RU1807583C - Method of formation of chrominance signal in secam system and device for its implementation - Google Patents

Abstract

The method for generating a color signal of the SECAM system and a device for its implementation are used in television technology, in particular in telecenter coding devices. The essence of the invention lies in the fact that they carry out low-frequency (LF) predistortion of the color difference signal, generate a frequency-modulated (IM) signal of the color subcarrier, carry out its high-frequency (HF) predistortion and limit the received signal in the frequency band, generate the envelope of the MF signal, multiply it by the signal of the frequency of rest of the color subcarrier, perform the RF predistortion of the signal and limit the frequency band. The device for its implementation contains a block of low-frequency predistortions, analog-digital converter (ADC), envelope generator of the FM signal, 1 high-frequency predistortion block, 1 low-pass filter, 1 multiplier, 1 digital-to-analog converter, frequency signal generator of the rest frequency color subcarrier. 2 s.p. f-ly, 3 ill.

Description

The invention relates to television technology, in particular to telecenter coding devices.

The purpose of the invention is to reduce the distortion of color difference signals,

A method for generating a color signal in the SECAM system consists in performing a low-frequency pre-emphasis of a color-difference signal, generating a frequency-modulated (FM) color subcarrier signal and performing its high-frequency (HF) pre-emphasis and limiting the resulting spectrum over a frequency band, generating a color sub-carrier signal , carried out immediately after the low-frequency predistortions, while generating the complex envelope of the FM signal and multiplying it by the complex

the resting frequency signal is a color subcarrier, and the RF pre-emphasis signal and band limiting are performed over the complex envelope.

The invention is illustrated in FIG. 1, 2 and 3.

A known device (see Fig. 1) for generating a color signal of the SECAM system (prototype), which implements the known method, comprises a low-frequency (LF) predistortion block 1, a limiter 2, a frequency-modulated (FM) generator 3, a high-frequency (HF) predistortion block 4, bandpass filter 5.

The structural electric circuit of the proposed device for generating a color signal of the SECAM system that implements the proposed method contains (see Fig. 2) a low-frequency prediction block00

about

and

00

with

1, analog-to-digital converter 6, complex envelope generator for FM signal 7, high-frequency (HF) predistortion unit in the form of low-frequency equivalent 8, low-pass filter 9, multiply 10, digital-to-analog converter FM signal 11, generator of complex frequency signal color subcarrier 12.

The FM complex envelope generator can be constructed according to the block diagram shown in FIG. 3, on which is indicated: a signal multiplier by a constant coefficient C1, proportional to the frequency deviation of 13, 5 delay elements 14, 15, 16, 17, 18, 4 multipliers by constant coefficients AO, A, A + S 18, 19, 20 , 21, a multi-input adder 22, a storage device (EPROM) 24 with a recorded sine table, a storage device (EPROM) 25 with a recorded table of cosines.

A device for generating a color signal of the SECAM system operates as follows. .

The color difference signal is fed to the input of the low-frequency predistortion unit 1, where the high-frequency components of its spectrum are raised, the output of the low-frequency predistortion block, the signal is fed to the ADC 6, where it is converted to a parallel digital code, which is fed to the generator of the complex envelope of the FM signal 7, where is converted into a digital complex envelope signal, which is fed to the high-frequency pre-emphasis unit 8, whose frequency response corresponds to the LF equivalent.

From the output of the RF predistortion unit 8, the complex envelope signal of the color subcarrier enters the low-pass filter (LPF) 9, where the spectrum of the complex envelope of the FM signal is limited. From the output of the low-pass filter 9, the signal is fed to the multiplier 10, to the second input of which the signal from the generator of the complex signal of the frequency of rest of the color subcarrier 12. In the multiplier 10, the limited spectrum of the complex envelope of the FM signal is transferred to the subcarrier frequency, i.e. the negative consequences of widening the frequency band will be excluded

signal due to increased frequency deviation associated with the exclusion of emission limits at the output of the low-frequency predistortion block 1. From the output of the multiplier 10, the received signal is fed to a digital-to-analog converter (DAC) 11.

Claims (2)

1. A method for generating a color signal of the SECAM system, namely, that a low-frequency low-frequency predistortion of a color difference signal is performed, a frequency-modulated (FM) color subcarrier signal is generated and its high-frequency (high-frequency) predistortion is performed, and the resulting spectrum is limited by the frequency band, characterized in that, in order to reduce distortion of color difference signals, the generation of a color signal. the gross subcarrier is carried out immediately after the LF predistortions, the complex envelope of the FM signal is generated and multiplied by the complex signal of the frequency of the rest of the color subcarrier, and the HF signal predistortion and band limitation, the frequencies are carried out by the complex envelope. 2. A device for generating a color signal in the SECAM system, comprising an LF predistortion block, an FM signal generator, an HF predistortion block, characterized in that an ADC, a DAC, a complex envelope envelope of the FM signal, a complex signal generator of the color rest subcarrier frequency, 1 multiplier and Low-pass filter, and the high-frequency predistortion block is made in the form of the low-frequency equivalent of the high-frequency predistortion block with a complex transmission coefficient corresponding to the SECAM standard, and the low-frequency predistortion block, ADC, the complex envelope generator FM Nala, equivalent LF RF predistortion unit and the LPF are connected in series between the input device and a first multiplication input, to the second input of which the output of the generator of the complex resting frequency signal of the color subcarrier is connected, and the output of the multiplier is connected to the input of the DAC, the output of which is the output of the device.