What is a Satellite Ground Station? What is Its Function?
Any satellite communication line includes transmitting and receiving ground stations, uplink and downlink, and communication satellite transponders. The basic function of the ground station is to transmit signals to the satellites, and at the same time receive the signals retransmitted by the satellites from other ground stations. The ground stations for various purposes are slightly different, but the basic facilities are the same.
What Are the Characteristics of Radio and Television Satellites?
Digital satellite television is a form of broadcast television that uses geostationary satellites to transmit digitally encoded and compressed television signals to users.
There are mainly two ways. One is to transmit the digital TV signal to the front end of the cable TV, and then the cable station converts it into an analog TV and transmits it to the user's home. At present, cities mainly use this method.
Another way is to transmit the digital TV signal directly to the user's home. In this way, the satellite has high transmit power and can be received by a smaller antenna, which can be used by ordinary families.
Do Radio and Television Satellite Ground Stations Emit Electromagnetic Waves?
Any satellite ground station communicates with the satellite through wireless electromagnetic waves. The broadcast satellite receiving antennas that we can usually see on the roofs of offices, residences, hotels, etc. are used to receive broadcast signals from satellites. This equipment is only used to receive electromagnetic waves from satellites. The principle is the same as that of the home. The radio is the same, but the signal from the satellite is too weak, and a special parabolic antenna must be used to receive the signal in a concentrated manner to obtain an effective signal. The larger the antenna, the better the received signal. Therefore, this kind of satellite ground station external No electromagnetic wave radiation.
Another type of satellite ground station used by the broadcasting and television department is to process the completed program, send it to a synchronous satellite, and then forward it to other places through the satellite. This kind of satellite ground station has electromagnetic wave radiation to the outside world. .
Is the Electromagnetic Radiation of Radio and Television Satellite Ground Stations Large?
The satellite ground station communication uses a parabolic microwave antenna. The principle of microwave antenna is similar to that of optical astronomical telescope. When the antenna is used for transmission, electromagnetic energy is radiated outward from the center point of the phase of the horn, and is radiated to the sub-reflector in the form of a spherical surface. After being intercepted by the sub-reflector, it is emitted to the main reflector. Above, it is corrected to plane wave so that the energy is more concentrated and emitted.
Similar to the principle of reversibility of the optical path in optical devices, the "path" of the microwave electromagnetic wave emission and reception is reversible, that is, the emission characteristics of the antenna are consistent with the reception characteristics. The directivity of the antenna is very high, and its electromagnetic waves are concentrated in a very narrow area in front of the antenna. Generally, the "antenna gain" is used to measure the concentration of electromagnetic waves. The antennas used in satellite ground stations have electromagnetic waves concentrated in the main lobe area. , which accounts for the vast majority of the total radiated electromagnetic energy, and the rest of the electromagnetic waves are rarely leaked.