SU1746321A1 - Device for determining polarity of periodic pulse video pulses - Google Patents

Abstract

The invention relates to electronics and can be used to determine the polarity of periodic pulsed video signals. A device for determining the polarity of periodic pulsed video signals contains a coupling capacitor 1, inverting and non-inverting symmetric limiting amplifiers 2 and 3. Low-pass filters 4 and 5, a unit 6 for determining the signal module, a reference voltage source 7, a comparator 8. Electronic switch 9 and polarity indicator 10. 3 il.

Description

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The invention relates to electrical engineering and can be used to determine the polarity of periodic pulsed video signals.

A device for determining the duty cycle of periodic pulsed video signals is known, comprising a coupling capacitor, two DC amplifiers, two peak detectors, two resistors and a polarity indicator, in which the coupling capacitor is connected between the input of the device and the inputs of the DC amplifiers, the inputs of the first and second peak the detectors are connected to the outputs of the first and second amplifiers of direct current, respectively, and the outputs, respectively, through the first and second resistors with the indicator input on lnness.

A disadvantage of this device is the low accuracy of determining the polarity of the pulsed video signals when they are very long, due to the fact that when signals are monitored at a high rate, the signal level at the indicator input is commensurate with noises, which with great probability can cause an error in polarity determination.

The closest in technical essence of the invention is a device for determining the polarity of periodic pulsed video signals, comprising a coupling capacitor, a symmetric limiting amplifier, a low-pass filter and a polarity indicator connected in series with the device input.

A disadvantage of the known device is a narrow range of controlled signals. It is due to the fact that at a signaling ratio of a monitored signal close to two, the signal level at the output of the low-pass filter is comparable to noise, which with a high probability can cause an error of polarity determination, and at a signaling ratio of less than two, the polarity error inevitable even in the absence of noise.

The purpose of the invention is to expand the field of use by providing control of the polarity of signals with a wide range of duty cycles.

The goal is achieved in that a device for determining the polarity of periodic pulsed video signals, containing a polarity indicator and a separation capacitor, a first symmetrical limiting amplifier and a first low-pass filter, are in series connected to an electronic switch, a voltage source, and connected to the input of the device is a second symmetric amplifier-limiter,

the second low-pass filter, the module for determining the signal module and the comparator, the second input of the comparator is connected to the output of the reference voltage source, and the output is connected to the control input of the electronic switch, the first and second information inputs of which are connected to the outputs of the first and second low-pass filters, respectively and the output is with the input of the polarity indicator.

5 In FIG. 1 shows a block diagram of the proposed device; in fig. 2 and 3 are time diagrams that show his work.

The device for determining the polarity of the periodic pulse signals contains a coupling capacitor 1, inverting 2 and non-inverting 3 symmetrical limiting amplifiers, filter G4 and 5 low frequencies / unit 6 determining the signal module, reference voltage source 7, comparator 8, electronic switch 9 and polarity indicator 10. The input of the device is connected via a capacitor 1 to the input of the amplifier - limiter 2 and directly to the input of amplifier 3. Filter 4 is connected between the output of the amplifier limiter 2 and the first information input of the switch 9. Filter 5 is connected between the output of force5 of the limiting body 3 and the second information input switch 9. whose control input is connected to the output of the comparator 8, and the output to the input of the indicator 10. Block 6 is connected between the output of the filter

0 5 and the first input of the comparator 8, the second input of which is connected to the output of the source 7..

The device works as follows.

5 A periodic input signal (Fig. 2, Over}, representing, for example, a sequence of rectangular pulses of positive polarity with amplitude E and duty cycle Q, is fed from the input of the device through the capacitor 1 to the input of the amplifier-limiter 2 and directly to the input of the amplifier - limiter 3.

When passing through the capacitor 1, the input signal loses the constant component, is shifted relative to the zero level and turns into a two-pole signal (Fig. 2.36). The amount of displacement (constant component) depends on the shape, amplitude E and the duty cycle Q of the input signal. With rectangular input signal

the offset U0 is E / Q, and the amplitudes of the positive U + and negative U- components of the signal at the input of limit amplifier 2 are determined as follows:

(1-1 / Q);

U- U0 E / Q. So when Q 5 (figa) receive

U0 Ц- «0,2 Е; U + 0.8 E (figb),

and at Q 1.25 (Fig. For)

Uo U- - 0.8 E; C + 0.2 E (Fig. 36). The threshold Eo of the limiting in x-limiting amplifiers 2 and 3 is chosen as large as possible for the amplitude of the input signal. The limiting amplifier 3 converts the input signal (Fig. 2, 3a) into a square signal of the same polarity and duty cycle with amplitude Eo (Fig. 2, 3b). The signal from the output of the amplifier-limiter 3 is fed to the input of the filter 5, which selects a constant component of this signal (Fig. 2.3g). This component has the same polarity as the input signal. Its level is E0 / Q. It is greater, the smaller the duty cycle Q of the input signal, but does not exceed the level Eo. At 0 3, this level is. E0 / 3. The signal from the output of the filter 5 is fed to the input of block 6 and to the second information input of switch 9.

The limiting amplifier 2 converts the signal at its input (Fig.2.36) into an inverse opposite polarity signal with the same amplitudes of the positive and negative components (Fig.2.3d). The signal from the output of the amplifier-limiter 2 is fed to the input of the filter 4. which selects the constant component of this signal (Fig. 2.3f). This Q 2 component has the same polarity as the input signal. Its level is Eo (1-2 / Q). It is greater, the greater the duty cycle Q input signal, but does not exceed the level E0. At 0 3, this level is E0 / 3. The signal from the output of the filter 4 is fed to the first information input of the switch 9.

Block 6 generates a positive polarity signal (Fig. 2.3g), equal in strength to the signal from the output of the filter 5. The signal from the output of the filter 5 is fed to the information input of the comparator 8, to the reference input of which a constant signal of level Eo / 3 is received (Fig 2,3zh, dashed) from the output of the source 7. Comparator 8, in the case of continuous

.Over the signal at the output of the block 6 level Eo / 3, generates a signal, under the action of which the switch 9 connects to the input of the indicator 10 the output of the filter 4 (Fig. 2h), and if the signal at the output of the block b exceeds the level Eo / 3 produces a signal under the action of which the switch 9 connects to the input of the indicator the output of the filter 5 (Fig. 3).

Thus, in the proposed device, at any duty ratio Q of the input signal at the input of the indicator 10, there is a signal whose polarity is the same as that of the input signal, and the level is not less than E0 / 3. At Q5: 3, this signal is formed by filter 4, and at Q 3 it is formed by filter 5. This ensures that at any Q-factor of the input signal, the signal level at the input of the indicator 10 is much higher than the noise level, which makes it possible to reliably determine the polarity of the input signal.

In the known device, a high level of the signal at the input of the polarity indicator is provided only at Q3. This significantly expands the range of the boreholes of the monitored signals in the proposed device as compared to the known one.

Claims (1)

Invention Formula A device for determining the polarity of periodic pulsed video signals, comprising a polarity indicator and a coupling capacitor, a first balanced amplifier-limiter and a first low-pass filter, connected in series with the input of the device, characterized in that in order to expand the field of use by monitoring the polarity of signals with a wide range of duty cycles, an electronic switch, a reference voltage source and connected in series with the device input are introduced into it A second balanced amplifier, a second low-pass filter, a signal module determining unit and a comparator, the second input of the comparator is connected to the output of the reference voltage source, and the output to the control input of the electronic switch, the first and second information inputs of which are connected respectively to the outputs of the first and the second low-pass filters, and the output with the input of the polarity indicator. p p p p p about pn o well u fold Editor N. Bobkova Tehred M. Morgenthal Order 2393. Circulation: Subscription VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk emb. 4/5 f. . feff-g / c) Proofreader L. Beskid