vsat dish
Earth station antenna basic function is that RF signal from the transmitter becomes electromagnetic wave which orient point to the Satellite and radiate, while the antenna will transfer the weak energy of electromagnetic wave from Satellite to high-frequency signals efficiently and sent to receiving equipment. Usually the earth station antenna has the features of high gain, low side lobes, strong radiation and low noise. The antenna main specification is the antenna gain, antenna radiation pattern, beam width, side lobe, noise temperature and Polarization…etc.
1. Earth station antenna system
Reflector antenna is adopted in most earth stations, electric wave is reflected once or many times and radiate to the space. The main body of the antenna is made of main reflector and primary radiator, sometimes sub-reflector. Normal reflector antenna has the types of horn reflector antenna, Cassegrain antenna, offset antenna and ring focus antenna…etc.
2. Earth station antenna feed system
Earth station antenna feed system include horn, polarizer, OMT…etc., which realize the exchange between high-frequency power and electromagnetic wave and use one antenna to transmit and receive. The main function of antenna feed system: the ability of radiating electromagnetic wave; separate and compose the signal polarization in dual polarization system; isolate the receiving and transmitting signal frequency; supply the error signal to some Satellite tracking system.
3. Earth station antenna servo system
Earth station antenna servo system function: according to the command requirements control the antenna to rotate steady. Servo system mainly include the antenna servo controller and servo motor, in order to avoid the motors can’t be stopped to make the servo broken under unforeseen circumstances, set up a limit switch on the limit position where the antenna is collected or opened. When the antenna travel at the limit position, limit switch cut off the motor driver and the power supply force the motor to stop, at the same time the status of limit switch can touch limit warming, remind the operator to handle it properly.
4. Earth station antenna tracking system
Synchronous satellites drift every day like “8”, but antenna beam width of the medium and large earth stations is narrow. In order to realize the tracking for the Satellite, in the Satellite communication earth station the antenna tracking system is established specially, mainly include tracking receiver and corresponding automatic tracking device, the control mode has manual tracking, programmed tracking guided by computer, step tracking and monopulse tracking.
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