KR0141679B1 - High pass compensation circuit of digital com filter - Google Patents

Abstract

In the characteristic improvement circuit of the image processing apparatus, the signal input to the composite video input terminal (CVC) is filtered at 7MHZ low pass, and the signal is filtered at 7MHZ high pass to the composite video input end (CVC).

The low pass filtering 7MHZ video signal is converted into digital data by the 4fsc signal, and then processed by the 4fsc signal and separated by luminance (Y) and color (C).

Time according to the propagation delay after converting the analog (C) and analog (C) signals of the luminance (Y) and the color (C) by the color (C) and luminance (Y) signals separated by the digital processing and the Y / C separation unit. To compensate for this, and adds the luminance signal and the output luminance signal to output a high resolution video signal.

Description

High Compensation Circuit of Digital Comb Filter

1 is a circuit diagram according to the present invention

2 is an operational waveform diagram of FIG.

The present invention relates to a high frequency compensation circuit in high resolution color monitors and television receivers, and more particularly, to a high frequency compensation circuit for improving frequency characteristics in a digital comb filter.

In general, the digital comb filter used for Y / C separation of a high resolution color monitor and a television receiver uses a 7MHZ low pass filter (LPF) to eliminate aliasing. The low pass filter LPF is naturally unable to reproduce a video signal of a high frequency portion of 7 MHZ or more in accordance with signal processing. In addition, the sampling frequency used in the digital comb filter is 4 quadrature of 3.58MHZ, that is, 4fsc frequency, and the frequency (video signal) component corresponding to 1/2 of the sampling frequency, that is, the frequency component of 7MHZ or more is as described above. Eliminated due to aliasing that occurs during sampling. Therefore, the signal of 7MHZ or more, which has passed through the low pass filter 101, is also input to the digital comb filter unit 100 and processed. Therefore, the frequency characteristic is deteriorated automatically due to the above reason. As such, if the frequency characteristic of 7MHZ or more is bad, when the high resolution of 800 or more is required, such as a master monitor, the digital comb filter unit 100 is designed to compensate for this and input the signal to it. .

Accordingly, an object of the present invention is to provide a circuit for boosting a high frequency to improve frequency characteristics.

Another object of the present invention is to provide a circuit capable of compensating for a high frequency frequency by combining an output luminance signal Y of a digital comb filter with a video signal input as an existing original signal.

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

1 is a circuit diagram according to the present invention,

A low pass filter 101 for filtering a signal input to the composite video input terminal (CVC) at a low frequency of 7 MHz;

A high pass filter 107 for passing a signal input to the composite video input terminal (CVC) through a high frequency band of 7 MHz;

An A / D converter 102 for converting the video signal of the pass band 7MHZ of the low pass filter 101 into digital data by an input signal of 4fsc stage;

A digital processing and Y / C separation unit 103 for processing the output digital data of the A / D conversion unit 102 by a signal of 4 fsc stages and separating them by luminance (Y) and color (C);

The digital luminance (Y) and color (C) data are converted into analog signals by the signals of the 4fsc stage for each of the color (C) and luminance (Y) signals separated by the digital processing and the Y / C separation unit 103. A D / A conversion unit 104,

A delay circuit 108 for delaying the output of the high-frequency 7MHZ passing through the high pass filter 107 to be compensated by the time due to propagation delay in the comb filter unit 100;

The luminance signal Y'd (tn) converted into analog by the D / A converter 104 and the luminance signal Y'd (tn) output from the delay circuit 108 are added to the original. An adder 105 for compensating for the high range of luminance in the 7 MHz band,

Y and C processing units 106 for receiving and processing the output of the adder 105 and the output of the D / A converter 104 to output a video signal compensated for the high-frequency luminance characteristics.

2 is a waveform diagram according to the present invention, i.e., (2a)-(2e) is an example showing the output state of each output terminal (A)-(D) in FIG.

Therefore, a specific example of the present invention will be described in detail with reference to FIGS. 1 to 2.

According to the present invention, when a high resolution of 800 or more is required like a master monitor, more than 560 or more can be theoretically inputted through the digital comb filter unit 100. Therefore, when a high resolution is required, as shown in FIG. 1, a 7MHZ band is passed through the high pass filter 107 of the input composite video signal (CVC) as shown in FIG. On the other hand, when the low-pass filter 101 passes the signal of 7MHZ band is as shown in (2b). The A / D converter 102 converts the digital data into digital data according to the 4fsc signal. The signal converted into the output digital data of the A / D converter 102 is separated into luminance (Y) and color (C) by the digital processing and the Y / C separator (103), and is converted by the D / A converter (104). Each converts to an analog signal. The digital processing and the Y / C separator 103 output an analog luminance signal Y'd (t-n) as shown in (2c). The signal of the composite video signal stage (CVC) is delayed in the delay circuit 108 by filtering the high frequency of 7MHZ or more in the high pass filter 107, but the radio wave generated by the digital comb filtering of the digital comb filter unit 100. In order to compensate for the delay, the output of the D / A converter 104 is added to the output of the D / A converter 104 and delayed as shown in FIG. The adder 105 delays and adds the original 7MHZ signal of (2b) passed by the high pass filter 107 in the delay circuit 108 as it is and is generated as (2d) so that it is originally generated in the region of 7MHZ or more. Compensated by the frequency characteristic of Therefore, when the output [Y '(tn)] of the adder 105 and the output of the D / A converter 104 are processed by the Y and C processing units 106, the output of the adder 105 is also compensated for. A good video signal can be obtained without loss of frequency characteristics. In other words, the time t used herein passes the video signal CVC through the high pass filter 107 in order to solve the conventional problem in the high range, so that the digital comb filter unit 100 in the delay circuit 108 The propagation time is added as much as the propagation delay time generated in the signal processing to compensate for the high frequency. An additional delay time is added for temporal matching of Y'd (t-n) (2c) and Y '(t-n) (2c) in FIG. In conclusion, the original 7MHZ is moved to the high frequency as it is, and the high frequency characteristic of 7MHZ or more is compensated. Therefore, a high resolution image can be obtained.

As described above, the 7MHZ of the luminance Y signal and the existing input video signal of the digital comb filter are shifted to a high frequency to compensate for 7MHZ or more. Therefore, the high-frequency image is improved by improving the high frequency characteristics.

Claims (1)

In the high frequency characteristic improvement circuit of an image processing apparatus, A low pass filter 101 for filtering a signal input to the composite video input terminal (CVC) of the image processing device at a low frequency of 7 MHz; A high pass filter 107 for passing a signal input to the composite video input terminal (CVC) through a high frequency band of 7 MHz; An A / D converter 102 for converting the video signal of the pass band 7MHZ of the low pass filter 101 into digital data by an input signal of 4 times (4fsc) of the sampling frequency fsc of the video signal; , A digital processing and Y / C separation unit 103 for processing the output digital data of the A / D conversion unit 102 by the signal of the 4fsc stage and separating the luminance data by the luminance (Y) and the color (C); Digital luminance (Y) and color (C) data are converted into analog signals by the signals of the 4fsc stage for each of the color C and luminance Y signals separated by the digital processing and the Y / C separation unit 103. D / A conversion unit 104 to be. Delay circuit 108 for delaying the output of the high-frequency 7MHZ passing through the high pass filter 107 by the time due to the propagation delay in the comb filter unit 100, The luminance signal Y'd (tn) converted to analog by the D / A converter 104 and the luminance signal Y'd (tn) output of the delay circuit 108 are added to the original signal. An adder 105 for compensating for the 7MHZ band at a high frequency of 7MHZ or more, Digital comb, characterized in that composed of the Y and C processing unit 106 for receiving the output of the adder 105 and the output of the D / A converter 104 to output a video signal compensated for the high frequency characteristics High-pass compensation circuit of the filter.