JPH0445345Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field]

The present invention relates to a comb filter for separating a luminance signal component and a carrier color signal component from a color composite video signal in the NTSC system.

[Prior art]

The basic configuration of a conventional comb filter is as follows:
The one shown in FIG. 1 is known. Here, a color composite video signal is input from input terminal 1,
A luminance signal and a carrier color signal are separately outputted from output ends 2 and 3, respectively. And IH
The delay element 4 delays the original signal by IH, and this is added to the original signal via the adder 5 to obtain a luminance signal. Also, it is subtracted from the original signal via the subtracter 6 to obtain a carrier color signal. You get it.

[Technical issues]

The problem here is that the IH delay element used has poor spurious characteristics, so the color signal leaks into the burst signal in the separated carrier color signal.
Depending on the signal content, the phase of the burst signal may change, making it impossible to perform faithful color demodulation.
Conversely, the burst signal leaks into the scanning period, causing colored lines to appear on the screen even when a white signal is received.

[Purpose of invention]

The present invention was developed based on the above circumstances, and the burst signal is extracted before the IH delay element.
The present invention aims to provide a comb-shaped filter that can be inserted thereafter to achieve faithful color reproduction.

[Technical configuration of the idea]

For this purpose, the present invention uses an IH delay element to separate a color composite video signal into a luminance signal and a color signal, and a bypass connecting the input side of the color composite video signal and the color signal output side is provided. and a switching circuit for switching the input of the color composite video signal to bypass, and the switching circuit is configured to switch so that the burst flows to the bypass side during the scanning period. It is.

【Example】

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 2 and 3. In FIG. 2, reference numeral 11 is an input terminal;
As before, an IH delay element 14, an adder 15, and a subtracter 16 are connected between the two output terminals 12 and 13.
is located. Here, in particular, there is a sampling switching circuit 17 between the input terminal 11 and the filter circuit, which switches to a bypass 21 for the filter circuit (consisting of an IH delay element 14, an adder 15, and a subtracter 16). It is set to be connected. Further, the bypass 21 is connected to the output terminal 13 via an insertion switching circuit 18. These switching circuits 17 and 18 are switched so that the original signal flows to the bypass 21 side by a gate pulse 19 of a burst gate (not shown). In such a configuration, burst gate pulse 1
9, during the burst period when the switching circuits 17 and 18 are switched, the color composite video signal bypasses the filter circuit, is sent to the output terminal 3 via the bypass 21, and becomes the burst signal. There is no leakage of color signals, and no leakage of burst signals during the scanning period. Then, during periods other than the burst signal, the switching circuits 17 and 18 are switched to the normal filter circuit side,
It will function as a comb filter. In the above embodiment, a case has been described in which the burst signal bypasses only the IH delay element 14, but it is not necessary to bypass only the delay element. For example, as shown in FIG. A bypass 21 can also be connected to the output side of the chroma bandpass 20 so that the burst signal does not pass through the bandpass 20. This is because if the burst signal is passed through a band pass, it will become sluggish, which will affect the ACC and APC of the chroma circuit. Therefore, it is effective not to allow the burst signal to pass through the chroma band pass 20.

[Effect of the idea]

The present invention, as detailed above, provides a bypass and uses a switching circuit to avoid passing the signal to the IH delay element during the period of the burst signal. Leakage into the period and leakage into the burst of the carrier color signal can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional example, FIG. 2 is a circuit diagram showing one embodiment of the present invention, and FIG. 3 is a circuit diagram of another embodiment. 11...Input terminal, 12,13...Output terminal,
14... IH delay element, 15... Adder, 16...
...Subtractor, 17, 18...Switching circuit, 19...Burst gate pulse, 20...Chroma band pass, 21...Bypass.

Claims (1)

[Scope of utility model registration request] A device that separates a color composite video signal into a luminance signal and a color signal using an IH delay element, comprising a bypass connecting the input side of the color composite video signal and the color signal output side, and the color composite video signal 1. A comb filter, comprising: a switching circuit for switching an input to a bypass, the switching circuit being configured to switch so that bursts flow to the bypass side during a scanning period.