SU427477A1 - DEVICE FOR DIVIDING FREQUENCY FOLLOWING PULSES - Google Patents

Description

one

The invention can be applied in synchronization devices, in television, telemetry, communication systems, etc.

Devices are known for dividing a frequency of pulses with a time selection of input clock pulses by phasing a frequency divider by external human (phase) pulses. Various variants of such devices are used for synchronization in television technology. However, such devices have low noise immunity in the presence of interference on the channel for transmitting external frame pulses (i.e., in the event of random occurrences of false frame and mp pulses and the disappearance of true frame emulses).

It is also known device auth. St. № 277845, providing effective time selection of clock pulses and external frame pulses in the presence of interference on the personnel channel. In this device, noise immunity is provided by a special impulse converter in the form of a series of trigger circuits connected through a coincidence circuit and a pulse counter.

However, the device auth. Ev No. i277845 unjustifiably goes into synchronism in the absence of interference. The duration of the acquisition is determined by the time interval between the first and last trigger of the pulsed trigger.

converter equal to the duration of the frame of the input signal multiplied by the number of triggers of the pulse converter. In addition, with interference at the output of the device in the search mode, false output pulses may appear, which is undesirable in a number of cases.

The purpose of the invention is the elimination of spurious output pulses and acceleration of entering into synchronism in the absence of interference - it is achieved in that the proposed device additionally introduces a key at the output of the frequency divider and a trigger connected through one OR circuit to the first and last triggers of the pulse converter and through the second the circuit "OR -with the first trigger of the converter and the output of the circuit" I. The control input of the key is connected to the trigger, the signal input of the I circuit with the driver, and the control input of the I circuit with the second trigger of the converter. The additionally introduced elements represent a logic circuit that permits the passage of the output pulses of the frequency divider to the output of the entire device when triggered by not only the last, but also the first triggers of the pulse converter. If there is no interference in the time interval before the expected arrival of the second frame pulse, the output of the device

pulses are received from the frequency divider immediately after the appearance of the first personnel pulse. In this case, the timing of the clock pulses is correct. If, however, before the expected arrival of the second personnel pulse, interference pulses are present, the passage of pulses from the frequency divider to the output of the device is prohibited until the pulse converter is fully activated. In the latter case, the device works similarly to the prototype, that is, in the “search” mode with the subsequent transition to the “capture mode”.

As a result, the device acquires adaptive properties, i.e., the acquisition time is determined by the current signal-to-noise ratio and device input, while in the absence of interference, the device immediately switches to the "capture, mine" search mode. In addition, the output pulses of the device at any time point either correspond to the correct time selection or are absent, and the appearance of false output emulsions is eliminated.

FIG. 1 shows a block diagram of the proposed device; FIG. Figures 2 and 3 show timing diagrams explaining the operation of the device under various conditions.

The frequency divider 1 through the key 2 receives the input pulses a. The key is controlled by a pulse converter 3 consisting of trigger circuits, resetting and triggering coincidence circuits, and a pulse counter. For simplicity, FIG. 1 shows only the first 4, second 5 and last 6 triggers necessary for the operation of the device.

Externally, the pulses b, which are supplied to the input through the driver 7 (threshold circuit), pass through a comparison circuit 8 connected to the divider / and the pulse converter 3. The driver 7 is also connected to the pulse converter, including the first trigger 4.

Elements / -8 form a device similar to that described in ed. St. No. 277845.

In addition, a logic circuit formed by the trigger 9 and the control key 10, the input of which is connected to the output of the frequency divider, is included in the proposed device. The trigger 9 is controlled by triggering and resetting via the OR // and 12 schemes, respectively. The “OR //” circuit is connected to the first and last triggers of the converter 5, and the “OR 12” circuit to the first trigger of the converter and through the soviadepi 13 scheme to the driver 7 and the second trigger of the pulse converter.

The device works as follows.

In the search mode, the external frame pulses of b are received at the input of the imager 7, in the general case distorted by interference, so that the appearance of the imager is possible as the appearance of false impulses, as well as the imitation of the true ones.

Consider first the case of no interference. When the first personnel pulse arrives, a pulse appears at the output of the imaging unit, the trailing edge of which triggers the first trigger 4 of the pulse converter 5. As a result, the key 2 opens and the input pulses to be divided and arrive at the frequency divider 1. At the same time, the pulse corresponding to the trigger transition 4, it launches through the "OR 11 trigger 9" scheme, which opens the key 10. Because io: there are no mechs, the reset pulses to the trigger 9 are not received, the key 10 remains open, and the output impulses sy frequency divider 1 arrive at the device output. In this case, the first pulse at the output appears after the arrival of the first frame pulse b after an interval of time equal to the duration of one frame.

Thus, the device enters the "capture mine mode" search. The pulse converter works in this case.

similar to the device on auth. St. No. 277845, i.e., the converter triggers are triggered successively up to trigger 6, the differential pulse from which is sent through the OR 11 circuit to trigger trigger 9, i.e.

confirms the state of the latter.

The differential of the second trigger 5, controlled by the coincidence circuit 13, eliminates the possibility of resetting the trigger 9 through the scheme OR 12 by the falling edge of the next pulse from the driver 7.

In the presence of Iomeh on the channel of transmission of a personnel pulse, the device works differently. Upon receipt of the first pulse b, the output of the former 7 also appears

a pulse (it can correspond to both true and horizontal frame impulses), the falling edge of which triggers the first trigger 4. As well as, the key 2 opens, the trigger 9 starts, the pulses go through

divider /, and key 10 opens. Odiaco, with interference, the emulsion at the output of shaper 7 appears before the expected arrival of the next frame pulse b, i.e., until the second trigger 5 is activated. Therefore

the leading edge of the pulse from the imaging unit 7 passes through the AND 13 circuit and then through the P1LI 12 circuit to reset the trigger 5. The key // is closed and no pulses are output from the divider / to the device output.

Key 10 then opens only after trigger I trigger, which can occur only after trigger trigger 6 of the pulse converter, which is triggered only as a result of the completion of the device search mode, similar to that of auth. St. AIO 277845. In this mode, the period of following external frame pulses is checked with the help of a pulse converter for equality to the period following the output pulses of frequency divider 1 (“search” mode). If this equality is fulfilled for a certain number (determined by the number of triggers in the pulse converter) of the following extra-vertical frame impulses, the frame impulse is considered true, and the device switches to the capture mode. In this case, the divider remains in the phased state, i.e., the output pulses of the frequency divider coincide in phase with the external frame pulses. Thus, time selection of clock pulses on external personnel pulses occurs.

In the “capture mode”, false frame pulses do not affect the operation of the device. If the same in this mode, the personnel pulses are lost, then, with a certain number of pulse drops, the device again goes into the “search” mode. The number of interruptions is determined by the capacity of the pulse counter (shown in Fig. 1, ne is shown) included in the pulse converter and the number of triggers in the same converter.

When switching to the search mode, the first trigger 4 of the converter is reset and its front through the scheme OR // resets the trigger 9. The key 10 is closed, which eliminates the appearance of spurious emulses at the output of the search mode.

As a result, a minimum time to synchronization is obtained in the absence of interference, high noise immunity in the presence of interference, and false pulses at the output of the device are excluded in the "search" mode.

FIG. 2 shows a timing diagram of the operation of the device in the absence of interference on the transmission channel of external pulses 8.

FIG. 3 shows a time diagram of the operation of the device in the presence of interference. False impulses at the output of the former 9 are marked by two lines near the top.

Subject invention

A device for dividing the frequency of a pulse pulse according to aut. St. No. 277845, characterized in that, in order to eliminate spurious output emulsions and accelerate synchronization entry in the absence of interference, it contains a key at the output of a frequency divider, a trigger, two circuits ILR1 and an And circuit, and the trigger inputs are connected through one circuit "OR with the first and last triggers of the converter and through the second circuit

“OR — with the first trigger of the converter and the output of the AND circuit, the control input of the key is connected to the trigger, the first input of the AND circuit is connected to the driver, and the second to the second trigger of the converter.

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