KR20000043172A - Single secam color signal demodulator using two reference frequencies - Google Patents

Abstract

PURPOSE: A single SECAM color signal demodulator is provided to reduce the manufacture cost while preventing the deterioration of the demodulating capability by employing a common demodulator using two carrier signals. CONSTITUTION: A quadrature type demodulator(100) inputs a composite color signal of the SECOM type to provide a demodulated color difference signal with the elimination of noise. A frequency generator(200) inputs a demodulation reference frequency and provides a first reference frequency and a second reference frequency. A filter tuner(300) inputs the first reference frequency, the second reference frequency, and the demodulated color signal to provide a filter tuning signal. A permutator(400) outputs a demodulated color difference signal(B-Y) of blue color series.

Description

Single SEAM Color Signal Demodulator Using Two Reference Frequencies

The present invention relates to a single SECAM color signal demodulator using two reference frequencies of a television, and in particular, a separate SECAM using a red and blue FM carrier frequency of 4.406 MHz / 4.25 MHz. The present invention relates to a single SECAM color signal demodulator using two reference frequencies in which an area of an integrated circuit (IC) chip is reduced by implementing a color signal demodulator using one single demodulator.

SECAM method is a TV signal system used in France, Russia, Iraq, etc. NTSC and PAL system is the amplitude modulation (AM) of the video signal to transmit.

Since NTSC and PAL are amplitude modulation (AM) methods, two signals, a red color difference signal RY and a blue color difference signal BY, as shown in FIG. 1A using a quadrature method. Can be mixed and transmitted in one carrier signal.

Since the frequency modulation (FM) method is not possible, the two color difference signals R-Y and B-Y are sequentially transmitted. Referring to FIG. 1B, the frequency of a carrier signal used for modulation of each color difference signal is 4.406 MHz in the red color difference signal RY, and 4.25 MHz in the blue color difference signal BY. use. Advantageously, in NTSC and PAL, the phase difference, which is the angle between two chrominance signals, can be deformed during the transmission process, making it difficult to reproduce the original color when the actual TV signal is received. Because of the (FM) signal, the signal-to-noise (S / N) ratio is excellent, making the original color reproduction much easier when receiving television.

2 is a conventional separate SECAM color signal demodulator. Referring to FIG. 2, the separate SECAM color signal demodulator includes a permutator (1), a first phase shifter (2), a first biquad filter (3), and a first phase detector (Phase). Detector: 4), first filter tuner (5), first de-emphasis (6), second phase shifter (7), second biquad filter (8), second It consists of a phase detector 9, a second filter tuner 10 and a second de-emphasis 11.

The permutator 1 receives a composite color signal of the SECAM method and separates the sequential red (D'R) and blue (D'B) color signals to separate the red-based color signal (D'R). Is provided to the first phase shifter 2 and the blue color signal D'B is provided to the second phase shifter 7.

The first phase shifter 2 receives the reference frequency of 4.43 MHz and the red-based color signal D'R to shift the phase to shift the phase-shifted red-based color signal to the first biquad filter 3 and To the first phase detector 4.

The first biquad filter 3 receives the phase shifted red-based color signal and filter correction control current and delays the signal to provide the red-based color signal with the delayed signal to the first phase detector 4.

The first phase detector 4 receives a red-based color signal of which the signal is delayed and a red-based color signal of which phase is shifted, detects a phase, and demodulates the demodulated color signal to the first filter tuner 5 and the first de-emphasis. 6) to provide.

The first filter tuner 5 receives the demodulated color signal and provides a control current for filter correction.

The first de-emphasis 6 receives the demodulated color signal and restores the pre-emphasized signal to a frequency modulated (FM) signal to remove noise to remove the demodulated color difference signal RY. Output

The second phase shifter 7 receives a reference frequency of 4.43 MHz and the blue-based color signal D'B to shift the phase to shift the phase-shifted blue-based color signal to the second biquad filter 8 and A second phase detector 9 is provided.

The second biquad filter 8 receives the phase shifted blue-based color signal and filter correction control current and delays the signal to provide the second-phase detector 9 with a blue-based color signal with a delayed signal.

The second phase detector 9 detects a phase by receiving a blue-based color signal with a delayed signal and a blue-based color signal with a phase shift, and detects a demodulated color signal from the second filter tuner 10 and the first de-emphasis. 11) to provide.

The second filter tuner 10 receives the demodulated color signal and provides the filter correction control current.

The second de-emphasis 11 receives the demodulated color signal and restores a pre-emphasized signal to a frequency modulated (FM) signal to remove noise to output a demodulated blue color difference signal BY. do.

The operation principle of the quadrature demodulator 100 is described below with reference to FIG. 5.

Since the general input frequency modulation (FM) signal f _FM (t) can be seen in Equation (1), it can be seen that demodulation of the FM signal is achieved by frequency modulation.

v (t) = k = k = kf (t)

The SECAM chroma signal is a frequency modulated (FM) signal with a fundamental frequency of 4.406 MHz for the red series and 4.25 MHz for the blue series. Due to the difference in the previous carrier frequency, the demodulation is separated into a red series (D'R) and a blue series (D'B) before the demodulation step. In addition, since it is a frequency-modulated (FM) signal, it is very sensitive to phase distortion, so the biquad filter used inside the demodulator tunes every horizontal period using the reference frequency of 4.43 MHz. .

However, in the prior art, the total area is increased by demodulating according to the red and blue signals, and the red and blue color difference signals RY and blue based color difference signals BY are separately demodulated by using two demodulators. There is a problem that a level difference may occur.

The present invention has been proposed to solve the above problems, and an object of the present invention is to reduce the number of quadrature demodulators used in SECAM type color signal demodulators and reduce the frequency of red and blue FM carrier frequencies ( A single SECAM color signal demodulator using two reference frequencies to reduce the area required on an integrated circuit (IC) using a conventional separate SECAM color signal demodulator as a single demodulator using the carrier frequency 4.406 MHz / 4.25 MHz do.

FIG. 1A is a waveform diagram illustrating two color difference signals RY and BY mixed in an orthogonal manner and transmitted to a carrier signal in the SECAM method, and FIG. 1B shows two color difference signals RY and BY Is a waveform diagram showing that is sequentially transmitted;

2 is a conventional discrete SECAM color signal demodulator;

3 is a single SECAM color signal demodulator using two reference frequencies according to an embodiment of the present invention;

4 is a color signal input to a SECAM demodulator; And

5 is a block diagram illustrating an operation principle of a general quadrature demodulator.

<Description of the code | symbol about the principal part of drawing>

100: Quadrature demodulator

110: phase shifter 120: biquad filter

130: phase detector 140: de-emphasis

200: frequency generator

300: Filter Tuning 400: Permutator

In order to achieve the above object, the present invention provides a television using a SECAM method, orthogonal demodulation unit for providing a demodulated color difference signal by removing the noise received from the mixed color signal of the SECAM method; A frequency generator for receiving a demodulation reference frequency and providing a first reference frequency and a second reference frequency; A filter tuner for receiving a first reference frequency, a second reference frequency, and a demodulated color signal to provide a filter tuning signal; And receiving the demodulated color difference signal by removing the noise, and separating the sequentially input red (D'R), blue (D'B), red (D'R), and blue (D'B) color signals. A single SECAM color signal using two reference frequencies, characterized in that it consists of a permutator for outputting the demodulated red-based color difference signal (RY) with noise removed and the demodulated blue-based color difference signal (BY). Provide a demodulator.

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

3 is a single SECAM color signal demodulator using two reference frequencies according to an embodiment of the present invention. The single SECAM color signal demodulator includes an orthogonal demodulation unit 100, a frequency generator 200, a filter tuner 300, and a permutator 400.

The quadrature demodulator 100 includes a phase shifter 110, a biquad filter 120, a phase detector 130, and a de-emphasis 140.

The orthogonal demodulation unit 100 receives the SECAM mixed color signal 101 and provides the demodulated color difference signal 141 to the permutator 400 by removing noise.

The phase shifter 110 receives the SECAM mixed color signal 101 and shifts a phase to shift the phase shifted mixed color signals 111 and 112 of the biquad filter 120, respectively. And to the phase detector 130.

The biquad filter 120 receives the phase shifted SECAM type mixed color signal 111 and delays the signal to provide the phase-detector 130 with the red signal of the delayed red series.

The phase detector 130 detects a phase by receiving the phase shifted SECAM type mixed color signal 112 and the delayed red color color signal 121 and decodes the demodulated color signals 131 and 132 respectively. 140 and the filter tuner (300).

The de-emphasis 140 receives the demodulated color signal 131 and restores a pre-emphasized signal to a frequency modulated (FM) signal to remove noise to remove the demodulated color difference signal 141 from the permutator. Provided at 400.

The frequency generator 200 receives a 4.43 MHz 109 that is a reference frequency for demodulation and provides a frequency 201 of 4.406 MHz and a frequency 202 of 4.25 MHz.

The filter tuner 300 receives the frequency 201 of 4.406 MHz and the frequency 202 of 4.25 MHz to provide a filter tuning signal 301.

The permutator 400 receives the demodulated color difference signal 141 by removing the noise and sequentially inputs red (D'R), blue (D'B), red (D'R), and blue (D) signals. A color signal of 'B) is separated to remove noise, and a demodulated red color difference signal RY and a noise are removed to output a demodulated blue color difference signal BY.

Referring to FIG. 4, the color signal input to the SECAM demodulator according to the present invention has a horizontal blanking in which a red color signal D'R and a blue color signal D'B are sequentially about 10 μsec. A filter tuning of the biquad filter 120 is performed by the filter tuner 300 with a horizontal blanking section.

The single SECAM color signal demodulator using the two reference frequencies according to the present invention is based on the 4.25 MHz, 4.406 MHz, which is the carrier frequency of each blue and red series in the horizontal blanking section of about 10 μsec. Filter tuning is performed as a signal. In this case, the filter tuning is performed by vertical blanking when 4.43 MHz is used. Therefore, a loop filter having a time constant in msec is required, while a time constant of about 100 μsec is required. Since the loop filter is greatly reduced in size, a more compact demodulator can be implemented.

In addition, the filter tuner 300 uses a frequency of 4.406 MHz for the red color difference signal RY and 4.25 MHz for the blue color difference signal BY to sequentially apply the biquad filter 120. Will be synchronized.

Therefore, the common demodulator using two carrier frequency signals of 4.406 MHz for red color difference signal (RY) and 4.25 MHz for blue color difference signal (BY) can reduce the area of integrated circuit and reduce manufacturing cost. have.

As described above, a single SECAM color signal demodulator using two reference frequencies according to the present invention occupies a large area due to internal capacitors and resistors when a quadrature SECAM signal demodulator is implemented on an integrated circuit (IC). In the case of the common demodulator method using two carrier signals of 4.406 MHz / 4.25 MHz, the area of the integrated circuit of the demodulator can be reduced by half without degrading the demodulation performance. Therefore, the manufacturing cost can be reduced.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art can variously modify and change the present invention without departing from the spirit of the invention described in the claims below. You will understand.

Claims (3)

In televisions using the SECAM method, An orthogonal demodulation unit 100 for receiving a SECAM composite color signal 101 and providing a demodulated color difference signal 141 by removing noise; A frequency generator 200 for receiving a demodulation reference frequency 109 and providing a first reference frequency 201 and a second reference frequency 202; A filter tuner (300) for receiving the first reference frequency (201), the second reference frequency (202), and the demodulated color signal (132) to provide a filter tune signal (301); And The noise is removed and the demodulated color difference signal 141 is input to sequentially receive the red (D'R), blue (D'B), red (D'R), and blue (D'B) color signals. Two reference frequencies, characterized in that consisting of a permutator 400 for outputting a demodulated red-based color difference signal (RY) and a noise-removed demodulated blue-based color difference signal (BY). Single SECAM color signal demodulator using The method of claim 1, wherein the orthogonal demodulation unit 100 A phase shifter 110 for receiving the SECAM type mixed color signal 101 and shifting a phase to provide a phase shifted mixed color signal 111 or 112; A biquad filter (120) for receiving the phase shifted SECAM type mixed color signal (111) and delaying the signal to provide a red signal (121) having a delayed signal; A phase detector (130) for detecting a phase by receiving the phase shifted SECAM type mixed color signal (112) and the delayed red color signal (121) and providing a demodulated color signal (131, 132); And And a de-emphasis 140 configured to receive the demodulated color signal 131 and restore the pre-emphasized signal to an FM signal to provide a demodulated color difference signal 141 by removing noise. Single SECAM color signal demodulator using two reference frequencies. The method of claim 1, wherein the filter tuner (300) The biquad filter 120 is tuned by sequentially using a first reference frequency of 4.406 MHz for the red color difference signal RY and a second reference frequency of 4.25 MHz for the blue color difference signal BY. A single SECAM color signal demodulator using two reference frequencies.