JPH0198394A - Signal processor - Google Patents

Abstract

PURPOSE:To attain quick phase correction by adopting the constitution such that either a signal from an input terminal or a signal being the result of prescribed phase shift of the output of a delay means is given to the input of the delay means so as to improve the tracking performance of the entire system. CONSTITUTION:A switch 1 is changed over by a controller 2. In throwing the switch 1 to the position (a), the signal from an input terminal 3 is given to a subtractor 4 and a delay means 5. The output of the delay means 5 is given to the subtractor 4 and the signal being the result of subtracting the output signal of the delay means 5 from the signal from the input terminal 3 becomes an output of the subtractor 4 and outputted from an output terminal 6. In throwing the switch 1 to the position (b), the output of the delay means 5 is shifted by a prescribed quantity at a phase shifter 7 and inputted to the delay means 5 and a signal phase-shifted by prescribed quantity each is outputted from the delay means 5 at each prescribed delay time.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a signal processing device used in video equipment and the like.

2. Description of the Related Art An example of a conventional signal processing device is shown in FIG.
FIG. 3 is a block diagram of a reproduced color signal demodulator of TR. terminal 31
The reduced converted color signal from the oscillator 32 and the output of the voltage controlled oscillator 32 are both input to the frequency converter 33, and the output of the zero frequency converter 33 from which the carrier color signal output is obtained is transferred to the IH delay element (H: horizontal scanning period) 34. The signal is input to a comb filter 36 composed of a subtracter 35 and a subtracter 35, and a signal from which crosstalk components have been removed is output to a terminal 37. <C type filter 3
The burst signal portion of the output signal of 6 and the output signal of the crystal oscillator 38 are phase-compared in a phase comparator 39, and the error detection voltage is input to the voltage controlled oscillator 32. type filter 36,
The phase comparator 39 and the voltage controlled oscillator 32 are connected to P L L (
Phase Locked Loop). As a result, an output whose phase is synchronized with the output signal of the crystal oscillator 38 is obtained at the output terminal 37.

However, in the above configuration, for example, a 4-head VT
During a noiseless high-speed search for R, etc., if the input of the low-frequency conversion color signal becomes discontinuous and the output signal from the terminal 37 becomes asynchronous with the output signal from the crystal oscillator 38, it will take some time before synchronization is achieved again. takes 2 to 8 hours. FIG. 4 schematically shows the relative phase relationship among the input of the comb filter 36, the output of the IH delay element 34, and the output of the subtracter 35 for each IH at this time.

In FIG. 4, the direction of the arrow indicates the phase of a signal (for example, a burst signal) having the same phase on each scanning line. In reality, the color signal is inverted for each IH, but in order to make the diagram easier to read, phase inversion is not considered here. It is assumed that the phases of the arrows are synchronized when they point directly to the right, and t is the time axis. Assume now that the hesodon amplifier is switched at 1=10, and the input signal becomes discontinuous. Actually, since the color signal is inverted for each IH, the output of the subtracter 35 is the vectorial sum of the input of the comb filter 36 and the output of the IH delay element 34. As can be seen by comparing the input of the comb filter 36, that is, the output of the frequency converter 33, and the output of the subtracter 35, after the phase of the input signal becomes discontinuous, the phase of the output signal of the subtractor 35 is not very accurate. Don't turn to the right. This is because even if the phase comparator 39 and the voltage controlled oscillator 32 reduce the phase error, it is vectorially added to the phase before IH. From another perspective, it can be said that the comb filter suppresses tracking of the phase of the system excluding the comb filter.

Problems to be Solved by the Invention In such a conventional signal processing device, when the input signal becomes discontinuous, the output phase of the comb filter has a larger phase error than the input phase, except for the IH immediately after switching. becomes large, and the phase tracking performance of the entire system is not very good.

In view of these points, it is an object of the present invention to provide a phase synchronization device that has good follow-up performance of the entire system and allows prompt phase correction.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention uses a changeover switch as shown in FIG. It has a configuration in which one of the matching signals is used.

According to the above-described configuration, the present invention uses the signal immediately before the discontinuity or the signal obtained by shifting the phase thereof by a predetermined amount for a predetermined period immediately after the input signal to the system becomes discontinuous as the manual input of the subtracter. , phase correction is also performed in the subtractor, resulting in better tracking performance between phases! tlI device configuration is possible.

Embodiment Hereinafter, a reproduced color signal demodulator according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the principle of the present invention. Switch 1 is switched by controller 2. When the switch 1 is connected to the a side, the signal from the input terminal 3 is input to the subtracter 4 and the delay means 5. The output of the following means 5 is input to the subtracter 4, and the signal obtained by subtracting the output signal of the delay means 5 from the signal from the input terminal 3 becomes the output of the subtracter 4, and is output from the output terminal 6. When the switch l is connected to the b side, the output of the delay means 5 is phase-shifted by a predetermined amount by the phase shifter 7 and inputted to the delay means 5, so that the output of the delay means 5 is output by a predetermined amount at every predetermined delay time. A signal whose phase is shifted by 1.0 is output.

Next, FIG. 2 shows an embodiment of the present invention. FIG. 2 shows a color signal demodulator using the signal processing device 1) of the present invention in place of a conventional comb filter. Normally, the switch 12 is connected to the a side, and the processing device 13 (1) has the same function as a rectangular filter.The 2H counter 13 detects the rising and falling edges of the negative amplifier switching pulse from the terminal 14 during high-speed search. is detected and the switch 12 is switched to the b side for a period of 2H.The output of the IH delay element 15 is input to the subtracter 16 and 180@phase shifter 17, so the subtracter 16 switches the switch 12 to the b side. IH just before
A signal inverted for each IH is input. As before, the relationship between the input of the signal processing device f12, the output of the IH delay element 15, and the output of the subtracter 16 at this time is expressed as
As shown in the figure.

1=1. It is assumed that the edge of the head amplifier switching pulse is detected at and the switch 12 is connected to the b side during the 2H period up to 1-1). By comparing the input of the signal processing device 1) and the output of the subtracter 16, it can be seen that phase correction is performed in the subtracter. Also, if you compare it with Figure 4, switch 1
It can be seen that the tracking performance of the system after connecting No. 2 to the b side exceeds that of the conventional system. Here, the reason why the time for switching the switch 12 to the b side is set to 2H is as follows. If the time to switch to the b side is made longer, the phase tracking performance will improve accordingly, but
Since a line with increased crosstalk appears for each IH, the image quality deteriorates on the contrary. Therefore, the switching period was set to 2H.

As described above, according to this embodiment, by switching the input of the delay element using the controller, it is possible to relatively quickly correct the phase disturbance of the output signal when the input signal becomes discontinuous, and the tracking performance is improved. It is possible to realize a phase synchronization device with good performance.

Effects of the Invention As described above, according to the present invention, it is possible to improve the tracking performance of the phase synchronization device immediately after the input signal becomes discontinuous. Application of the present invention makes it possible to realize a synchronous demodulator with a relatively short pull-in time, which is extremely useful.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the principle of the signal processing device of the present invention, FIG. 2 is a block diagram of a reproduced chrominance signal demodulator which is an embodiment of the present invention, and FIG. 3 is a block diagram of a conventional reproduced chrominance signal demodulator. 4 is a schematic diagram showing the phase relationship between the input and output of a rectangular filter of a conventional reproduced color signal demodulator at the time of high-speed search, and FIG. It is a schematic diagram showing the phase relationship of the output. 1... Changeover switch, 2... Controller, 3... Input terminal, 4... Subtractor. ,
5... Delay means, 6... Output terminal, 7
... Phase shifter, 1) ... Signal processing device,
12...... changeover switch, 13......
2H counter, 14...Head amplifier switching pulse input terminal, 15...IH delay element, 16
...Subtractor, 17...180° phase shifter, 18...Frequency converter, 19...Voltage controlled oscillator, 20...・Phase comparator, 21...
...Crystal oscillator, 22...Low frequency conversion color signal input terminal, 23...Horizontal synchronization signal input terminal, 2
4...Output terminal, 31...Input terminal,
32... Voltage controlled oscillator, 33... Frequency converter, 34... IH delay element, 35...
...Subtractor, 36...Comb filter, 3
7... Output terminal, 38... Crystal oscillator, 39... Phase comparator.

Claims (7)

[Claims] (1) a delay means for delaying a signal by a predetermined time; a subtracter for subtracting the output signal of the delay means from the input signal; a phase shifter for shifting the phase of the output signal of the delay means by a predetermined amount; and an input of the delay means. A signal processing device comprising a switch for selecting the switch, and a controller for switching the switch. (2) The input signal is a video signal.
) The signal processing device described in item 2. (3) The input signal is a carrier color signal.
1) The signal processing device described in section 1). (4) The signal processing device according to claim (1), wherein the predetermined time is one horizontal scanning period. (5) Claim No. (1) that the predetermined amount is 180°
The signal processing device described in Section 1. (6) The signal processing device according to claim (1), wherein the controller switches the switch for two horizontal scanning periods. (7) The signal processing device according to claim (1), wherein the input signal is a carrier color signal during special reproduction.