vsat dish
In today’s communication, satellite communication is the important component. It possesses characteristics of multi-access ability, flexible network, adaptable to change of business volume and network structure, large coverage, unconstrained by distance and geography. Antenna system is the most unique device of satellite communication earth station, and the input and output channel of radio-frequency signal of earth station. Antenna system of satellite communication earth station includes antenna, feed and servo tracking device.
Antenna system can be applied to transmit and receive electromagnetic wave. The electrical performance is equivalent completely with the features of reciprocity. And the antenna system can bear the work of transmitting and receiving alternately.
The following is the main specifications of antenna system performance.
First of all, it is antenna gain. It describes antenna’s radiation intensity, which depends on antenna efficiency. The antenna efficiency should be improved as far as possible in the design to obtain the maximum gain. In the project it adopts and uses high-efficiency feed, and modifies prime and sub-surface shape, in order to improve efficiency.
Secondly, antenna noise temperature must be low.
Moreover, it is antenna directivity. The directivity means the intensity of antenna radiation field in some direction in space. Different occasions have different requirements for antenna directivity. For example, mobile communication antenna is omni directional in horizontal plane and it can communicate no matter which direction it is. However, the directivity of parabolic antenna for satellite communication is quite sharp, which usually refers to its service region. Thus it makes energy concentrated and efficient. Moreover，satellite orbit space must be narrowed because satellite arrangement in geostationary satellite orbit is quite crowded. And thus it will cause the problem of mutual interference between earth station antenna and adjacent satellites. To make full use of satellite orbit resource and reduce the interference of earth station antenna on other satellites which operates at the same band, the directional technical specification of earth station antenna becomes particularly important.
Lastly, it is antenna polarization which refers to oscillation direction where antenna radiates or receives electric vector in electromagnetic wave. The common polarization form of electromagnetic wave has three types which are vertical polarization, horizontal polarization, and circular polarization. The base station antenna of mobile phone and pagers adopts vertical polarization. For example, mobile antenna should be placed vertically when communicating by mobile phone. Thus, as for critical distance communication, the communication quality will be obviously improved.
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