vsat dish
1 Access network preparation
Firstly, the earth station antenna user should propose the application for Intelsat. Access network earth station user will be informed a week earlier after Intelsat approves and sets access network time and satellite apply, in order that users of access network earth station have enough time to prepare. Thus access network is not in a hurry and unsuccessful so that it doesn’t waste time and opportunity. Before earth station antenna enters Intelsat net, all sorts of factors including station site selection, antenna polarization adjustment and antenna rotation speed, etc. should be taken into consideration.
1.1 Station site selection
The selection of earth station antenna site should be done before antenna installation. It will be likely to have an affect on access network if access network need is not considered. Station site selection usually should comprehensively consider and balance the following factors: I. Geographic condition of station site. II. Interference situation of same frequency and adjacent frequency. III. Condition of climate and environment. IV. Power supply. And geographic condition has great affect on antenna access network measurement. Earth station antenna should possess field of view as large as possible. Generally earth station antenna at least should have protective angle of above 10 degrees in azimuth and elevation. Besides, know whether there are frequency interference of microwave station, radar station and radio station around station site in order to take corresponding measures.
1.2 Adjustment of earth station antenna
The adjustment of earth station satellite communication antenna mainly refers to adjustment of antenna azimuth, elevation, feed focal distance and polarization converter. The formula for calculating theoretical value of antenna azimuth and elevation is as follows:
Az =180+arctg [ ]
El = arctg [
In the formula, is east longitude of on-orbit satellite, is east longitude where earth station antenna is located. is north latitude where earth station antenna is located, R is earth radius(6378km), H is vertical height(35786km) from satellite to the ground.
Azimuth designates due north as 0° and elevation designates the elevation angle when antenna axis reaches horizontal position (relative to the ground) as 0°. Generally International satellite has three beacons with frequency of 3947.5MHz, 3950MHz and 3952.5MHz respectively which can make antenna roughly pointing to satellite according to theoretical value. Using satellite beacon signal and applying spectrum analyzer make antenna accurately pointing to satellite.
After antenna pointing to the satellite accurately, measure antenna rotation speed of the azimuth and elevation because it is required by CSM (collaboration earth station designated by Intelsat) in direction diagram of the access process. The requirement for entering international network is that the rotation speed of earth station antenna is about 0.02 deg/s.
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