INTRODUCTION TO COMMUNICATIONS SATELLITES.

The use of communications satellites to transmit voice, data, and television programming is revolutionizing business and home entertainment services. Presented are basic operational principles: what a communications satellite is and how it works. Current issues such as reduced orbital spacing to relieve the shortage of orbital slots is also covered. As with any new technology, the state-of-the-art is steadily advancing. The introduction of solid-state power amplifiers (SSPAs) to replace traveling-wave-tube amplifiers (TWTAs) is considered, thus increasing the traffic capacity and the reliability of communications satellites. Some of the benefits of SSPAs versus TWTAs are described. Direct Broadcast Satellites, the latest innovative application of microwave technology, are examined that use high-power TWTAs to transmit television programming directly from the satellite to low-noise home receivers.