9.6 Earth Station Facility Design

The last practical consideration to be covered is the physical installation of the Earth station, that is, the design of the building and the arrangement of equipment therein. It is instructive to take as an example the layout of the site and building for a major Earth station, shown in Figure 9.17. Many of the same principles can be applied to smaller stations, including VSATs. The drawing assumes operation with GEO satellites with the station located north of the equator. Consequently, the antennas are aligned along the southern perimeter of the site to afford good visibility of the orbit arc. This arrangement of the antennas is usually the most flexible if there is sufficient space between the reflectors to allow independent pointing of each main beam to any orbit position. Care in placing the foundations must be taken so that antennas never touch each other during repointing and that the beams do not overlap one another to a significant degree. The latter minimizes the interaction of the electromagnetic fields around the antennas, including the effects of diffraction. With proper isolation between antennas, the beams will be properly formed, giving the desired cross-polarization isolation and contol of sidelobes.

Figure 9.17: Site plan and equipment arrangement for a typical major Earth station.

The next important aspect is the location and arrangement of the RF equipment. The LNAs or LNBs should be mounted directly on the receive port of the feedhorn to minimize noise and loss. That also...