JPH01117590A - Picture quality improving circuit for television receiver - Google Patents

Abstract

PURPOSE:To reduce high-frequency noise components and color noise by inserting a trap whose center frequency is nearly 5MHz to an output terminal of video detection. CONSTITUTION:A trap 5 whose center frequency is nearly 5MHz comprising an inductor L1 and a capacitor C1 is inserted to the detection output terminal of a video detection circuit 1. The frequency characteristics of the trap 5 and the frequency characteristics of the video detection circuit 1 are as shown in figures. In the NTSC system, the signal component is subjected to band limit at nearly 4.2MHz and the noise band generated in the color television receiver is wider. The trap 5 whose center frequency is nearly 5MHz is inserted to the detection output line to prevent the noise of higher frequency than the signal component from entering a color demodulation circuit 4 and the frequency characteristics at the high frequency band in the color demodulation circuit 4 is brought into the frequency characteristics (b) after the insertion of trap from a conventional frequency characteristic (a) to reduce color noise.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image quality improvement circuit for a color television receiver.

2. Description of the Related Art In recent years, color television receivers have become larger and their image quality has improved markedly. In the color signal system, attempts have been made to improve color reproducibility and color transients by widening the band of the color signal demodulation circuit, but this has had the disadvantage of increasing color noise and cross color.

FIG. 4 shows the circuit configuration of a conventional color television receiver. The detection output from the video detection circuit 1 passes through an input switching circuit 2 that switches signals with the video input, and is separated into a luminance signal and a color signal by a comb-shaped filter 3, and the color signal is demodulated by a color demodulation circuit 4. be done.

Problems to be Solved by the Invention In the above configuration, the color noise generated in the color demodulation circuit 4 may deteriorate the image quality, and in particular, as the color demodulation circuit 4 becomes wider, the color noise becomes more noticeable. , this improvement was desired.

In view of the above problems, the present invention provides an image quality improvement circuit for a color television receiver that can reduce color noise.

Means for Solving the Problem To achieve this object, the image quality improvement circuit for a color television receiver of the present invention has a trap with a center frequency of about 5 MHz inserted at the detection output end of a video detection circuit.

Function: The image quality improvement circuit of the present invention reduces the high-frequency noise components of the signal entering the color signal demodulation circuit by inserting a trap with a center frequency of about 5 MHz at the detection output end of the video detection circuit. This reduces noise.

Embodiment An image quality improvement circuit for a television receiver according to an embodiment of the present invention will be described below. FIG. 1 is a block diagram of an image quality improvement circuit according to the present invention. An inductor L1 is connected to the detection output terminal of the video detection circuit 1. Center frequency approximately 5M due to capacitor C1
Insert the Hz trap 6. FIG. 2 is a frequency characteristic diagram of this trap 6. FIG. 3 shows the frequency characteristics of the video detection circuit 1. In the NTSC system, the signal components are approximately 4
．． Although the band is limited by 2MH, the band of noise generated in a color television receiver is wider. By inserting a trap 6 with a center frequency of approximately 5MK into the detection output line, noise in a higher frequency range than the signal component is prevented from entering the color demodulation circuit 4, and the high frequency noise within the band of the color demodulation circuit 4 is prevented from entering the color demodulation circuit 4. By changing the frequency characteristic of the part from the conventional frequency characteristic a shown in Fig. 3 to the frequency characteristic after trap insertion,
Color noise can be reduced. Note that although the trap is configured with an inductor and a capacitor, other traps may be used.

Effects of the Invention As described above, according to the present invention, by inserting a trap with a center frequency of about 5M1-1z at the video detection output end, high frequency noise components can be reduced and cuff noise can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an image quality improvement circuit in an embodiment of the present invention, FIG. 2 is a frequency characteristic diagram of a trap,
FIG. 3 is a frequency characteristic diagram of the detection output, and FIG. 4 is a configuration diagram of a conventional image quality improvement circuit. 1...Video detection circuit, 5...Trap.

Claims (1)

[Claims] A color television receiver that separates a composite video signal into a luminance signal and a color signal using a comb-shaped filter and performs signal processing, characterized in that a trap with a center frequency of about 5 MHz is inserted in the video detection output line. Image quality improvement circuit for television receivers.