RU2054824C1 - Digital device for separation of brightness and color signals in pal and ntsc decoders - Google Patents

Abstract

FIELD: TV devices. SUBSTANCE: device has analog-to-digital converter 1, two delay units 2 and 6, subtracter 3, upper frequency filter 4, two multipliers 5 and 8, two tracing low-pass filter 7 and 11, differentiating unit 9, two control signal generators 10 and 12, band-pass filter 13, frequency detector 14, frequency-modulated signal source 15. EFFECT: decreased distortions of brightness and color signals. 1 dwg

Description

 The invention relates to television and can be used in monitors of analog-to-digital hardware-studio complexes of television broadcasting and in television broadcast receivers.

 A digital device for separating luminance and color signals in decoders of PAL and NTSC systems is known, which contains an analog-to-digital converter (ADC) in series, the input of which is the input of the full color video signal (PCVS), the first delay unit and subtractor, the output of which is the output of the digital brightness signal, and a high-pass filter (HPF), the input of which is connected to the output of the ADC.

 A disadvantage of the known device is the presence of distortion of the luminance signal resulting from the notch of the spectrum in the area of deviation of the color subcarrier, and distortion of the color signal due to the superposition on the spectrum of the color signal of the spectrum of the luminance signal.

 The aim of the invention is to reduce the distortion of luminance and color signals.

 In FIG. 1 is a structural electrical diagram of a digital device for separating luminance and color signals in decoders of PAL and NTSC systems; figure 2 shows a graph of the function F g (t).

 The device comprises an ADC 1, a first delay unit 2, a subtractor 3, an HPF 4, a first multiplier 5, a second delay unit 6, a first low-pass filter (LPF) 7, a second multiplier 8, a differentiation unit 9, a first control signal driver 10, and a second SPSF 11, functional converter 12, band-pass filter 13, frequency detector 14 and frequency-modulated (FM) signal generator 15.

 The device operates as follows.

выделяется его высокочастотная (ВЧ) часть

состоящая из ВЧ составляющей сигнала яркости и сигнала цветности. Из спектра сигнала

с помощью фильтра 13 выделяется достаточно узкополосный участок спектра
f_c-

f_s+

где f_s частота цветовой поднесущей;
Δf_пф ширина полосы пропускания фильтра 13, равная, например, 0,5 МГц.PCVS using ADC 1 is converted to digital form, in which all subsequent processing is carried out. Using the low-pass filter 4 from a digital PCVS

its high-frequency (HF) part is highlighted

consisting of the RF component of the luminance signal and the color signal. From signal spectrum

with the help of filter 13, a rather narrow-band portion of the spectrum
f _c -

f _s +

where f _{s the} color subcarrier frequency;
Δf _pf the bandwidth of the filter 13, equal to, for example, 0.5 MHz.

. Сигнал с₁f(t) управляет работой генератора 15 ЧМ-сигнала, который генерирует сигналы W(t) и W*(t) частоты f(t). Сигнал

в первом перемножителе 5 умножается на сигнал W(t), в результате чего его спектр переносится по частоте таким образом, что частота f_s цветовой поднесущей в нем совмещается с нулевой частотой. Этот сигнал задерживается во втором блоке 6 задержки и ограничивается по полосе в первом СФНЧ 7, после чего во втором перемножителе 8 он умножается на сигнал W*(t), в результате чего осуществляется перенос его спектра, обратный по отношению к переносу, осуществляемому в результате умножения сигнала S_вч на сигнал W(t) в первом перемножителе 5.The frequency detector 14, as a result of detecting the signal at the output of the filter 13, produces a signal with ₁ f (y) proportional to the instantaneous frequency f (t) of the color signal, which changes when color transitions occur as a result of a change in the instantaneous phase Φ (t) of the color signal associated with instantaneous frequency ratio f (t)

. The signal from ₁ f (t) controls the operation of the FM signal generator 15, which generates signals W (t) and W * (t) of frequency f (t). Signal

in the first multiplier 5 is multiplied by the signal W (t), as a result of which its spectrum is transferred in frequency so that the frequency f _{s of the} color subcarrier in it is combined with the zero frequency. This signal is delayed in the second delay block 6 and limited by the band in the first LPF 7, after which it is multiplied by the signal W * (t) in the second multiplier 8, as a result of which its spectrum is transferred inverse to the transfer carried out as a result multiplying the signal S _RF by the signal W (t) in the first multiplier 5.

The signal from the output of the second delay unit 6 is also subjected to filtering in the second LPF 11, as a result of which a digital color signal is generated, the spectrum of which is transferred to the zero frequency. The spectrum transfer and processing in the first and second LPFs 7 and 11 are equivalent to bandpass filtering with a change in the center frequency of filter 13 according to the law corresponding to a change in the instantaneous frequency of the S _RF signal, which allows matching the filtering characteristic with the current color signal frequency.

Под действием сигнала g(t) происходит изменение полосы пропускания первого СФНЧ 7, например, по закону
Δf cg(t)|
Таким образом, чем больше производная составляющая u(t) и v(t) цветовой поднесущей, тем шире полоса пропускания первого СФНЧ 7.The first LPF 7 is constructed in such a way that it is a narrow-band filter in the areas of a slow change in the amplitudes of the quadrature components u (t) and v (t) of the color signal, and its bandwidth expands when sharp jumps u (t) and v (t) are transmitted. To do this, using the differentiation unit 9, a complex signal u '(t) + iv' (t) is formed, the components of which take maximum values when transmitting contrasting color transitions with a change in saturation or color tone. The first driver 10 of the control signal is used to generate a signal that characterizes simultaneously the manifestation of a rapid change of signals u (t) and v (t), and may have a conversion characteristic, for example, determined by law
g (t)

Under the action of the signal g (t), the passband of the first LPF 7 changes, for example, according to the law
Δf cg (t) |
Thus, the larger the derivative component u (t) and v (t) of the color subcarrier, the wider the bandwidth of the first LPF 7.

 The law of changing the passband of the second UHF 11 may differ from the law of changing the bandwidth of the first UHF 7, since the purpose of the signal conversion in the first UHF 7 is to effectively suppress the luminance interference from the color signal, and the purpose of the signal conversion in the second UHF 7 is to provide effective noise suppression in the channel color from luminance signal. Possible laws of the dependence of the passbands of the first and second LPFs 7 and 11 on the signal g (t) | are shown in figure 2 (curves 1 and 2).

 Blocks 5, 6, 7, 8, 9, are made in the form of complex signal processing devices.

The signals at the output of the FM generator 15 are determined by the formulas
W (t) e ^{i 2 π f} s ^t ;
W * (t) e ^{- i 2 π f} s ^t .

 The first multiplier 5 is a multiplier of the material and complex signals with the output of the complex signal, the second multiplier 8 is the multiplier of the second complex signals with the output of the material signal.

Signal HF component PTSVS after processing at blocks 5, 6, 7 is a signal S _HF, wherein the maximum interference is suppressed by the HF-component of the luminance signal. After the reverse frequency transfer in the second multiplier 8, this signal is subtracted from the PCVS, as a result of which a luminance signal is generated in which the interference from the color signal is suppressed to the maximum extent.

 The color signal C is a complex signal, the real and imaginary parts of which are digital signals of the quadrature components u (t) and v (t) of the complex envelope of the color signal.

Claims (1)

 DIGITAL BRIGHTNESS AND COLOR SIGNALING DIGITAL DEVICE IN PAL AND NTSC SYSTEM DECODERS, containing an analog-to-digital converter (ADC) in series, the input of which is the input of the full color video signal, the first delay unit and the subtractor, the output of which is the output of the brightness signal, the high-pass filter is connected in series frequency (HPF), the input of which is connected to the ADC output, and the first multiplier, a bandpass filter, a detector and a second multiplier, the output of which is connected to the second input of the subtractor, I distinguish the fact that the detector is frequency-controlled and a second delay block is connected in series, the input of which is connected to the output of the first multiplier, and a first low-pass filter (LPF), the output of which is connected to the first input of the second multiplier, the differentiation unit is connected in series, the input of which is connected with the output of the first multiplier, and the first driver of the control signal, the output of which is connected to the control input of the first servo low-pass filter, the second servo low-pass filter, the input of which is connected to the input m of the first tracking LPF, and the output is the output of the chrominance signal, the second driver of the control signal, the input of which is connected to the output of the differentiation unit, and the output is the control input of the second tracking LPF, the generator of the frequency-modulated signal, the input of which is connected to the output of the frequency detector, the first the output is with the second input of the first multiplier, and the second output is with the second input of the second multiplier, a band-pass filter is connected between the output of the HPF and the input of the frequency detector.

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