JPS645513B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is used in a color television receiver capable of receiving both PAL and SECAM images.
This relates to a PAL/SECAM signal reproducing device.

Conventional configuration and its problems Figure 1 shows a conventional PAL/SECAM signal reproducing circuit. The configuration of the conventional example will be explained using FIG.

The operation of the circuit block will be explained when a SECAM-based composite video signal is input. A bell filter 4 extracts only the carrier color signal from the composite video signal. The SECAM carrier color signal that has passed through the bell filter 4 is FM-detected by the SECAM demodulator 5.
RY and BY color difference outputs are alternately obtained for each scanning line.

Next, the PAL modulator 6 uses the output from the PAL subcarrier oscillator 16 to modulate it into an analogous PAL signal. Hereinafter, this will be referred to as a simulated PAL signal.
In this case, the output is also R-Y, B-Y,
It is modulated alternately. Switch 7 at SECAM
falls to the terminal B side, so the pseudo PAL signal is
Guided by PAL bandpass filter 8, and further ACC
After being amplified by the amplifier 9, the output thereof is guided to a switch 11 on one side and a switch 12 on the other after being delayed by one scanning line time via a 1H delay line 10. Since the switches 11 and 12 are switched to the terminal B side during SECAM, the output of the ACC amplifier 9 and the output of the 1H delay line 10 are guided to the SECAM permutator 14. In this SECAM permutator 14, since the pseudo PAL signal output is alternately outputted with the RY and BY signals for each scanning line, the output of the ACC amplifier 9 and the output of the 1H delay line 10 are used. It serves to create continuous RY and BY signals. From SECAM permutator 14, continuous R-Y, B-Y
Signal is obtained, PAL RY demodulator 17, PAL
is guided to the B--Y demodulator 18, where the R--Y signal,
A demodulated output of the BY signal is obtained and output. In addition, the G-Y demodulated output is output from the G-Y matrix 19.
obtained by.

In addition, after the luminance signal passes through delay line 1,
Only the color subcarrier is attenuated by the color subcarrier trap 2, and further guided to the delay line 3, whose output becomes a luminance signal output.

Next, the operation of each circuit block when a PAL composite video signal is input will be explained.

The composite video signal that passed through the delay line 1 is
The chrominance signal is guided to the switch 7 as a path, and the luminance signal is led to the chrominance subcarrier trap 2 as a path. Now, since the switch 7 is turned to the terminal A side, the color signal is guided to the PAL band pass filter 8, and then to the ACC amplifier 9, and one of the outputs is from the switch 11 turned to the terminal A side. Therefore, the other one passes through the 1H delay line 10 and is led to the PAL matrix circuit 13 via the switch 12 that is folded down to the terminal A side. This PAL matrix circuit 1
3, the output of the ACC amplifier 9 and the output of the 1H delay line 10 create R-Y and BY signals, and the output of the PAL matrix circuit 13 is as follows.
RY signal goes to PAL RY demodulator 17, B-Y
The signal is guided to a PAL BY demodulator 18, and demodulated outputs of RY and BY are obtained, respectively. G again
-Y demodulation output is obtained from the GY matrix 19.

The output of the PAL matrix circuit 13 is led to a color synchronization circuit 15, where the transmission side color subcarrier and the subcarrier oscillator 16 are matched in phase.

After passing through the color carrier trap 2, the luminance signal passes through a delay line 3 and is output as a luminance signal output.

Now, in the conventional PAL/SECAM color signal reproducing circuit shown in Figure 1, delay line 1 and delay line 3
Two delay lines are used to delay the luminance signal. The reason for this is explained below. Third
The figure shows the delay time relationship of the SECAM signal in the conventional circuit. The SECAM color signal is delayed by a time T _s in order to pass through the bell filter 4. Furthermore, it takes time to pass through the PAL bandpass filter 8 as a pseudo PAL signal.
_T pdelay. Therefore, in order to match the delay times of the luminance signal and the color difference signal, the bell filter 4 inserts a delay line 1 corresponding to the delay time _Ts of the color signal into the luminance signal path. The delay time T _c of this delay line 1 is T _c = T _s (delay time at bell filter 4)
Choose as follows. Furthermore, a delay line 3 corresponding to the delay time T _p of the SECAM carrier color signal in the PAL bandpass filter 8 is inserted into the luminance signal path. The delay time T _d of this delay line 3 is T _d =
T _p (delay time at bandpass filter 8).

Figure 4 shows the delay time relationship of PAL signals in the conventional circuit. During PAL signal, PAL color signal is
It is delayed by a time T _p to pass through the PAL bandpass filter 8 . In order to match the delay times of the color signal and the luminance signal, a delay line 3 is inserted in the luminance signal path. This delay time T _d is T _d =T _p . At SECAM, the SECAM color signal passes through bell filter 4 and PAL bandpass filter 8, so delay line 1 and delay line 3 correspond to the delay time of these two filters.
is inserted into the luminance signal path. However, PAL
Since the chrominance signal passes only through the PAL bandpass filter 8 during signal processing, only the delay line 3 is required in the luminance signal path. From this, PAL
Sometimes the delay line 1 must delay both the chrominance signal and the luminance signal.

As shown above, the conventional PAL/SECAM shown in Figure 1
In the color signal reproducing circuit, two delay lines, the delay line 1 for delaying the composite video signal and the delay line 3 for delaying the luminance signal, must be used, which increases the number of components. Furthermore, since the delay line 1 requires a sufficiently wide band to delay both the chrominance signal and the luminance signal, it is disadvantageous in that it is expensive.

Purpose of the Invention The present invention eliminates the above-mentioned drawbacks, and provides a delay line with a small number of parts and low cost.
The purpose is to configure a SECAM color signal reproduction circuit.

Structure of the Invention The PAL/SECAM signal reproducing device according to the present invention includes:
A bell filter, SECAM
Pseudo from the output of the demodulator and PAL modulator
A PAL signal is obtained, and this pseudo PAL signal is processed using a trap, etc. that attenuates twice the harmonics of the PAL subcarrier.
At the PAL subcarrier frequency, it is supplied either through a filter that does not cause delay time or directly as one input signal of a selection switching means such as a selection switch.
A PAL composite video signal is first supplied to a PAL band pass filter to obtain a PAL carrier color signal from its output end, and this PAL carrier color signal is supplied as the other input signal of the selection switching means to the selection switching means. One of the signals is selected and extracted and supplied to the next processing circuit, while for the luminance signal, after attenuating the color subcarrier component of both the PAL or SECAM composite video signal using a color subcarrier trap, etc. The luminance signal is obtained from the output end of the luminance signal delay line through the luminance signal delay line, and the relationship between the delay times of the bell filter, the PAL bandpass filter, and the luminance signal delay line is set in consideration of the band characteristics of each filter. ,
Only one inexpensive delay line for luminance signals is required, reducing the number of parts and cost.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 2, 5, and 6. In FIG. 2, blocks having the same functions as those in FIG. 1 are given the same numbers and detailed explanations will be omitted.

The differences in Figure 2 from Figure 1 are as follows:
At the output end of the PAL modulator 6 that creates a pseudo PAL signal from the SECAM signal, there is a filter 20 such as a trap that has no delay time at the subcarrier frequency of the pseudo PAL signal and attenuates harmonics that are twice the PAL subcarrier frequency. is inserted, and the pseudo PAL signal is supplied to terminal B as one input of the changeover switch 12 through this filter 20, and on the other hand,
For PAL signals, directly from input terminal 1N,
The composite video signal is supplied to a PAL bandpass filter 8, and the PAL carrier color signal output from the PAL bandpass filter 8 is supplied to terminal A as the other input of the changeover switch 21. On the other hand, regarding the luminance signal, the composite video signal is first guided to a color subcarrier trap 2 to attenuate the color subcarrier component, and then guided to a delay line 3, from which a luminance signal output is obtained.

Next, the operation of the embodiment will be explained based on FIG. First, we will discuss the case where a SECAM composite video signal is input. The SECAM composite video signal is input to the bell filter 4, and after being converted into only the color signal,
FM is detected by SECAM demodulator 5 and R is detected for each scanning line.
-Y, BY color difference outputs are obtained alternately, and the color difference outputs are led to the PAL modulator 6 and modulated into a pseudo PAL signal using the output of the PAL subcarrier oscillator 16 to obtain a pseudo PAL output. After this, the pseudo PAL signal is
The subcarrier frequency of the pseudo PAL signal is guided to a filter 20, such as a trap, which attenuates harmonics twice the PAL subcarrier frequency without delay time. This filter 20 may be omitted in some cases. Pseudo PAL passed through filter 20
The signal is directed to switch 21 as one input. Since the switch 21 is switched to the terminal B during SECAM, the output of the filter 20 is connected to the ACC amplifier 9 via the switch 21.

Here, since both switches 11 and 12 fall to terminal B during SECAM, the output of ACC amplifier 9 is sent to SECAM permutator 14 via switch 11, and the output of ACC amplifier 9 is sent via 1H delay line 10 and switch 12 to SECAM. It is connected to the permutator 14. This SECAM permutator 14 uses pseudo
A continuous RY signal and a BY signal are created from the PAL signal using the output of the ACC amplifier 9 and the output of the 1H delay line 10, and the output is converted into a PAL signal.
The signal is led to the R--Y demodulator 17 and the PAL BY-- demodulator 18 to obtain R--Y and BY demodulated outputs. G-Y
A demodulated output is produced by a GY matrix 19.

On the other hand, the SECAM composite video signal is supplied to a chrominance subcarrier trap 2, which attenuates the chrominance subcarrier before being supplied to a delay line 3. If the time that the SECAM color signal is delayed by the bell filter 4 is T _s and the delay time of this delay line 3 is T _d , then
It is sufficient to set T _d = T _s . This situation is shown in FIG.

Next, the operation of each circuit block when a PAL composite video signal is input will be explained. The PAL composite video signal is input to the PAL bandpass filter 8,
Only the color signal is supplied to the switch 21.
During PAL, the switch 21 is turned to the terminal A side, so the output of the PAL bandpass filter 8 is
Connected to ACC amplifier 9. Switch 1 here
Both 1 and 12 fall to terminal A during PAL, so
The output of the ACC amplifier 9 is sent via the switch 11.
The output of the ACC amplifier 9 is connected to the PAL matrix 13 via a 1H delay line 10 and a switch 12. This PAL matrix 13 uses the output of the ACC amplifier 9 and the output of the 1H delay line 10 to
By subtracting both outputs, the RY signal is added to create the BY signal, respectively.
The outputs are sent to the PAL RY demodulator 17 and
Lead to PAL B-Y demodulator 18, R-Y, B-Y
Obtain the demodulated output. A G-Y demodulated output is produced by a G-Y matrix 19.

On the other hand, the PAL composite video signal is supplied to a color subcarrier trap 2, which attenuates the color subcarrier before being supplied to a delay line 3. PAL color signal
Time T _p delayed by PAL band pass filter 8,
If the delay time of this delay line 3 is T _d , then
It is sufficient to set T _d = T _p . This situation is shown in FIG.

From the above, in order to use only one delay line 3 for the luminance signal for both PAL and SECAM, the delay time T _s of the bell filter 4, the delay time T _p of the PAL bandpass filter 8, and the delay time T _d of the delay line 3 are required. The relationship between them should be approximately T _d = T _p = T _s .

Also, in general, bell filter 4 is better for PAL.
Since it has a narrower band than the bandpass filter 8, the delay time T _s in the bell filter 4 and the delay time T _p in the PAL bandpass filter 8 is T _p <
There is a relationship called T _s . Therefore, between T _d , T _p , and T _s ,
If we set the relationship T _p < T _d < T _s , the time difference between the color signal output and the luminance signal output on the screen will be equal to PAL.
In both SECAM systems, it can be made inconspicuous, and only one delay line is required in the luminance signal path.

In addition, in Fig. 2, the output of PAL modulator 6 is PAL
Although it does not pass through the bandpass filter 8, there is no practical problem because the output of the PAL modulator 6 is only the carrier color signal.

Effects of the Invention As described above, according to the present invention, the conventional
While the PAL/SECAM color signal reproducing circuit uses two delay lines, a wideband delay line that delays the composite video signal and a luminance signal delay line, the PAL/SECAM color signal reproducing circuit of the present invention uses It is possible to use one inexpensive delay line for brightness signals, which is effective in reducing the number of parts and cost.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional PAL/SECAM color signal reproducing circuit, and FIG. 2 is a block diagram of a PAL/SECAM signal reproducing apparatus according to an embodiment of the present invention.
Figure 3 is a diagram showing the delay time relationship of SECAM signals in the conventional circuit, Figure 4 is a diagram showing the delay time relationship of PAL signals in the conventional circuit, and Figure 5 is a diagram showing the delay time relationship of the SECAM signal in the conventional circuit.
FIG. 6 is a diagram showing the delay time relationship of SECAM signals, and FIG. 6 is a diagram showing the delay time relationship of PAL signals in the present invention. 2...Color subcarrier trap, 3...Delay line, 4...Bell filter, 5...SECAM demodulator, 6...PAL modulator, 8...PAL bandpass filter, 20...Filter, 21...Selection switching means.

Claims (1)

[Claims] 1. An input terminal that receives a composite color television signal as input, and a bell filter that is connected to this input terminal and inserted at the transmitting side of the SECAM signal transmission system, and that has characteristics opposite to those of a bell filter that attenuates the carrier color signal. and a first filter means for extracting a carrier color signal from the composite color television signal when the composite color television signal is of SECAM format; and a SECAM connected to the output end of the first filter means for FM demodulating the carrier color signal. a demodulating means, a converting or modulating means for converting or modulating the output signal of the SECAM demodulating means into a PAL system or a signal equivalent thereto, and removing harmonic components contained in the output signal of the converting or modulating means as necessary. a second filter means; a selection switching means for inputting the output signal of the conversion or modulation means or the output signal of the second filter means as a first input signal; connected to the composite color television signal input terminal; a delay means for delaying the luminance signal by a time T _d and outputting the luminance signal; and a third filter means connected to the composite color television signal input terminal for extracting the carrier color signal, the third filter means The output signal is supplied as a second input signal to the selection switching means, and either the first input signal or the second input signal is selectively outputted to the output of the selection switching means.
PAL/SECAM signal reproducing device. 2. PAL/SECAM according to claim 1, characterized in that the delay time T _d of the delay means is set approximately equal to the delay time T _p of the third filter means.
Signal regenerator. 3. A patent claim characterized in that the delay time T _d of the delay means is set to satisfy T _p < T _d < _{T s with respect to the delay time T s of} the first filter means and the delay time T p of the third filter means. The PAL/SECAM signal reproducing device according to item 1.