JPH06140925A - Phase synchronization equipment - Google Patents

Abstract

PURPOSE:To compare phases at a horizontal synchronizing frequency with simple circuit configuration. CONSTITUTION:The equipment is provided with a phase shift circuit 2, a switch circuit 4 and divides an oscillating frequency of an oscillator 1 into plural phases and a signal of each phase is sequentially switched by the switch circuit 4 and the result is outputted to a frequency divider 5, the phase of the output of the frequency divider 5 and the output phase of a crystal oscillator 9 being the other oscillator are compared by a phase comparator 7 and a comparison output of the phase comparator 7 controls the oscillating frequency of the oscillator 1 and controls the oscillating frequency of the other oscillator, then the phase comparison in a horizontal synchronizing frequency is implemented by using the frequency dividers 5 of less number of stages.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase synchronizer, and more particularly to a phase synchronizer for synchronizing oscillation frequencies among a plurality of oscillators.

[0002]

2. Description of the Related Art Conventionally, in a color television system of the NTSC system, for example, in a synchronizing relationship of video signals, a pulse signal such as a horizontal synchronizing signal is set with a frequency four times as high as a color subcarrier frequency (hereinafter referred to as fsc) as a reference. Synchronous ICs are commonly used.

Using such a synchronization IC, a video image digitized at a sampling frequency fs which is not a frequency 4fsc series which is four times the color subcarrier frequency is D
When A-converting and outputting as a video signal, it is necessary to synchronize the phase relationship between the frequency 4fsc and the sampling frequency fs. Therefore, the sampling frequency f
As s, for example when choosing a half-integer multiple of the horizontal synchronizing frequency f _H, so that the performing phase comparison at a frequency of half of 1 / 2f _H horizontal synchronizing frequency f _H.

[0004]

In the above prior art,
Since a frequency divider with a very large number of stages is required to convert the horizontal synchronizing frequency f _H into a frequency of 1/2, there is a problem that the circuit configuration of the synchronizing device becomes complicated. Also,
There is a problem that the control band of the phase locked loop becomes low and the response characteristics deteriorate. The present invention has been made in view of the above problems, and an object thereof is to enable phase comparison at a horizontal synchronizing frequency with a simple circuit configuration.

[0005]

A phase synchronization device of the present invention is a phase synchronization device configured to synchronize oscillation phases among a plurality of oscillators, among signals output from the plurality of oscillators. Phase shift means for distributing an output signal of an oscillator into a plurality of phases for output, and one of a plurality of signals having different phases by the phase shift means.
Selecting means for selecting and outputting one of the two, and dividing means for dividing the signal selected by the selecting means,
And a phase comparator for comparing the phases of these two input signals with the output signal of the frequency dividing means and the output signal of the other oscillator, and according to the comparison result of the phase comparator, The oscillation frequency of a certain oscillator or the oscillation frequency of the other oscillator is controlled.

[0006]

According to the present invention, the sampling frequency fs is divided into a plurality of phases before being input to the frequency divider, and the signal of each phase is sequentially switched so that the frequency division is performed by an integer. The number of stages of the frequency divider is small, and the phase comparison can be performed at the horizontal synchronizing frequency with a simple circuit configuration.

[0007]

1 is a block diagram showing the configuration of an embodiment of a phase synchronization apparatus of the present invention. In FIG. 1, 1 is a voltage controlled crystal oscillator, 2 is a phase shift circuit, 3 is an inverting circuit,
The output of the voltage controlled crystal oscillator 1 is input to the phase shift circuit 2 and the inverting circuit 3, respectively. The outputs of the phase shift circuit 2 and the inverting circuit 3 are input to the switch circuit 4, respectively, and the output of the switch circuit 4 is input to the frequency divider 5.

Next, 6 is a flip-flop circuit, 7 is a phase comparator, and the output of the frequency divider 5 is supplied to these flip-flop circuit 6 and phase comparator 7. Further, the output of the flip-flop circuit 6 is supplied to the switch circuit 4, and the operation of the switch circuit 4 switching between the phase shift circuit 2 and the inverting circuit 3 for output is controlled by the output of the flip-flop circuit 6. It is configured.

Reference numeral 8 is a loop filter, to which the output of the phase comparator 7 is supplied. The output of the loop filter 8 is the voltage controlled crystal oscillator 1
It is supplied as a control signal of. Further, 9 is a crystal oscillator, 10 is a frequency divider, and the output of the crystal oscillator 9 is input to the phase comparator 7 through the frequency divider 10.

Next, the operation of the phase synchronizer of this embodiment will be described with reference to the waveform diagram of FIG. In FIG.
(A) shows the output of the phase shift circuit 2 and (b) shows the output of the inverting circuit 3. Further, (c) is an output of the frequency dividing circuit 5, (d) is an output of the flip-flop circuit 6, and (e) is an output of the switch circuit 4.

At time point A in FIG. 2, the switch circuit 4 selects the output (b) of the inverting circuit 3. Then, the frequency division is completed at the rise of the output (b) of the inverting circuit 3, and the pulse (c) is output from the frequency division circuit 5.

In response to the pulse (c) output from the frequency dividing circuit 5, the flip-flop circuit 6 outputs
The signal having the waveform of (d) is output. As a result, the switch circuit 4 selects and outputs the output of the phase shift circuit 2, and the output (e) of the switch circuit 4 switches to the opposite phase. Then, at the next time point B, the output of the phase shift circuit 2 (a)
In response to the rising edge of, the frequency dividing circuit 5 starts the next counting.

Next, the frequency dividing circuit 5 counts up to time C and outputs the frequency division result at the third count. Then, the output (d) of the flip-flop circuit 6 is inverted corresponding to the pulse of the frequency dividing circuit 5 after the time point C, and the switch circuit 4 selects the output (b) of the inverting circuit 3. By repeating the above operation, a signal obtained by dividing the frequency of the voltage controlled crystal oscillator 1 into 1/2 is obtained at the output (c) of the frequency dividing circuit 5. Then, this signal (c) is input to the phase comparator 7 and phase synchronization is performed.

Next, a second embodiment of the phase synchronizer of the present invention will be described with reference to the block diagram of FIG. Note that, in FIG. 3, the same parts as those in FIG. As shown in FIG. 3, in the second embodiment, the first transfer circuit 2 and the second transfer circuit 1 are used as the transfer circuits.
Three phase shift circuits, that is, the first and third transfer circuits 12 are provided. Further, in this embodiment, the switch circuit 14 for selecting and outputting one signal from the three inputs is provided.

In the second embodiment thus constructed, the output of the voltage controlled crystal oscillator 1 is converted into three phase shift circuits 2,
11 and 12, and outputs the outputs of these phase shift circuits to the switch circuit 14. Then, the output selected by the switch circuit 14 is given to the frequency dividing circuit 5.

The output of the frequency dividing circuit 5 is converted into a 2-bit switch signal which repeats in three cycles by the pulse converting circuit 15 and is input to the switch circuit 14. As a result, a signal whose phase is shifted by 1/3 cycle is output to the switch circuit 1.
It is possible to sequentially switch and output with 4, and by inputting this to the frequency divider 5, a frequency division output of (integer value + 1/3) is obtained.

That is, as shown in this second embodiment,
By providing N phase shift circuits, the original oscillation frequency can be reduced to 1 /
The frequency can be divided into N, and the phase comparison of (integer value + 1 / integer) can be performed by a simple circuit.

[0018]

As described above, according to the present invention, the phase shift circuit and the switch circuit are provided, the original oscillation frequency is divided into a plurality of phases, and the signals of each phase are sequentially switched and output. The frequency division of (M + 1 / N) can be realized with a simple circuit configuration. Therefore, it is possible to perform phase comparison at the horizontal synchronizing frequency even with a frequency divider having a small number of stages, and it is possible to realize a phase synchronizing apparatus having a simple circuit configuration.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a phase synchronization device showing a first embodiment of the present invention.

FIG. 2 is a waveform diagram for explaining an operation of each unit of the phase synchronizer of FIG.

FIG. 3 is a configuration diagram of a phase synchronization device showing another embodiment of the present invention.

[Explanation of symbols]

 1 Voltage Control Crystal Oscillator 2 Transfer Circuit 3 Inversion Circuit 4 Switch Circuit 5 Frequency Divider 6 Flip-Flop Circuit 7 Phase Comparator 8 Loop Filter 9 Crystal Oscillator 10 Frequency Divider 11 Transfer Circuit 12 Transfer Circuit

Claims (2)

[Claims] 1. A phase synchronizer configured to synchronize oscillation phases among a plurality of oscillators, wherein among the signals output from the plurality of oscillators,
Phase shift means for distributing and outputting an output signal of a certain oscillator into a plurality of phases, and selection for selecting and outputting one of the plurality of signals whose phases are made different by the phase shift means. Means, frequency dividing means for dividing the signal selected by the selecting means, and the output signal of the frequency dividing means and the output signal of the other oscillator, and the phases of these two input signals. And a phase comparator for comparing the oscillation frequency of the one oscillator and the oscillation frequency of the other oscillator according to the comparison result of the phase comparator. 2. The phase synchronizer according to claim 1, wherein the phase of the signal selected by the selecting means is switched according to the signal obtained by dividing the output of the selecting means.