THE FEATURES OF MULTIBEAM SATELLITE-COMMUNICATIONS SYSTEMS EMPLOYING SIGNAL SWITCHING

One of the important advantages of satellite communications systems is their global nature, although therein also lies a drawback: in the large majority of cases, the radiated signal is needed at a single point on the earth's surface, while the power from the satellite transmitter is radiated over the entire zone illuminated by the satellite antenna. The unused power losses from the satellite transmitter are greater, the larger the illuminated zone. This drawback is particularly serious in fixed communications service were the position of the ground stations is known in advance and on which high carrying capacity requirements are imposed. Multibeam antennas have recently been employed more extensively [1-3] on satellite repeaters (RPT) to reduce the zone of useless transmitter power scattering. Their application has had two positive effects: first, the required signal energy radiated by the repeater and directed to the single station is reduced, which extends the threshold of the power limit on the carrying capacity of the repeater and, in the final analysis, makes possible communications with small inexpensive stations. Second, it permits multiple use of working frequencies (on different beams), which extends the threshold of the frequency limit on the carrying capacity. The price of these advantages in addition to more complex antennas includes the need to incorporate signal switching in the repeater to establish communications between subscribers located in zones illuminated by different beams.