SU605342A1 - Device for shaping colour synchronization in "secam" system decoder - Google Patents

Description

one

The invention relates to television and can be used in various television signal transmission systems.

There is a known method of transmitting two black-and-white television programs over a standard television channel, consisting in frequency multiplexing the signals of the first program with frequency-limited signals and of the second program located on the subcarrier frequency in the first field of a television frame, for example, odd, and in the second field of a television frame, for example The signal of the first program is limited in frequency and the signal of the second program transmitted to them in the full frequency band 1.

However, in the known method I1 there is a large crosstalk.

The purpose of the invention is to reduce neipeKpecty1X interference by eliminating the overlap of the signal spectra of transmitted programs.

In this way, in the transmission method of two black-and-white television programs on a standard television channel, which consists in frequency multiplexing of the signals of the first program with frequency-limited signals and of the second program in the first field of a television frame located on the subcarrier frequency frame, for example, even, the signal of the first program is limited in frequency

2

and compacting the second program signal transmitted in the full frequency band in the first field of a TV frame, for example, odd, for one line, transmit the signal of the first program in the full frequency band, during the subsequent line during the joint transmission of frequency-compressed signals of the first program and frequency-limited and located on the subcarrier frequency of the signals of the second program, the spectrum of the signal of the first program is limited to the lower limit of the spectrum of the signal of the second program, and in the second field of the television for example.

Even in the course of a single line, the signals of the second program are transmitted in the full frequency band; during the subsequent line, when the frequency-compressed signals of the second program are combined and the frequency-limited signals of the first program are located on the subcarrier frequency, the spectrum of the second program is limited to the lower limit. signal spectrum of the first program.

FIG. 1 shows a coding scheme; in fig. 2 is a schematic of a decoding device.

The encoder contains two sources 1 and 2 programs connected to

two inputs of electronic switch 3, two

the outputs of which are respectively connected to the inputs of the delay line 4 and the bis filter by one of the inputs of the switch 6. The outputs of the line 4 and of the filter 5 are connected to two other inputs of the switch 6, one output of which is connected via a low-frequency filter 7 to the input of the modulator 8, to the other the input of the latter is energized by the subcarrier frequency. The output of the modulator 8 and the other output of the switch 6 is connected to the inputs of the mixer 9.

The encoder operates as follows.

The output signals f / i and f / a from two sources 1 and 2 of the program are fed to the electronic switch 3, which alternately connects television programs to two different outputs of switch 3 with a frequency of zeros (50 Hz). From one of the outputs of the electronic switch 3, the signals t / i and C / 2 of the first and second programs are fed to the inputs of the delay line 4 and filter 5 and further to the corresponding inputs of the switch 6.

At the outputs of the 4 delay line and the filter 5, two voltages Ui and IJz occur, M series one voltage Ui (Uz} is transmitted in the full frequency band, and voltage U (Uz) in the reduced frequency band. Switch 6 in odd fields There is an alternate connection of signals С // and Ui (and in even fields x-Hi and Uz) with the frequency of lines to the mixer 9. At this time, the signal of another program (in odd fields x - Uz) with a pass through the line enters the input filter a 7 of low frequency and further on to modulator 8, in which the spectrum of the signal of the frequency-limited pro-mm is transferred to higher frequencies. In mixer 9 the signals occurs addition.

The decoding device contains a band-pass filter 10, a line-delay line 11, an electronic switch 12, a low-frequency filter 13, a mixer 14, a demodulator 15, and a switch 16.

The decoding device works as follows.

The common signal f / common receiver arrives at the de-channel. From the output of the band-pass filter 10, a voltage is extracted that carries information about the high-frequency part of the spectrum of transmitted signals.

If the electronic commutator 12 is in a position corresponding to the allocation of an even row of an odd field, then the output of the bandpass filter 10 is the amplitude modulated voltage of the frequency-limited signal of the second program that goes to the demodulator 15 and converts it to a video signal. In this case, the low-frequency part of the spectrum of the transmitted signal, which currently carries information about the first program, is selected by the low-frequency filter 13 and enters the mixer 14, to another input of which, at the same time, the high-frequency part of the previous odd video signal’s spectrum passes through the delay line II strings transmitted in full frequency band.

If the electronic switch 12 is in the position corresponding to the allocation of an odd row of an odd field, then a voltage appears at the output of the band-pass filter 10 carrying information about the high-frequency part of the spectrum of the first program signal. it

voltage is not transmitted anywhere. But at the output of the line 11 delay per line at this time an amplitude-modulated voltage of the frequency-limited signal of the second program, transmitted during the second even line, appears. This voltage arrives at the input of the demodulator 15 and is converted into a video signal of the second program. At the same time, the signal of the first program transmitted in the full frequency band is received

via an electronic switch 12 directly to the input of the mixer 14, to which another input no signal is applied. Therefore, at the output of the mixer 14, the first program's Wits signal is in the full band, which

comes through the switch 16, switched with the frequency of the fields (50 Hz) to the corresponding consumer of information.

Thus, during an odd field, the output of the demodulator 15 on each line is the video signal of the second program in the reduced frequency band, and the output of the mixer 14 on each line is the video signal of the first program in the full frequency band.

The proposed device, in comparison with the known, allows reducing crosstalk.

Claims (1)

1. USSR author's certificate N ° 301875, “l. H 04N 7/08, 1969. CwMfl. cmpoff goig.g.