Contents I. Introduction
Space applications in the field of telecommunications are high-speed TV, Internet, telephony, secure aeronautical communications and new technological challenge flexible telecommunications payloads. The use of satellites is omnipresent in society modern, all satellites use electromagnetic waves to link with the earth or to carry out their missions by antennas are the vital components and the main part of this payload system of each satellite [1] –[3]. The antennas are among the most important and critical elements of the satellite. They ensure the transmission of information to a large number of users at a very high level, must be able to reconfigure in flight in order to adapt to user demand and have a very high level of reliability [4] –[6]. Their characteristics directly affect the performance of the system. These antennas are low on highly complex technologies. They can integrate active elements (amplifiers, adaptive filters, converters) and structures In Earth observation, payloads must be capable of performing the functions of an aperture synthesizer, altimeter or atmospheric sounder [7] –[10]. The types of antennas and frequency used are therefore extremely different. In addition, in view of the increase in the use of optical and radar instruments, there is a need to develop transmitting antennae capable of providing a high-level link for transmitting images to terrestrial stations. In order to obtain a sufficient amount of energy (300 Mbits/sec) and be compatible with low-orbit satellites, these antennas will be electronic pointing antennas. Several concepts are conceivable, such as active antennas, switching antennas or remote control devices. Scientific satellites occupy a vast field of exploration of the universe. In the field of radio frequencies, we will find radiometers or radio telescopes. The antennas used are therefore very specific, with problems of their own mainly due to the use of extremely high variations (up to terahertz) [10] –[13].
