Video signal interference causes and solutions

Video signal interference generated

1, front-end power interference: elevator frequency conversion motor, the factory of high-power motors, substation, and so on.

2. transmission of electromagnetic interference: mainly radio interference, such as, telecommunications base station, there are cable damage caused by the interference and to potential interference, etc.

3. terminal equipment interference: mainly device power interference and connection caused by interference.

Video signal interference solution

1. to determine the location of interference from front end to check the camera there is no interference, if any, usually the power to go (you can use 12V battery-powered test whether power interference), you can switch the power supply to the camera, you can also install the AC filter to filter, and generally can solve;

2. If, through the transfer process, first check the video cables, shielded network without damage, and in addition you can select a antijamming considered, at present, the market of the basic principles of a antijamming two kinds, one kind is the video baseband signal modulated to 38MHZ or higher, to avoid interference frequency, its effect, but is experiencing interference frequency and 38MHZ close, then there is no way out; another is the use of the video signal on the front-end for amplitude increase zoom options, and then compressed in the Terminal, because the interference signal amplitude is unchanged, the interference signal will be compressed, this is a broad-spectrum anti-jamming, but there are certain residues that EMI effect depends on the magnitude of the video signal amplification and signal interference, the larger the margins, the closer the front end, interference interference effects better.

3. If you used a antijamming effect is not evident, it is possible that the Terminal (room), so you need to check the connections, power, ground and the device itself issues.

Coaxial cable is the most widely used video transmission media, typically used in short-distance transport of video signal.

The electrical characteristics of coaxial cable makes it very suitable for the transmission of the camera to monitor the whole video signal (CCTV video signal is determined by the distribution a wide range of low-frequency signal and high-frequency signal is composed of). Transmission of low-frequency signals (20 Hz to several thousand cycles per second) you can use almost any kind of wire. In practice, nearly all of the wire can be used as a phone line. But you want to transfer the frequency range of 20 Hz to 6 MHz between the video signal, but don't want any attenuation, you need to use a coaxial cable.

In TV monitoring system using video baseband transmission is the most common mode of transport.

The so-called base-band transmission is not subject to any processing, such as the frequency converter and direct transmission of all TV signals. This type of transfer method has the advantage that the transport system is simple; to a certain distance, low distortion; additional low noise (System high signal to noise ratio); having to increase such as modulator, demodulator, additional equipment. The disadvantage is that the transmission distance can not be too far; a video coaxial cable can only transfer one television signal, etc.

Because of this transmission is stable and simple equipment, etc., thus in practice for a wide range of applications.

But the video signal frequency band is wide and starting frequency and very low, so the cable transmission, its amplitude and phase in low frequency and high frequency difference is very big. Particularly in the phase distortion too large, it is difficult to use a simple circuit to compensate. At the same time, the baseband transmission low frequency part very vulnerable to power, telephone, radio, and other low-frequency interference sources of interference.