is input, 2 is a first analog switch (switch means) for extracting only the burst signal a' from the chroma signal, and 3 is a circuit for detecting the magnitude of the signal. , a level detector consisting of a synchronous detection circuit and a sample-hold circuit,
4 is a second comparator which outputs a switching signal for the second analog switch when the output DC voltage C of the level detector 3 becomes lower than the reference DC voltage set therein; 21 is a level comparison means; Detector 3. The second comparator 4 compares the output level of the analog switch 2 with the reference level.

Further, 5 is a double-wave rectifier that double-wave rectifies the output burst signal d of the first analog switch 2 and outputs its envelope; a half-wave rectifier can also be used for this. Further, 6 is a first comparator that compares the output f of the double-wave rectifier 5 with a reference voltage set thereto and outputs a burst gate pulse g, and 20 is a burst gate pulse generating means, which is a double-wave rectifier? l vessel 5. It is composed of a first comparator 6 and generates a second pulse, which is a burst gate pulse, from the output of the analog switch 2.

In addition, 7 is an input terminal to which a synchronizing pulse synchronized with the chroma signal applied to input terminal 1 is applied, 8 is 3t, and 1 pulse b is used as a trigger signal to generate a pulse (first pulse) C of a certain constant width. The output monostable multivibrator 9 switches the output pulse of the monostable multivibrator 8 and the output pulse of the second comparator 6 with the output signal of the second comparator 4, and outputs the first gate pulse to the output terminal 10. This is a second analog switch (switch means) for outputting.

FIG. 4 shows the output waveform at each point, and FIG. 5 is a graph showing the switching voltage of the second analog switch that switches the burst gate pulse.

Next, the operation will be explained. When the level of the input chroma signal is high, that is, in the area A in FIG. 5, there is an output pulse from the first comparator, that is, a pulse created from the burst signal, and this is used as the burst gate pulse.

This is the same as the conventional example. Then, as the input level becomes smaller, the pulse at point g eventually stops appearing.

Therefore, in this embodiment, at point g, berth 1 - a level slightly higher than the human power level at which the gate does not come out is set to the level comparison means 2.
0, and area biB in Fig. 4, that is, the second
In the region where the input chroma signal level is lower than the reference DC voltage level of the comparator 4, the second analog switch 9 is switched to generate a monostable multi-high break having a pulse width CW slightly wider than the burst signal a. The output pulse C is outputted as a burst gate pulse. As a result, even if the human input signal level becomes small, the burst gate pulse will not disappear.

〔Effect of the invention〕

As described above, according to the burst gate pulse generator according to the present invention, when the input signal level is high, a pulse generated from the burst signal is output as a burst gate pulse, and when the input signal is low, a monostable multi-by-break is output. Since the Noj pulse is output as a burst gate pulse, regardless of whether the input signal is large or small,
There is an effect that a burst game pulse is always obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a burst gate pulse generator according to an embodiment of the present invention, FIG. 2 is a diagram showing a conventional gate pulse generator, and FIG. 3 is a diagram showing signal waveforms of each part of FIG. 2. 4 is a diagram showing signal waveforms at various parts in FIG. 1, and FIG. 5 is a diagram showing switching voltages of the second analog switch in FIG. 1. In the figure, 2 is a first analog switch (switch means), 3 is a level detector, 4 is a comparator, 5 is a double-wave rectifier, 6 is a comparator, 8 is a monostable multi-bi break (pulse generating means), 9 2 is a second analog switch (switch means), 20 is a burst gate pulse generating means, and 21 is a level comparing means.

Claims (1)

[Claims] (1) Using the synchronization signal of the television signal as a trigger signal,
pulse generating means for generating a first pulse that can be a burst gate pulse; a first switch means that uses a chroma signal as an input signal and is controlled to open and close by the first burst gate pulse; and an output signal of the analog switch. burst gate pulse generating means for creating a second pulse, which is a burst gate pulse, by comparing the rectified rectified signal with a predetermined level; and a level comparison for comparing the output signal level of the first analog switch with a reference level. means, and the first and second
and second switch means for inputting the pulse and outputting either the first or second pulse as a burst gate pulse according to the output signal of the level comparison means. Pulse generator.