KR950016223A - NTSC Digital Color Demodulation Apparatus and Method - Google Patents

Abstract

The present invention relates to a digital color demodulation device and method for an ID television receiver.

When demodulating a color image (I) signal that has been modulated and transmitted in a VSB-amplitude modulation scheme, the VSB-amplitude demodulator cannot be used because it is expensive. . Therefore, there is a problem that the resolution of the color image (I) signal is lowered and the image quality is lowered.

The NTSC digital color demodulation device according to the present invention comprises a delay matching unit, a subtractor, an amplifier, and an adder in a conventional color demodulation device, and converts a color image (I) signal modulated by a VSB-amplitude modulation method into an expensive VSB. Demodulate to secure the 1.5 MHz bandwidth of the modulated color image signal without using an amplitude modulator demodulator, and make the amplitude of the high frequency portion of the color image signal (I) equal to the amplitude of the low frequency portion. It improves the resolution of in-phase (I) signal and has the effect of outputting clearer colors.

Description

NTSC Digital Color Demodulation Apparatus and Method

Since this is an open matter, no full text was included.

1 is a characteristic diagram of the frequency spectrum of an NTSC color television signal;

2 is a two-dimensional array diagram when a quadrature modulated color signal of NTSC color television signal is sampled at 4f _sc ,

4 (a) is a block diagram of an NTSC digital color demodulation device according to the present invention, (b) is a characteristic diagram of a frequency spectrum outputted from the NTSC digital color demodulation device according to the present invention,

FIG. 5A is a clock diagram for use in another embodiment of the NTSC digital color demodulation device according to the present invention, and FIG. 5B is a block diagram of another embodiment of the NTSC digital color demodulation device according to the present invention.

Claims (11)

A first latch unit for receiving a demodulated color signal and latching a demodulated color orthogonal signal according to a first clock, a second latch unit for receiving a demodulated color signal and latching a demodulated color image signal according to a second clock; A first low pass filter which receives the signals of the first latch unit and outputs a color orthogonal (Q) signal, and a low pass filter unit which receives the signals of the second latch unit and outputs a color image (I) signal, The low pass filter unit is configured to mutually match an output signal of the second latch unit and an output signal of the second latch unit using the second low pass filter that receives the signal of the second latch unit and the second clock as a synchronization signal. A subtractor that receives a first delay matching unit, an output signal of the second low pass filter, and an output signal of the first delay matching unit, and subtracts an output signal of the second low pass filter from an output signal of the first delay matching unit; Wow, the subtractor An amplifier for amplifying a signal, and an adder for adding the amplified signal and the output signal of the second low pass filter, wherein the amplitude of the high frequency portion of the color image signal (I) output from the low pass filter portion is low. NTSC digital color demodulation device, characterized in that to output a more vivid color by being equal to the amplitude of. The method of claim 1, wherein the first clock is generated for the color orthogonal (Q) signal when the color signal in which the color orthogonal (Q) signal and the color image (I) signal is orthogonally modulated is sampled at four times the frequency of the color carrier. The second clock is generated when the color signal obtained by quadrature modulation of the color orthogonal (Q) signal and the color image (I) signal at a frequency four times that of the color broadcasting broadcast wave. NTSC digital color demodulation device, characterized in that the clock. The NTSC digital color demodulation device according to claim 1, wherein a third low pass filter is formed between the second latch part and the low pass filter part. The cutoff frequency of the first low pass filter is 0.5 MHz, the cutoff frequency of the second low pass filter is 0.5 MHz, and the cutoff frequency of the third low pass filter is 1.5 MHz. NTSC digital color demodulation device. 2. The first absolute value of claim 1, further comprising: a first absolute value connected to the first latch part and the first latch part and the first low pass filter to operate according to a third clock having a frequency twice the first clock frequency. Matching the generator and the first D-flip flip which is operated by the first clock and receives the sign bits among the output signals of the first latch unit, and the output signal of the first D flip-flop is a third click as a synchronization signal. A second delay matching unit, a first inverter for inverting an output signal of the first low pass filter, an output signal of the first low pass filter and an output signal of the first inverter according to an output signal of the second delay matching unit An NTSC digital color demodulation device comprising a first multiplexer for outputting one of the output signals. 6. The NTSC digital color demodulation device according to claim 1 or 5, wherein a cutoff frequency of the first low pass filter is 0.5 MHz, and a cutoff frequency of the second low pass filter is 0.5 MHz. 6. The apparatus of claim 1 or 5, further comprising: a second latch portion operating according to a fourth clock having frequencies twice the second clock frequency, and connected between the second latch portion and the low pass filter portion. 2 Absolute value generator A second D flip-flop that is operated by the second clock and receives a sign bit among the output signals of the first latch unit, and an output signal of the second D flip-flop is used as a synchronous signal. A third delay matching unit, a second inverter for inverting an output signal of the low pass filter unit, an output signal of the low pass filter unit and an output signal of the second inverter according to the output signal of the third delay matching unit; An NTSC digital color demodulation device comprising a second multiplexer for outputting a signal. 8. The NTSC digital color demodulation device of claim 7, wherein a cutoff frequency of the first low pass filter is 0.5 MHz, and a cutoff frequency of the second low pass filter is 0.5 MHz. 8. The NTSC digital color demodulation device according to claim 7, wherein a third low pass filter is provided between the second absolute value generator and the low pass filter. 10. The method of claim 9, wherein the cutoff frequency of the first low pass filter is 0.5 MHz, the cutoff frequency of the second low pass filter is 0.5 MHz, and the cutoff frequency of the third low pass filter is 1.5 MHz. NTSC digital color demodulation device. Separating an input color signal into a demodulated color orthogonal signal and a demodulated color image signal, filtering the corridor color orthogonal signal to output a color orthogonal signal, and filtering a low frequency signal of the demodulated color orthogonal signal Matching the demodulated color image signal and subtracting the low frequency signal from the demodulated color image signal to detect only the high frequency signal of the demodulated color image signal; amplifying the high frequency signal and adding the low frequency signal to the color image signal; NTSC digital color demodulation method comprising the step of outputting. ※ Note: The disclosure is based on the initial application.