TABLE OF CONTENTS The performance requirements of the Earth station mirror those of the satellite. That is to ensure that there is a satisfactory RF link between the ground and the space segments under all expected conditions and for the range of required services. In addition, the Earth station determines the baseband quality and much of the end-to-end communication performance of the services being provided. We first consider the key parameters of EIRP and G/T as they relate to the ground.
The Earth station EIRP simply is the value that applies to the uplink. As with the satellite (downlink) EIRP, it is obtained by multiplying the antenna gain (as a ratio) by the transmit power at the input to the antenna. In decibel terms, it is the antenna gain plus the transmit power in decibels relative to 1W (dBW). As shown in simplified block diagram in Figure 9.2, the EIRP also considers any RF loss between the HPA and the antenna. The loss factor, l t, is a number greater than 1, and the ratio 1/ l t is actually the transmission factor (e.g., a gain less than 1). Major Earth stations typically are designed for reliable uplink operation with low outage due to rainfall. Therefore, the required uplink EIRP is substantially higher than that of the downlink (possibly including uplink power control). That may require the use of vacuum tube HPAs capable of transmitting several kilowatts or at least a substantial fraction of 1...
