JPS63245127A - Phase locked loop system - Google Patents

Abstract

PURPOSE:To allow the titled system to withstand a momentary noise by using a horizontal synchronizing signal as a reference signal and a 1st phase locked loop signal of the same frequency as a reference signal so as to output a 2nd phase locked loop signal with a frequency higher than that of the horizontal synchronizing signal. CONSTITUTION:A horizontal synchronizing signal is separated from a television composite video signal given from a terminal 52 at a synchronizing separator circuit 2 and given to a phase comparator 3 as a reference signal corresponding to a 1st phase locked loop. The oscillation output signal of a voltage controlled oscillator (I) is given to a phase comparator 7 as a reference signal to a 2nd phase locked loop. An output signal of a voltage controlled oscillator (II) 5 is outputted from a terminal 51 as a synchronizing signal having a high frequency being n-times of the horizontal synchronizing signal. The circuit is stable against fluctuation such as temperature by the double phase locked loop and withstands a momentary pulse noise and a high frequency signal synchronized with the horizontal synchronizing signal is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a phase synchronization system, and more particularly to a phase synchronization system for generating a high frequency signal that is phase synchronized with a horizontal signal of a television composite video signal.

[Conventional technology]

Conventionally, this type of phase synchronization method, as an example shown in FIG. A phase-locked loop is formed by the above, and the output from the synchronous separation circuit 9 is input to the phase comparator 11.

In FIG. 2, a television video signal input from a terminal 53 is separated into a horizontal synchronization signal by a synchronization separation circuit 9 and outputted, and the horizontal synchronization signal is inputted to a phase comparator circuit 11 as a reference signal for phase synchronization. Ru. On the other hand, the oscillation output signal of the voltage controlled oscillator 13 has its frequency divided by l/n (n is a positive integer) by the frequency divider 10, is input to the phase comparator 11, and is compared in phase with the reference signal. In the phase comparison circuit 11, a phase difference signal between the oscillation output signal and the reference signal is output, and is input to the voltage controlled oscillator 13 via the low-pass filter 12. The frequency and phase of the oscillation output signal of the voltage controlled oscillator 13 are controlled to be n times the frequency and phase of the horizontal synchronization signal output from the synchronization separation circuit 9 through the action of the phase locked loop. In other words, a phase-synchronized high-frequency signal with a frequency n times that of the horizontal synchronization signal of the TV composite video signal is
, obtained as the oscillation output of the E-pressure controlled oscillator 13.

[Problem that the invention seeks to solve]

In the above-mentioned conventional phase synchronization method, the voltage controlled oscillator configured with the CMO8 integrated circuit has a problem in that the free run frequency has a large variation with respect to fluctuations in temperature and power supply voltage, and also has a high oscillation frequency.
High gain or not obtained.

Therefore, in order to construct a stable phase-locked loop with a high output oscillation frequency without causing loss of phase synchronization due to temperature fluctuations, etc., in the conventional single phase-locked loop, the gain of the low-pass filter is It is necessary to increase the phase complementation range and set the phase supplementation range widely. However, when using a low-pass filter with a large gain, the speed of the phase-locked loop that follows changes in the reference input frequency is too fast, making the phase-locked loop weak against instantaneous noise. There are drawbacks.

[Means for solving problems]

The phase synchronization method of the present invention includes a first phase synchronization loop that uses a horizontal synchronization signal of a predetermined television composite video signal as a reference signal and outputs a first phase synchronization signal having the same frequency as the horizontal synchronization signal; a second phase-locked loop that uses the first phase-locked signal as a reference signal and outputs a second phase-locked signal having a higher frequency than the frequency of the horizontal synchronization signal.

〔Example〕

Next, 1) and 2 will be explained regarding the present invention with reference to the drawings.

FIG. 1 is a block diagram showing the main parts of an embodiment of the present invention. As shown in FIG. 1, in this embodiment, a voltage controlled oscillator (■) 1, a phase comparator circuit 3, and a low-pass filter 4 form a first phase-locked loop, and a second phase-locked loop forms a second phase-locked loop. a voltage controlled oscillator (II) 5, a frequency divider 6, a phase comparison circuit 7, a low-pass filter 8, and a synchronous separation circuit 2.
It is equipped with.

In FIG. 1, a television composite video signal inputted from a terminal 52 is separated into a horizontal synchronization signal by a synchronization separation circuit 2, and the horizontal synchronization signal is sent to a phase comparator circuit 3 as a reference signal corresponding to a first phase-locked loop. is input. 1st
The phase-locked loop voltage controlled oscillator (■) 1 has a low oscillation frequency, but is configured to generate an oscillation output signal that is stable against fluctuations such as temperature and power supply fluctuations,
A signal whose phase is synchronized with the horizontal synchronization signal output from the synchronization separation circuit 2 is output. The oscillation output signal of the voltage controlled oscillator (I) 1 is input to the phase comparison circuit 7 as a reference signal for the second phase-locked loop.

The voltage controlled oscillator (n) 5 of the second phase-locked loop has a high oscillation frequency as in the conventional example, but has a characteristic that the frequency shift is large with respect to fluctuations in humidity, power supply voltage, etc.
For this reason, the phase complement range of the second phase-locked loop is set wide. This second phase-locked loop is phase-locked to the oscillation output signal of the voltage-controlled oscillator (■) 1 in the first phase-locked loop, and the frequency divider 6 has a frequency division function of 1/n. Then, the voltage controlled oscillator (■)
The output signal No. 5 is outputted via the terminal 51 as a synchronization signal having a frequency n times as high as that of the horizontal synchronization signal.

In the double phase-locked loop, the synchronous separation circuit 2
The ability to follow the horizontal synchronization signal output from
It depends on the low-pass filter characteristics of the first phase-locked loop. That is, in the first phase-locked loop,
Since the voltage controlled oscillator (I) 1 has high temperature stability, it is possible to freely set the low-pass filter characteristics related to the phase complementary range. Therefore, by setting the low-pass filter characteristics, the first phase-locked loop can be formed as a phase-locked loop that is strong even against instantaneous noise. Moreover, the second phase-locked loop outputs an oscillation signal of n times the frequency using the oscillation output signal of the voltage-controlled oscillator (■) 1 of the first phase-locked loop as a reference signal. It is clear that this double phase-locked loop provides a high-frequency signal synchronized with the horizontal synchronization signal that is stable against fluctuations in temperature, etc., and resistant to instantaneous pulse noise. be.

〔Effect of the invention〕

As described above, the present invention is applied to a phase synchronization method corresponding to a horizontal synchronization signal of a television composite video signal, and uses the horizontal synchronization signal as a reference signal to generate a first phase signal having the same frequency as the horizontal synchronization signal. a first phase-locked loop that outputs a synchronization signal; and a second phase-locked loop whose frequency is higher than the frequency of the horizontal synchronization signal, using the first phase-locked signal as a reference signal.
A second phase-locked loop that outputs a phase-locked signal of The effect is that it can be formed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the main parts of an embodiment of the present invention, and FIG. 2 is a block diagram showing the main parts of a conventional phase synchronization system. In the figure, 1...voltage controlled oscillator (I), 2...
. 9... Synchronization separation circuit, 3, 7.11... Phase comparison circuit, 4.8.12... Low pass filter, 5... Voltage controlled oscillator (n), 6.10... Min. Frequency generator, 13...voltage controlled oscillator.

Claims (1)

[Claims] a first phase-locked loop that uses a horizontal synchronization signal of a predetermined television composite video signal as a reference signal and outputs a first phase-synchronization signal having the same frequency as the horizontal synchronization signal; and a second phase-locked loop that outputs a second phase-locked signal having a frequency higher than the frequency of the horizontal synchronization signal.