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The interference analysis of the sound in conference TV system, video and restra
From;    Author:Stand originally

System of 1.1 conferences TV is comprised

Conference TV uses the method of a kind of communication that TV technology and equipment are in two ground through transmitting channel or many places have attending a meeting namely, the integrated processing that it realized the multimedia such as data of frequency, video, text, graph article data, move in same information network, all is transmitted solidly temporarily.

If the cable that transmits these signal carries stronger electromagnetism field district, can interference overlay is in on signal. Cable is longer, interference is more apparent.

Sort of 1.2 interference source reachs interference kind

In conference TV system, the thermal noise that the noise interference that affects video and frequency system divides equipment and transmission line itself and overlay are in what its go up is successional " white noise " outside interference, it is two kinds big according to disturbing source sort to basically can be divided, pulse interference and hum are disturbed. Because the coupling of strong electromagnetism field of generation of pulse parts of an apparatus enters channel be caused by,pulse interference is: Sparkplug of engine of motor, car ignites, switch power source all can produce 60Hz - the interference of 2MHz, the harmonic heft of these interference can fall into frequency band of sound, video inside; Noise of lightning, universe still can produce 2KHz - the impulsive noise of 100MHz. Because design of ground wire system is unreasonable,hum interference basically is, different ground connection nods an existence voltage, make ground electric current forms loop place to cause; High-pressured transmission network and railroad of alternating current aerification also can cause hum to disturb, outside if communicate the interference of electric railway generation,dividing 50Hz fundamental frequency, still have (50Hz of × of 2N + 1) strange second harmonic.

Additional, the transmission track that jams source electromagnetism energy according to the outside and the coupling means to equipment of sound, video can be divided into radiation to means is disturbed and conduct means interference again. Conducting means to disturb is course circuit (it is OK to include stray capacitance and mutual inductance to wait with collect total parameter denotive circuit element) pass suffer on influence equipment, if pulse interference, hum is disturbed, basically pass conduct means action at getting faze equipment; Radiation means interference is the action that carries aerial, pass to the equipment that suffers an effect by the space, if string of high-pressured transmit electricity is right,suffer the interference of faze equipment.

The frequency limits of the frequency signal of conference TV system is 300Hz - 3.4KHz, video signal bandwidth is 6MHz. Frequency signal uses balance means to transmit normally, because noise of double on-line induction has mutual and quits effect, interference should be gotten gently much, measure even do not come out. And video signal uses lopsided pattern to transmit normally, interference is about to be gotten badly much. So frequency disturbs analysis and video interference analysis to distinguish somewhat: To video interference, basically set out from interference means undertake discussing; Frequency signal because wavelengh is bigger, the screen effect of communication building is more apparent, photograph comparing, radiation means interference can be ignorred. Disturb mechanism of signal of pair of sound, video through what the rectification parts of an apparatus such as power source arises pulse identical, solve method to also agree, accordingly, frequency disturbs discussion focal point to be put on hum interference.
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