SU985971A1 - Method of shaping high-frequency television signal - Google Patents

Description

(54) METHOD OF FORMING A HIGH-FREQUENCY TV SIGNAL

one

The invention relates to a television technique and can be used to transmit and retransmit television signals.

There is a known method of generating a high frequency signal, comprising E generating a high frequency carrier signal and then modulating it with a full television signal 11.

However, the known method imposes very strict requirements on the frequency stability (not worse, i 1 Hz) of the carrier frequencies of all television transmitters operating in this frequency channel. The presence of transponders with an unstable carrier frequency, operating in the same frequency channel, leads to the appearance of an interfering pattern on E1fan, caused by beats, of a received high-frequency signal with the high-frequency signal of another television repeater, operating in the same frequency channel.

The purpose of the invention is to reduce the requirements for stability of the carrier frequency generator and increase the noise immunity of the traced television signal.

To this end, in the method of formation. a high-frequency TV signal, and & kpyuchak. in the formation of a carrier signal with subsequent modulation of its full television signal, before modulating the carrier frequency signal from the full TV signal, separate the signals, lines and fields, form a switching signal whose frequency ra: on

- F

 at J1 - g

ke with c ht

where hi t € I and K are mutually forgiven among 20 la, with KP-ef, and

Claims (1)

fc is the line frequency; .f - field frequency. and switching the phase of the signal of the frequency carrier in accordance with the switching signal during the reverse stroke of the sweeps. The drawing shows a structural electrical circuit of a device that implements a method for generating a high-frequency TV signal. The device contains a sync selector 1, a driver 2, a phase manipulator 3, an exciter 4, an amplitude modulator 5. A method of forming a high-frequency TV signal with two translators operating in the same frequency channel can be performed as follows. The exciter 4 generates a carrier signal, while simultaneously with the synchro selector 1 ramming, signals with a frequency of lines and fields are made from the full television signal, and a pulse switching signal is generated from these signals by the shaper 2 with e, e J K where at, K1 1; the phase manipulator switches the carrier frequency signal to 180 with the frequency f during the time corresponding to the sync impulses of the rows and fields of the full television signal, and then the carrier frequency signal is modulated according to the amplitude of the full television channel in the amplitude modulator 5. The phase switching law is set by the choice of the duration and frequency of the pulse switching of the driver, (the choice of AND, VH, K and P) The phase switching law itself is selected according to frequency planning requirements. Considering that the signal emitted by a TV / radio transmitter contains an FM sound signal and that editing the phase carrying the image could cause cross-section distortion in the sound channel of the & levizionnogo receiver, the image carrying phase in the transmission of damping pulses of a TV signal. On repeaters with transfer of the TV signal spectrum, the proposed method is implemented in a similar way by switching the phase not of the received carrier itself, but of the HF oscillations of the transponder heterodyne. The positive effect of the implementation of the invention lies in the transition of the entire network, including low-power radio transmitters and repeaters, 6 mode of operation, using frequency channels more economically than the simple VLF mode. The economic effect is determined by the lower cost of the device that implements the method, in addition, the invention allows to increase the noise immunity of the broadcast television signals, which distinguishes it from the prototype. Claim method A method of generating a high frequency TV signal, comprising generating a signal of a frequency subsystem followed by modulating it with a full television signal, characterized in that, in order to increase the noise immunity, before modulating the carrier signal from the full TV signal, the signals of fields that form a switching signal from them, whose frequency is equal to r JTLr. and р С Е ic К п where W, е, and and k are mutually simple numbers, and ki С, а and К; 1s - the frequency of the lines; f p is the frequency of the drink and the phase of the signal of the carrier frequency is switched in accordance with the switching signal during the reverse run of the sweeps. Sources of information taken into account in the examination 1. Electrosv s, 1976, № 3, p.40.