Page 268 - Satellite Communications, Fourth Edition

248 Chapter Eight

Figure 8.6 More detailed block diagram of a transmit-receive earth station.

through a diplexer, which allows the antenna to handle transmit and
receive signals simultaneously.
The station’s antenna functions in both, the transmit and receive
modes, but at different frequencies. In the C band, the nominal uplink,
or transmit, frequency is 6 GHz and the downlink, or receive, frequency
is nominally 4 GHz. In the Ku band, the uplink frequency is nominally
14 GHz, and the downlink, 12 GHz. High-gain antennas are employed
in both bands, which also means narrow antenna beams. A narrow beam
is necessary to prevent interference between neighboring satellite links.
In the case of C band, interference to and from terrestrial microwave