JPH08111788A - Synchronizing signal generation system - Google Patents

Abstract

PURPOSE: To acquire a color synchronizing signal that is free from the color jitters and the phase drift by using an input SC(subcarrier) signal of high stability, if available, as an output SC signal and then using a reproduced SC signal of an internal oscillator output if the input SC signal is not available. CONSTITUTION: The presence or absence of an input signal is detected at an input signal detection part 102 of a synchronizing signal generation device. When an input SC signal is confirmed, the output of a switch part 109 is used as an input SC signal. When no input SC signal is confirmed, the switching control is applied to a 1/4-counter part 106 in order to acquire an SC signal of its on station. Therefore the input SC signal of high stability, if available, is used as an output SC signal as it is so that a stable SC signal that is free from the color jitters and the phase drift can be acquired.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color television synchronizing signal generating system.

[0002]

2. Description of the Related Art FIG. 2 shows an example of a conventional color television synchronizing signal generating system. 201 is an input buffer unit, 2
Reference numeral 02 denotes an input signal detection unit, 203 denotes a phase comparison PLL unit, 2
04 is a switch unit, 205 is a voltage-controlled crystal oscillator,
206 is a 1/4 counter section, 207 is a pulse generating section for generating each synchronization signal, and 208 is CB (color bar signal) /
This is a BB (black burst signal) generator. The high frequency precision subcarrier (SC) signal output from the Rubidium oscillator is input to the input buffer 201, and the PLL unit 203
Then, the phase comparison error signal is phase-compared with the local SC signal of the 1/4 counter unit 206, and the phase comparison error signal controls the SC signal output (4 fsc) that is four times as high as that of the crystal oscillator 205 through the switch unit 204 to control the local station. Synchronize the SC signal with the input SC signal.
Further, the 4fsc clock signal of the crystal oscillator 205 is input to the pulse generation unit 207, and each synchronizing signal and CB /
The BB generator 208 obtains test signals such as color bar signals and black burst signals.

In this prior art, the output SC signal is a PLL.
Since it is obtained by the synchronous reproduction method, the jitter due to the synchronous coupling, the phase drift due to the ambient temperature change and the secular change occur, and the input SC signal which is the highly stable Rubidium oscillator output is used, but the reproduction is performed. The SC signal becomes a problem in stability, and there is a demand for an SC signal having less jitter and no phase fluctuation.

[0004]

In the above-mentioned prior art, since the output SC signal is produced by the PLL synchronous reproduction system,
Synchronous coupling jitter is a problem because it has phase fluctuations. An object of the present invention is to eliminate these drawbacks and to always output a stable synchronization signal.

[0005]

In order to achieve the above object, the present invention uses the input SC signal as it is as the output SC signal when there is a highly stable input SC signal, and when there is no input SC signal. Is to obtain a color sync signal free from color jitter and phase drift by using the reproduced SC signal output from the internal oscillator.

[0006]

As a result, as the output subcarrier (SC) signal, when the input SC signal is present, the highly stable input SC signal is used as it is, and when there is no input SC signal, the SC of the own station from the internal oscillator is used. Since the signal is used, it is possible to obtain a color synchronization signal without color jitter and phase drift.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. Reference numerals 101 to 108 are 20 shown in the conventional embodiment of FIG.
The same as 1 to 208. 109 is a switch unit.
The input signal detection unit 102 detects the presence or absence of an input signal. When the input SC signal is present, the output of the switch unit 109 is used as the input SC signal, and when the input SC signal is not present, the 1/4 counter unit 106 is used. The switching control is performed so that it becomes the subcarrier (SC) signal of its own station. This ensures a highly stable input S
When there is a C signal, the input SC signal is used as it is as the output SC signal, so that a stable SC signal can be obtained without color jitter or phase fluctuation.

[0008]

According to the present invention, a stable color synchronizing signal (SC) can be obtained only by adding a switch section before the output of the output SC signal.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing a conventional embodiment.

[Explanation of symbols]

 101 input buffer unit 102 input signal detection unit 103 PLL unit 104 switch unit 105 crystal oscillator 106 1/4 counter unit 107 pulse generation unit 108 CB / B.B generation unit 109 switch unit

Claims (1)

[Claims] 1. A synchronizing signal generation system for reproducing various synchronizing signals by inputting a subcarrier signal output from a high-precision Rubidium oscillator, and when there is an input subcarrier signal, the input subcarrier signal is output as it is. Synchronous signal generation method, which is used as a signal and uses the reproduced subcarrier signal of the internal oscillator output when there is no input subcarrier signal.