JPH01162495A - Color signal processor - Google Patents

Abstract

PURPOSE:To prevent the fluctuation of hue, achromat and the like by adding the signal source output of which output polarity is inverted for each horizontal scanning period to a phase error difference signal output during the period of other than a vertical synchronizing pulse. CONSTITUTION:A gate pulse generated by a burst gate pulse generating circuit 25 constantly controls a burst gate circuit 8 and a phase comparator 9 is acted during a V pulse period. A switch circuit 27 is controlled to turn off during the V pulse period and a signal is not outputted to an adder 11 from a signal source 24 during the V pulse period. Consequently, the fluctuation of the phase error difference signal of the output of the phase comparator 9 after the V pulse is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a color (II) processing device that is effective for use in PAL color V'I'R and the like.

(Prior art) In color VTR etc., the luminance signal is generally F
M-modulated, the color signal is processed to convert the frequency to low frequency,
In addition, the reverse demodulation or frequency conversion operation is performed for recording or reproduction, the details of which are disclosed in, for example, Japanese Patent Laid-Open No. 129987/1983.

FIG. 2 is a block diagram of a conventional color signal processing device. For example, a reproduced output signal of a VTR is transmitted from input terminal 1 to LPF.
The color signal applied to a low-pass filter 2 and subjected to low frequency conversion is taken out, amplitude-controlled in an ACC (automatic gain control circuit) 3, and frequency-converted to a carrier color signal by a balanced modulator 4.

The output of the balanced modulator 4 is a BPF (band pass filter) 5
The unnecessary components generated by the balanced modulation are removed by the comb filter 6, and the crosstalk generated from adjacent recording tracks on the magnetic tape is removed by the comb filter 6, and the resulting signal is outputted to the output terminal 7 as a color signal.

On the other hand, a color burst (hereinafter simply referred to as burst) signal is taken out from the input terminal of the comb filter 6 and applied to the burst gate circuit 8, and its output is outputted from the reference oscillator 10 by the first phase comparator 9. compared to the signal. The phase error signal output is sent to the adder 11. Second LPF
12, the oscillation of a VCO (voltage controlled oscillator) 13 with a center frequency of approximately 320f□ (f□ is the horizontal scanning frequency) is controlled, and the oscillation frequency output is divided by 1/1 by a frequency divider 14.
The frequency is divided into 8 frequencies and four signals whose phases differ by 90 degrees are outputted to the selection circuit 15.

The selection circuit 15 selects one of the four input signals and applies it to the balanced modulator 16, where it is balanced modulated with the output signal of the reference oscillator 10, unnecessary components are removed by the BPF 17, and the first It is used as a carrier for the balanced modulator 4.

On the other hand, the luminance signal is generated by applying the reproduced signal applied from the input terminal 1 to the HP l',' (bypass filter) 18 to take out the l''M modulated signal, and transmitting it to the limiter 19. After limiting the amplitude, the FM demodulator 20
is extracted as a luminance signal.

The synchronization separation circuit 21 separates vertical and horizontal synchronization signals from the extracted luminance signal. Vertical synchronization (hereafter, ■
The pulse generation circuit 22 generates a pulse equivalent to the applied vertical synchronization signal, and also generates a horizontal synchronization signal (hereinafter referred to as H).
The pulse generating circuit 23 generates an H pulse synchronized with the horizontal synchronizing signal extracted in the same manner.

By the way, in the PAL system, the burst signal is input with a phase difference of 90 degrees every horizontal scanning period, so in a stable state, the cutting edge of the "A"-th position comparator 9 is +45 degrees and -45 degrees.
Phase error signals corresponding to each angle are generated in the order of 45 degrees. Therefore, the signal source 24 applies to the adder 11 a signal whose polarity is inverted every horizontal scanning period so as to cancel the phase error signal corresponding to ±45 degrees.

The Hearth I~Ge 1 pulse generation circuit 25 receives the 11 pulse signals from the H pulse generation circuit 23,
~A, generate a Verse 1 Hege-I-pulse with No. 1 timing, pass through the switch circuit 26, limit the operation of the Id source 242 phase comparator 9 and the Purst Gate 8 circuit 8, and Perth 1~))' -1-Limited to pulse period.

Note that the switch circuit 26 is connected to the pulse generating circuit 22.
The operation is controlled by the output of
The signal is then sent to the burst gate circuit 8, etc.

(Problems to be Solved by the Invention) However, the conventional color signal processing device described above has the following problems.

That is, during the pulse period, the control signal of the VCO 13 maintains a constant state, but this operation is incomplete due to the circuit configuration, and due to leakage current, the control voltage of co changes during the pulse period, and as a result, the VCO 13 After the pulse period, fluctuations in the phase error signal output from the phase comparator 9 become large, resulting in hue fluctuations accompanied by color fading in the upper portion of the television screen, resulting in an unsightly appearance.

As a countermeasure for this, in the field of NTSC TV, the switch circuit 26 is operated during the pulse period 1ift, which is effective. However, in the case of PAL TV signals, the polarity is reversed every horizontal scanning period. Since the signal is also applied during the V pulse period, there is a problem in that the above measures cannot be effective.

SUMMARY OF THE INVENTION In view of the problems of the conventional device described above, it is an object of the present invention to provide a PAL color signal processing device capable of suppressing the occurrence of color fading and two-hue fluctuations in the upper part of the screen.

(Means for Solving the Problems) The present invention has achieved the above-mentioned object by providing a switch circuit controlled by a vertical synchronizing pulse signal in a color signal processing device for a PAL color television signal. This is achieved by a configuration in which a signal source output whose output polarity is inverted every horizontal scanning period is added to the phase error signal output during the period other than that.

(Function) As described above, the present invention provides a switch circuit at the output of the signal source whose polarity is inverted every horizontal scanning period, and (1) does not conduct the above output during the pulse period; Since I made it conductive even during the burst gate pulse period,
(2) Fluctuations in the control voltage of the VCO during the pulse period are prevented, and therefore disturbances in hue at the top of the television screen are prevented as in the case of the NTSC television.

(Example) Hereinafter, the present invention will be explained in detail by way of an example using the drawings.

FIG. 1 shows a block diagram illustrating a color signal processing device according to an embodiment of the present invention. Reference numeral 27 is a switch circuit, and the other components are a switch circuit 26 (see FIG. ) is omitted, the configuration and operation are the same as in FIG. 2, and detailed explanation will be omitted.

In the present invention, with the configuration shown in FIG. 1, the gate pulse generated by the burst gate pulse generation circuit 25 constantly controls the burst gate 1 circuit 8, so that the phase comparator 9 operates even during the pulse period. . Further, the switch circuit 27 is controlled to be turned off during the pulse period.
Therefore, no signal is output from the signal source 24 to the adder 11 during the V pulse period.

As described above, in the present invention, the phase comparator 9 operates even during the pulse period, and the VCO 13 is no longer controlled by the output signal from the signal source 24 whose polarity differs every horizontal scanning period. (2) Fluctuations in the phase error signal output from the phase ratio unit 9 after the pulse are suppressed.

(Effects of the Invention) As is clear from the above explanation, the present invention has the following advantages: (1) By operating the phase comparator even during the pulse period, the control voltage of the VCO can be maintained at approximately a predetermined voltage without fluctuation; 1) It has the effect of preventing the change in hue or color fading at the top of the screen that occurs immediately after pulse generation in AL type televisions.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a color signal processing device according to an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional color signal processing device. 3... ACC (automatic gain control circuit), 4, 16, flat turret modulator, 6... comb filter, 8... burst game 1 circuit, 9... phase comparator, 10... reference Oscillator, 11... Adder, 13... VCO (voltage controlled oscillator), 14... Frequency divider, 15... Selection circuit,
19...Limiter, 20...FM demodulator, 21.
... Synchronization separation circuit, 22 ... Vertical synchronization pulse generation circuit, 23 ... Horizontal synchronization pulse generation circuit, 24 ... Signal source, 25 ... Burst gate pulse 27 ... Switch circuit. Patent applicant Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] A control loop is provided in which a variable frequency oscillator is controlled by a phase error signal obtained by comparing the phases of a color burst signal and an oscillation output of a reference oscillator at a subcarrier frequency, and a signal for frequency conversion of a carrier color signal is obtained. In a color signal processing device for a PAL color television signal, a switch circuit controlled by a vertical synchronization pulse signal is provided, and a signal source output whose output polarity is inverted every horizontal scanning period except for the vertical synchronization pulse period through this switch circuit. A color signal processing device characterized in that: is added to the phase error signal output.