SU902318A1 - Device for shaping full television signal in television transmitter - Google Patents

Description

The invention relates to a technique of radio transmitting devices and may be used in television transmitters with a joint amplification of image signals and sound. A device for generating a television signal in a television television is known; a transmitter containing a modularly connected modulator, the first input of which is an input of the image signal, and the second input is the input of a modulating signal, a lower sideband suppression filter, an adder and a cross-sectional gain, and the second input of a follower signal. However, in a known device, it is necessary to use an equalizer and a tracking system to eliminate imitomodulation interference, and the interference suppression is incomplete. The purpose of the invention is to increase the degree of suppression of the inthermodulation interference. This objective is achieved by introducing a series-connected amplitude limiter, a low-pass filter of the chroma signal, an amplitude adjuster and a phase adjuster, the output of which is connected to the device for generating the full television signal. the third input of the adder, while the input of the amplitude limiter is connected with. output filter suppression j lower sideband. The drawing shows the stratum of the Turk electric circuit of the proposed ycfroystva. A device for generating a complete television signal in a television transmitter comprises a modulator 1, a filter for suppressing a lower sideband, an adder 3, a co-amplification path 4, an amplitude limiter 5, a filter 6 for the lower side component of a chroma signal, an amplitude regulator 7, a phase regulator 8 .

The device works as follows.

Modulated in amplitude in modulator 1, the radio frequency image signal passing through filter 2 contains only one upper side component of the chromatic signal, since the lower one is suppressed by filter 2. If there is only one lateral component, the carrier frequency of the image (Fr) turns out to be a modulated chromatic signal (SH-i) both in amplitude and phase, the modulated signal is fed to the input of amplitude limiter 5. The latter suppresses amplitude modulation of the signal and converts pseudo-phase modulation into phase modulation. Performan which on its output side reappears lower component chrominance signal, but inverted in phase. It is entered by a 6n filter with the required ampi- tuity and phase, selected by the controllers 7, and is fed to the input of the adder 3. The controllers 7 and 8 are necessary for compensating for the changes possible in the slower path of the transmitter. To the second input of the adder 3, the carrier frequency of the sound signal is supplied ((|) 04-§.2)

The introduced lower side component of the chrominance frequency signal (W - € 1-) together with the main signal passes through the path 4 of the common amplification. The presence of the specified additional lower side component in the complete signal leads to the fact that intermodulation interference in the transmitter path cannot arise in principle independently of the nature and magnitude of the nonlinearity in us.

Since the chroma signal having a frequency of 51-). modulates the carrier frequency in quadrature, the Q.4 frequency is missing from the full signal envelope, and only 2 Q frequency exists. Therefore, the most intense frequency interference .1) an account of the modulation of the audio signal cannot occur here. However, as a result of the cross modulation that arises from the non-linearity, two components of the same disturbance additionally appear here. One of them is formed by the modulus of the luminance signal (SC)) with a difference frequency of 0.. this creates a UE interference, (Q.2-ft)} —the other part is due to the cross-modulation of the lower side chrominance signal.

Ецв (Шо.) Чв тоой fiij, which is contained in the envelope of the full signal, this forms interference C., С (1о) the two components are equal in amplitude, but opposite in phase, as a result of the interference the frequency Ш © -f-Slfli- completely quenches and can not occur, regardless of the non-linearity of the transmitter.

Other execution of the additionally introduced circuit is also possible. In this case, the filter 6 of the lower side component of the chroma sigal will be connected directly to the input of the filter 2 for suppressing the lower sideband. At the same time, the work of the yCD device will not change.

The technical and economic efficiency of using the proposed device for generating a complete television signal in a television transmitter is that it fully suppresses the most intense intermodulation interference and the level of the latter does not depend on the nonlinearity of the common gain path, and the corrector with the tracking system does not are required.

Claims (1)

Formula from the formula A device for generating a complete television signal in a television transmitter, comprising a modulator connected in series, the first input of which is an input of the image signal and the second input of the modulating signal, a filter for suppressing the lower sideband, an adder and a common amplification path is an audio signal input, characterized in that, in series with the degree of suppression of the intermodulation interference, sequentially connected amplitudes are introduced a limiter, a filter for the lower side component of the chroma signal, an amplitude controller, and a phase controller, the output of which is connected to the third input of the adder, directly the input of the amplitude limiter is connected to the output of the suppression filter of the lower sideband. Sources of information taken into account during the examination i.Revue TectinigTjelVjUnson csF Joivt./ 1978, 10, N9 2, p. 343-390 (prototype)