Satellite TV receiving systems mainly include antenna, feedback, high -frequency head, and satellite receiver. The parabola satellite antenna receives the feed signal focused on the front end of the satellite high frequency head, and converted to the C frequency (3.7GHz ~ 4.2GHz) signal or KU frequency band (11.7 ~ 12.75GHz) signal. out. Digital TV signals have a certain anti -error function in transmission. During the transmission, some digitals (ie, error correction codes) are added to the original signal source coding sequence during transmission. To achieve automatic error correction, we can partially deal with random interference and sudden interference during satellite transmission. However, when the receiving TV signal is too interference, it exceeds its fault tolerance range. It will cause adverse effects on the reception of TV signals.
Interference of satellite TV receivering signals of Contents
Common sources of satellite signals
1. Microwave interference
Microwave interference is the culprit that leads to the problem of satellite TV receiving, and is usually the most likely to appear in the C frequency band. The KU frequency band also occasionally occur. Microwave interference can be divided into fixed -frequency interference and radar full -frequency interference, which are briefly described below.
(1) Frequency interference
When the receiving antenna has not yet received the satellite, if many signals that do not belong to the satellite transmission from the spectrum analyzer, and regardless of the turning of the antenna to any direction, these signals will add some specific frequencies. This situation is called it. For frequent interference.
These sources of interference usually come from microwave bases such as military, telecommunications, mobile, etc., and general interference signals are in the C/NF noise to carry noise ratio) ODB 40dB range. Satellite TV programs in the overlap frequency cannot be received normally.
(2) Radar full -frequency interference
Radar full -frequency interference, that is, the entire satellite frequency band is disturbed by the radar, which is difficult to observe from the spectrum analyzer during the antenna setting process.
However, if the SPAN (frequency width) of the spectrum is increased a little, it can be found from the waveform in the cycle every 6 to 12 seconds. The original waveform, this phenomenon is called radar full -frequency interference.
The source of interference usually comes from airport radar and military radar. If the satellite TV signal is received when the satellite TV signal is scanned by the radar wave, the screen will completely stop for 2_3 seconds. As long as the radar is working, this phenomenon will always always be continue.
2. Interference in nature
(1) rain and decay
Refers to the attenuation caused by electromagnetic waves in the rain.
It includes attenuation caused by raindrate absorption and scattering of raindrops. Rain particle absorption attenuation is caused by the medium loss; the attenuation caused by raindropic scatterns is caused by the reflection of the rain keratin when the electromagnetic wave encounters the rain keratin. According to the measured and statistics, the absorption attenuation of raindrates is larger than the scattering attenuation.
(2) Snow decline
Refers to the attenuation of electromagnetic waves in the snow. Dark Snow’s interference with satellite signals is also very large, especially when the satellite antenna parabolus has a lot of snow, which will seriously affect the intensity of the receiving signal and make the TV signal cannot be viewed normally. In addition, the severe weather environment such as thick clouds and hail will have a certain impact on the ups and downs signals of the satellite, and the signal loss generated by different frequencies is different. In short, the attenuation of various hydraulic jets on electromagnetic waves increases with the increase of radio wave frequencies, so the impact on KU bands is much greater than that of the C -band.
(3) The interference and influence of the sun sunspots on the signal of satellite receiving
The sun sunspots will cause huge magnetic storms when they reach the peak. In the process of magnetic storms, a large amount of charged particles were erupted to interfere with the magnetic field of the earth, affecting the ionization layer of the earth, and the normal work of the communication satellite. Every 11.2 Earth Year, the campaign of sun sunspots reaches a peak. When the position of the sun is in the main or sublobes of the satellite antenna, the interference magnetic field will enter the receiving system to affect the normal reception of satellite signals. It is manifested that the signal strength of each channel image sometimes appears at the front end, which will slowly weaken. The black -and -white and miscellaneous waves appear in the screen. The snowflake spots are gradually increased. When the sun sunspots weaken, the satellite TV signal will slowly return to the original strength.
(4) The interference and influence of the signal of the satellite receiving signal
Sun Ling is a natural phenomenon that appears before and after the spring equinox or before and after autumn equinox. During these two solar terms, the trajectory of the Sun Kanzi Movement overlapped the track of the satellite, and the satellite is on the straight line between the sun and the earth (see above). The sun. The sun sunspot produces a strong electromagnetic wave. The electromagnetic wave is a huge source of electromagnetic interference, which will interfere with the satellite signals they receive, which will cause severe deterioration or even interruption of the receiving link, which will cause satellite signals to be interrupted. Essence The length of the duration of Ri Ling is determined by the caliber of the antenna receiving antenna at the Earth Station. The shorter the duration of Ri Ling; otherwise, the smaller the caliber of the antenna, the longer the last time. The peak period of the sun sunspot activity is the most serious; the wider the working frequency band, the more noise received, and the relatively serious interference; the higher the operating frequency, the greater the noise intensity, and the more severe the interference. The degree of interference in Ri Ling is severe than the C frequency band.