KR100771789B1 - Television receiver with video signal distortion compensation - Google Patents

Abstract

According to the present invention, in a TV set such as a TV set or a VTR, a demodulation unit can correct distortion of an analog video signal, and can also change a distortion correction frequency band, thereby improving video quality and improving video quality. It is an object of the present invention to provide a TV receiver having a signal distortion correction function.

A TV receiver having a video signal distortion correction function according to the present invention includes: an IF circuit unit 210 for demodulating an IF signal to restore an audio signal and a video signal; A distortion correction circuit 220 for removing a distortion frequency included in the video signal input from the IF circuit 210; And a video buffer 230 for outputting a video signal from the distortion correction circuit unit 220.

 Video signal, distortion correction, demodulator, IF signal, TV receiver

Description

TV receiver with video signal distortion correction {TELEVISION RECEIVER WITH VIDEO SIGNAL DISTORTION COMPENSATION}

1 is a block diagram of a conventional TV receiver.

2A, 2B, and 2C are waveform diagrams of video signals output from the demodulator of FIG.

3 is a block diagram of a TV receiver according to the present invention;

4 is a graph of trap characteristics by the distortion correction circuit unit of FIG. 3.

FIG. 5 is a graph illustrating insertion loss characteristics of the distortion correction circuit unit of FIG. 3. FIG.

6A, 6B, and 6C are waveform diagrams of video signals output from the demodulator of FIG.

Explanation of symbols on the main parts of the drawings

100: RF circuit part 200: demodulation part

210: IF circuit portion 220: distortion correction circuit portion

230: Video buffer L1: first inductor

C1: first capacitor C2: second capacitor

R1: first resistor R2, R3: second, third resistor

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TV receiver such as a TV set or a VTR. In particular, a demodulator can correct distortion of an analog video signal, and can also change a distortion correction frequency band, thereby improving image quality by improving video characteristics. The present invention relates to a TV receiver having a video signal distortion correction function.

In general, a TV receiver applied to a TV set or VTR is configured as shown in FIG.

1 is a block diagram of a conventional TV receiver.

1 illustrates a conventional TV receiver including a demodulation unit 20 including an RF circuit unit 10 for converting an input RF signal into an IF signal and an IF circuit unit 21 for demodulating the IF signal from the RF circuit unit 10. ).

Here, the video buffer 22 is added to the output terminal of the demodulator 20 to block the influence of the interference signal from the outside. Since the video buffer 22 separates the internal and external parts of the demodulator 20 from the interference signal, the video buffer 22 can be used to improve the distortion of the video signal by blocking an external influence on the video signal. Can be.

However, even when the video buffer is used in the conventional TV receiver, the video signal output from the demodulator of the conventional TV receiver is distorted under the influence of the system while passing through the RF circuit and the demodulator. This will be described with reference to (a), (b) and (c) of FIG. 2.

Referring to the waveforms of the video signals shown in FIGS. 2A, 2B, and 2C, the video signals illustrated in FIG. 2A include overshoots (OS) and undershoots (US: UnderShoot). Distortion), and a distortion phenomenon such as asymmetric ringing (R: ringing) is generated in the video signal of the dot cross pattern shown in FIG. 2 (b). Distortion (D) is also generated in the video signal of the pulse pattern shown in FIG.

As described above, the video signal output from the demodulation unit of the conventional TV receiver is distorted under the influence of the system while passing through the RF circuit unit and the demodulator (Demodulator), thereby degrading the TV quality.

The present invention has been proposed to solve the above problems, the object of which is to correct the distortion of the analog video signal in the demodulator in a TV receiver such as a TV set or VTR, and also can change the distortion correction frequency band Accordingly, an object of the present invention is to provide a TV receiver having a video signal distortion correction function capable of improving image quality by improving video characteristics.

In order to achieve the above object of the present invention, a TV receiver having a video signal distortion correction function of the present invention comprises: an IF circuit section for demodulating an IF signal to restore an audio signal and a video signal; A distortion correction circuit unit which removes a distortion frequency included in the video signal input from the IF circuit unit; And a video buffer for outputting a video signal from the distortion correction circuit unit.

The TV receiver may further include an RF circuit unit for converting an input RF signal into an IF signal and outputting the IF signal to the IF circuit unit.

The distortion correction circuit unit is characterized in that the LC trap circuit is set to the same trap frequency as the distortion frequency of the video signal.

The distortion correction circuit unit includes an LC trap circuit in which a first inductor and a first capacitor are connected in series from the output line of the IF circuit unit to a ground, and a trap frequency of the first inductor and the first capacitor is connected to the video signal. Characterized in that the same setting as the included distortion frequency.

The distortion correction circuit unit may further include a second capacitor connected in parallel to the first inductor to change trap selectivity of the first inductor and the first capacitor.

The distortion correction circuit unit may further include a first resistor connected between the output line of the IF circuit unit and the first inductor to improve insertion loss.

The distortion correction circuit unit may include at least one of the first inductor, the first capacitor, and the second capacitor as a variable element, so as to vary the trap frequency in response to the selected TV broadcast.

The distortion correction circuit section, in front of the LC trap circuit, reduces the level of the video signal from the IF circuit section, a second resistor connected between the output terminal of the IF circuit section and ground for voltage division, and the output terminal of the IF circuit section. And a third resistor connected between the first resistor and the first resistor.

The IF circuit section, the distortion correction circuit section and the video buffer are formed in one demodulation IC.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings referred to in the present invention, components having substantially the same configuration and function will use the same reference numerals.

3 is a block diagram of a TV receiver according to the present invention.

Referring to FIG. 3, the TV receiver according to the present invention includes an RF circuit unit 100 for converting an input RF signal into an IF signal and outputting the IF signal to the IF circuit unit 210, and an IF signal from the RF circuit unit 100. Demodulating unit 200 to provide a video signal and an audio signal. Here, the RF circuit unit 100 and the demodulation unit 200 may be implemented with each IC.

The demodulator 200 includes an IF circuit unit 210 for demodulating an IF signal input from the RF circuit unit 100 to restore an audio signal and a video signal, and a video signal input from the IF circuit unit 210. A distortion correction circuit 220 for removing the distortion frequency, and a video buffer 230 for outputting a video signal from the distortion correction circuit 220.

The distortion correction circuit 220 includes an LC trap circuit configured to set a trap frequency equal to the distortion frequency of the video signal. Referring to a specific circuit implementation example, the LC trap circuit includes an output line of the IF circuit unit 210. The first inductor L1 and the first capacitor C1 are connected in series to ground at. At this time, the trap frequency by the first inductor L1 and the first capacitor C1 is set to be equal to the distortion frequency included in the video signal.

4 is a graph of trap characteristics by the distortion correction circuit unit of FIG. 3.

3 and 4, the distortion correction circuit 220 is connected to the first inductor L1 in parallel to determine trap selectivity of the first inductor L1 and the first capacitor C1. The second capacitor C2 may be changed. In this case, as illustrated in FIG. 4, the trap selectivity may be changed (T1 → T2) so as not to affect the video signal of the base band.

5 is a graph illustrating insertion loss characteristics of the distortion correction circuit unit of FIG. 3.

3 and 5, the first resistor R1 may further include a first resistor R1 connected between the output line of the IF circuit unit 210 and the first inductor L1 to improve insertion loss.

In this case, as illustrated in FIG. 5, a trap graph with improved insertion loss is shown as compared with the trap graphs of the first inductor L1 and the first capacitor C1.

In addition, the distortion correction circuit 220 may include at least one of the first inductor, the first capacitor, and the second capacitor as a variable element so as to correspond to each TV broadcasting method such as an NTSC method or a PAL method. In this case, the trap frequency may be changed corresponding to the selected TV broadcast.

In addition, the distortion correction circuit unit 220, in front of the LC trap circuit, reduces the level of the video signal from the IF circuit unit 210, and a second connected between the output terminal of the IF circuit unit and ground for voltage division. The resistor R2 further includes a third resistor R3 coupled between the output terminal of the IF circuit unit and the first resistor.

In order to reduce the size and simplify the manufacturing process, the IF circuit 210, the distortion correction circuit 220, and the video buffer 230 are preferably formed in one demodulation IC.

6A, 6B, and 6C are waveform diagrams of video signals output from the demodulator of FIG. 3.

FIG. 6A is a composite video signal including a video signal, FIG. 6B is a video signal having a dot cross pattern, and FIG. 6C is a video signal having a pulse pattern.

Hereinafter, the operation and effects of the present invention will be described in detail with reference to the accompanying drawings.

The TV receiver of the present invention is implemented to improve image quality by removing distortion frequencies of video signals generated through the RF circuit unit and the IF circuit unit, which will be described with reference to FIGS. 3 and 6.

First, referring to FIG. 3, the RF circuit unit 100 of the TV receiver of the present invention converts an input RF signal into an IF signal and outputs it to the IF circuit unit 210, which is approximately 50 MHz to 860 MHz in frequency band. The frequency band corresponding to the selected channel of the TV RF signal is converted into an IF signal. The IF signal is, for example, 45.75 MHz in the NTSC TV system and 38.9 MHz in the PAL TV system.

Next, the demodulation unit 200 of the present invention demodulates the IF signal from the RF circuit unit 100 to restore and output a baseband video signal and an audio signal. In this process, the distortion frequency included in the video signal is output. To improve the TV picture quality.

On the other hand, when the distortion of the video signal is briefly described, the distortion frequency included in the video signal has been identified as a frequency higher than the frequency of the video signal of the baseband. Accordingly, removing the distortion frequency may improve the distortion of the video signal. I found out.

In view of this, the IF circuit unit 210 of the demodulator 200 demodulates the IF signal to restore the audio signal and the video signal, and outputs the video signal to the distortion correction circuit unit 220. The distortion correction circuit 220 removes the distortion frequency included in the video signal input from the IF circuit unit 210, and outputs the video signal from which the distortion frequency is removed through the video buffer 230. Here, the IF circuit unit 210, the distortion correction circuit unit 220, and the video buffer 230 are formed in one demodulation IC.

Hereinafter, the distortion correction circuit 220 will be described in detail.

Referring to FIG. 3, the distortion correction circuit unit 220 includes an LC trap circuit, which sets a trap frequency equal to the distortion frequency of the video signal, that is, the LC trap circuit is the IF circuit unit. The first inductor L1 and the first capacitor C1 are connected in series from the output line of 210 to ground, and the trap frequency by the first inductor L1 and the first capacitor C1 is adjusted. The distortion frequency included in the video signal is trapped by setting the same distortion frequency included in the video signal. For example, the trap frequency is set higher than 4.43 MHz, which is an image (eg, chroma) frequency in the PAL scheme, and set higher than 3.58 MHz, which is an image (eg, chroma) frequency, in the NTSC scheme. Set the trap frequency higher than the video signal of each system.

3 and 4, in the distortion correction circuit unit 220, a second capacitor C2 is connected in parallel to the first inductor L1, so that the first inductor L1 and the first capacitor ( The trap graph T1 determined by C1) may be changed to the trap graph T2 by the second capacitor C2. When the trap selectivity is changed in this way, the level of the video signal may be reduced. .

That is, if the attenuation degree of the trap frequency by the first inductor L1 and the first capacitor C1 is too deep, the adjacent video signal may be attenuated, thereby reducing the trap attenuation somewhat. Accordingly, since the distortion frequency is reduced, the level of the video signal is not attenuated, so that only the distortion frequency component can be removed.

3 and 5, the distortion correction circuit unit 220 is connected between an output line of the IF circuit unit 210 and the first inductor L1 to improve an insertion loss. In addition, when a trap is formed at the distortion frequency by the first inductor L1 and the first capacitor C1, the insertion loss of the frequency band of the video signal is improved.

Meanwhile, when at least one of the first inductor, the first capacitor, and the second capacitor of the distortion correction circuit unit 220 is implemented as a variable element, the trap frequency may be changed in response to the selected TV broadcast. The trap frequency can be set corresponding to the NTSC method and the PAL method, respectively.

The level of the video signal from the IF circuit unit 210 may be reduced through the second and third resistors R2 and R3 for voltage division of the distortion correction circuit unit 220. This is because many IC products output a baseband video signal with an IF circuit section of 2Vpp, while a circuit IC products processing a baseband video signal of 1Vpp can be used at the rear of the demodulator, so it outputs a baseband video signal of 2Vpp. In the case of using the IF circuit section, it is possible to cope with a case where a baseband video signal of 1 Vpp is required at the rear stage.

In the present invention as described above, referring to FIGS. 6A, 6B, and 6C, a distortion correction circuit is added between the IF circuit unit and the video buffer as compared with the conventional video signal shown in FIG. 2. Therefore, the distortion of the analog video signal is improved, and the trap constant is changed to be applicable to the PAL (Chroma = 4.43 MHz) and NTSC (Chroma = 3.58 MHz) systems. In addition, the peaking and damping constants may be changed through the first resistor and the second capacitor to adjust the level of chroma components included in the image signal. Accordingly, the overshoot and undershoot characteristics of the video signal are improved, the ringing characteristics are improved, and the pulse pattern characteristics are improved.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, but is defined by the claims, and the apparatus of the present invention may be substituted, modified, and modified in various ways without departing from the spirit of the present invention. It is apparent to those skilled in the art that modifications are possible.

According to the present invention as described above, the present invention relates to a TV receiver such as a TV set or a VTR. In particular, the demodulator can correct distortion of an analog video signal, and can also change the distortion correction frequency band, thereby improving video characteristics. There is an effect that can improve the image quality by improving.

Claims (9)

An IF circuit unit for demodulating the IF signal to restore the audio signal and the video signal; A distortion correction circuit unit which removes a distortion frequency included in the video signal input from the IF circuit unit; And A video buffer for outputting a video signal from the distortion correction circuit section TV receiver having a video signal distortion correction function comprising a. The method of claim 1, wherein the TV receiver, RF circuit unit for converting an input RF signal into an IF signal and outputting to the IF circuit unit TV receiver having a video signal distortion correction function further comprising. The method of claim 1, wherein the distortion correction circuit unit And an LC trap circuit configured to set a trap frequency equal to the distortion frequency of the video signal. The method of claim 1, wherein the distortion correction circuit unit An LC trap circuit connected in series with a first inductor and a first capacitor from the output line of the IF circuit part to ground; And a trap frequency set by the first inductor and the first capacitor to be equal to the distortion frequency included in the video signal. The method of claim 4, wherein the distortion correction circuit unit A second capacitor connected in parallel to the first inductor to change trap selectivity of the first inductor and the first capacitor TV receiver having a video signal distortion correction function further comprising. The method of claim 5, wherein the distortion correction circuit unit And a first resistor connected between the output line of the IF circuit unit and the first inductor to improve insertion loss. The method of claim 6, wherein the distortion correction circuit unit At least one of the first inductor, the first capacitor and the second capacitor is implemented as a variable element, the TV receiver having a video signal distortion correction function, characterized in that configured to vary the trap frequency corresponding to the selected TV broadcast. The method of claim 7, wherein the distortion correction circuit unit In front of the LC trap circuit, a second resistor connected between the output terminal of the IF circuit portion and ground for voltage division and between the output terminal of the IF circuit portion and the first resistor for voltage division; And a third resistor coupled to the TV receiver having a video signal distortion correction function. The method of claim 8, wherein the IF circuit, the distortion correction circuit and the video buffer A TV receiver having a video signal distortion correction function formed in one demodulation IC.

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