Satellite antenna

Satellite antenna is nothing much different from the dish antenna which is used on the ground for receiving the signals in the form of microwaves from communication satellites. Though there is no fundamental difference between the two, there is a significant difference in the type of material being used for each. This is because both are used in different environments. Thus the design requirements that have to be taken into account are totally different. The space conditions are harsh and hence the satellite antennas have to be built to withstand such difficult conditions.
The material chosen for satellite antenna constructions have to be carefully picked. The temperatures variation is very large in space. The light and the dark see extreme temperatures and this result in expansion and contraction of the material. Thus a significant amount of resources are used to choose the material only. Also the directivity and the gain of the satellite antenna are designed to suit its specific need. Also the altitudes of the satellite play a significant role in determining the gain of the antenna.
The satellite antennas only occupy approximately two to three meters of the space on the satellite. However, the altitude and direction of the antenna have to be carefully monitored so that the desired gain and directivity is obtained. For e.g. the satellites in the lower earth orbit are using less directive antennas because the signals are received and transmitted from Earth are over a wider angle. Thus the signal direction changes as the satellite changes its position. This is the reason why low earth orbit satellites do not use a parabolic reflector often.
However the functioning of the satellite antenna is similar to the ground antenna. It has a low noise block converter LNB. The Low Noise Block converter performs dual function. It first receives the reflected waves from the antenna and amplifies it. Secondly, it converts the signals to such a high frequency that even after the loss introduced by the coaxial feeder over the feeder length, the signals received by the sets is strong. This is thus a major unit of the antenna as in its absence the signals received at the sets would be very weak.
In the satellite antenna, the gain obtained in the transmission is proportional to the circular aperture of the antenna and the wavelength of the transmitted signals. The gain achieved is given by the formula:
G=
Where G is the gain
D is the reflector diameter in same unit as wavelength
? is the wavelength of the signal
Thus, in the designing of the satellite antenna, the selectivity of the material, the directivity and the gain have to be considered.