JPH02260784A - Chrominance signal processing circuit - Google Patents

Abstract

PURPOSE:To generate a required signal phase shift stably and more accurately independently of an input frequency by selecting the outputs of plural phase shift circuits and applying the output to a hue adjusting circuit. CONSTITUTION:A phase shifter A 1a selects a cut-off frequency decided by the constant of R1 38, R2 39, C1 40 and C2 41 to be 3.58MHz and a phase shifter B 1b selects a cut-off frequency decided by the constant of R1 38, R2 39, C1 40 and C2 41 to be 4.43MHz. Thus, continuous wave signals 11a, 12a being the outputs of the phase shifter A 1a are generated into signals phase-shifting to a 3.58MHz input signal by +45 deg. and -45 deg.. Moreover, continuous wave signals 11b, 12b being the outputs of the phase shifter B 1b are generated into signals phase-shifting to a 4.43MHz input signal by +45 deg. and -45 deg.. Switches 4a, 4b in interlocking with each other lead the output of the phase shifter A 1a to a hue adjusting device 2 when they are turned to the position 1 and lead the output of the phase shifter B 1b to the hue adjusting device 2 when they are turned to the position 2. Thus, required signal phase shift is applied independently of the frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color signal processing circuit used in television receivers and the like.

[Conventional technology]

Currently, the world's color television signal system is NTS.
There are three systems: C, PAL, and SECAM. For this reason, color television receivers that are compatible with multiple formats are manufactured, and the integrated circuits installed in these sets are also manufactured as systems that can support multiple formats. The frequency of the color subcarrier in the NTSC system is 3
．． There are 58MH2 and 4.43MH2, and the phase shift circuit used in the color signal processing circuit of the multi-system color television integrated circuit is approximately 4MH2, which is the middle of the above two frequencies.
They used z as the standard and planned for common use.

Figures 2 to 5 relate to conventional color signal processing circuits used in television receivers, etc. Figure 2 is a block diagram showing a phase shift circuit system for color signal processing, and Figure 3 is a block diagram showing a phase shift circuit system for color signal processing.
4 is a circuit diagram of a phase shifter, FIG. 4 is a circuit diagram of a hue adjuster, and FIG. 5 is a graph showing the relationship between phase and color subcarrier frequency. In the figure, (1) is a phase shifter, (2) is a hue adjuster, (3) is a color demodulator, and (5) is an input of a continuous wave signal that is locked to the burst signal and has a certain phase angle with the burst signal. terminals, (6) is the hue adjustment terminal that adjusts the hue by externally applied voltage, (7) is the color signal, (8) e (9) and 00 are the color demodulation output terminals, αυ, @ is the phase shifter (1) Generated continuous wave signals with a phase difference of 90° from each other, □□
□ and 0→ are continuous wave signals arbitrarily adjusted by the hue adjuster (2), respectively.

Next, the operation will be explained.0 In Fig. 2, the signal ' that is locked to the burst signal and input from the input terminal (5) of the continuous wave signal that has a certain phase angle with the burst signal is passed through the phase shifter (1). Generate two signals with different phase differences.

In FIG. 3, two continuous wave signals aυ and σ are output. Normally, the capacitance ftcs■ and the capacitance C20υ are the same value, and the resistance R
s@ and resistance R2 (to) are also set to the same value. In addition, these OCR time constants are constants that become the cutoff frequency of the input signal, and the continuous wave signal αη is a signal whose phase is shifted by +45 degrees from the input signal, and the continuous wave signal @ is a signal whose phase is shifted by 45 degrees from the input signal. It's a signal. The two signals having a phase difference of 906 in this manner are input to the hue adjuster (2) shown in FIG.

The hue adjuster (2) has a hue adjustment terminal (6) that performs hue adjustment using an externally applied voltage, and this terminal voltage adjusts the relative phase angle of 90°, which is the relative phase angle of the two input continuous wave signals αυ and a2. While maintaining the absolute phase angle, the continuous wave signals a, 1. Output α→.

The continuous wave signal Q3-←→ output from the hue adjuster (2) having the configuration shown in FIG.
), and the color signal (power and this continuous wave signal α) is output in the subsequent color demodulator (3).
, a4, and color demodulation output terminal (8) ~
QO2 is configured to demodulate R-Y, G-Y, B-Y color difference M codes respectively.

[Problem to be solved by the invention]

Since the conventional color signal processing circuit is configured as described above, it is possible to transfer the color signal processing circuit used in the color signal processing circuit of a multi-system color television receiver that handles two color subcarrier frequencies of 3.58 MHz and 4.43 MHz. As mentioned above, the phase circuit constant is determined by setting the cutoff frequency to approximately 4MHz, which is the middle of these two frequencies, so it is 3.58MHz.
z and 4.43 MHz cannot be generated accurately.

The relationship between the phase and the color subcarrier frequency when the cutoff frequency is set to 4.00 MHz is as shown in FIG.

As shown in the figure, when the hue normal is 1, a deviation of about 6° occurs between 3.58 MHz and 4.43 MH2. Also, the hue change range is approximately 96° for one color subcarrier and approximately 8° for the other color subcarrier.
4° unbalanced tonal. The new one is 3.58MH2 and 4
．． There were problems such as the opposite change at 43 MHz.

The present invention was made to solve the above-mentioned problems, and aims to stably and more accurately generate a necessary signal phase regardless of the input frequency.

[Means to solve the problem]

The color signal processing circuit according to the present invention includes phase shift circuits for each of a plurality of color subcarrier frequencies handled in a multi-system color television receiver.

[Effect]

The color signal processing circuit according to the present invention is provided for a plurality of color subcarrier frequencies, and each phase shift circuit selects the outputs thereof by a switch circuit, and the necessary signal phase is input to the hue adjustment circuit input regardless of the frequency. can be supplied.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a block diagram showing the configuration of the color signal processing circuit. Figure Nioite, (2), (3), (5)-C1O,
Q3. (14) C Since this is the same as that shown in the conventional example of FIG. 2, the explanation will be omitted. (1a) is the phase shifter A, (1
b) is phase shifter B, (4a) t (4b) is a switch that operates in conjunction, (lla) and (12a) are +45° and -45° for a 3.58 MHz input signal generated by phase shifter A. ° Phase-shifted continuous wave signal, (Bb), Q2b)
is + for the 4.43MHz input signal generated by phase shifter B.
Continuous wave signals phase shifted by 45° and −45°.

Next, I will explain the operation. Phase shifter A (la) and phase shifter B (Qb) have the same configuration as shown in FIG. 3 used to explain the conventional example, but phase shifter A (la) ) - Rt - Ct) and the cutoff frequency determined by the constant of C7 (6) is set to 3.58 MH2. Similarly, the phase shifter B (lb) is also R as shown in FIG.
1(c) - The cutoff frequency determined by the constants of Rt'N, Ct and C1 is set to 4.43MHz.

As a result, the continuous wave signals C11a) and (1za), which are the outputs of the phase shifter A(la), generate signals whose phases are shifted by +45° and -45° with respect to the 3.58 MHz input signal.

Also, the continuous wave signal (ll
b) and (12b) are + for a 4.43MHz input signal.
45° and -45° phase shifted signals are generated. Switches (4a) and (4b) that operate in conjunction lead the output of phase shifter A (la) to the hue adjuster (2) when switched to the side.
When switched to the side, the phase shifter BQb) output is changed to the hue adjuster (
2). The configuration after the hue adjuster (2) is the same as that of the conventional example.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to eliminate the deviation in normal 1 of the hue adjustment volume caused by the difference in color subcarrier frequencies in a color television receiver that can be used for multiple systems, and the relative difference between two color subcarriers due to hue adjustment. This has the effect of suppressing the phase angle shift as much as possible, and has the effect of improving the quality of multi-system television receivers, which will require increasingly higher performance in the future.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a color signal processing circuit according to an embodiment of the present invention, Figs. 2 to 5 relate to conventional color signal processing circuits, and Fig. 2 shows a phase shift circuit system for color signal processing. FIG. 3 is a circuit diagram of a phase shifter, FIG. 4 is a circuit diagram of a hue adjuster, and FIG. 5 is a graph showing the relationship between phase and color subcarrier frequency. In the figure (1a
) is phase shifter A, (1b) is phase shifter B, (2) is hue adjuster, (3) is color demodulator, (4a) and (4b) are switches, (5) is input terminal, ( 6) is a hue adjustment terminal, (7) is a color signal, (s) # (9) #αQ is a color demodulation output terminal, (lla), (llb), (12a), (12b)
, (L'l and α) are continuous wave signals. In the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] In the color signal processing device of a multi-system television receiver,
A phase shift circuit consisting of a plurality of circuits that locks to an input burst signal and receives as input a color subcarrier signal having a certain phase angle with respect to the burst signal, and an output of the phase shift circuit consisting of a plurality of circuits that has a different input burst signal frequency. A color signal processing circuit comprising: a switch circuit that selects a signal from a plurality of phase shift circuits; and a hue adjustment circuit that receives the output of the switch circuit as an input; .