TABLE OF CONTENTS Communication satellites are very much a part of EW. Systems talk to each other over satellite links, and hostile satellite links are logical targets for intercept or jamming. Communication satellites carry information between terminals on or near the surface of the Earth as shown in Figure 7.1. Link equations are defined for the uplink, the downlink, and the whole path between the terminals. Although satellite links use the same laws of physics as ground-to-ground or air-to-ground communication, they are typically designed and described using different formulas. The differences result from the nature of the space environment and from the way that communication satellites are used.
A basic assumption used in the normal EW equations (applied within the atmosphere) is that all of the equipment and the transmission medium is at 290K. This works because the kelvin scale goes down to absolute zero and a temperature change adequate to cause 1 dB of change in the link in either direction is way more than that which causes humans to die. However, in space, very low temperatures (near absolute zero) are common. This requires a different way of looking at receiver sensitivity.
Communication satellite links typically have a great deal of bandwidth to serve multiple, simultaneous users, each of which buys only the amount of bandwidth required. This makes link equations in...
