TABLE OF CONTENTS Frequency slots may be preassigned to analog and digital signals, and to illustrate the method, analog signals in the FDM/FM/FDMA format will be considered first. As the acronyms indicate, the signals are frequency-division multiplexed, frequency modulated (FM), with FDMA to the satellite. In Chap. 9, FDM/FM signals are discussed. It will be recalled that the voice-frequency (telephone) signals are first SSBSC amplitude modulated onto voice carriers in order to generate the single sidebands needed for the FDM. For the purpose of illustration, each earth station will be assumed to transmit a 60-channel supergroup. Each 60-channel supergroup is then frequency modulated onto a carrier which is then upconverted to a frequency in the satellite uplink band.
Figure 14.2 shows the situation for three earth stations: one in Ottawa, one in New York, and one in London. All three earth stations access a single satellite transponder channel simultaneously, and each communicates with both of the others. Thus it is assumed that the satellite receive and transmit antenna beams are global, encompassing all three earth stations. Each earth station transmits one uplink carrier modulated with a 60-channel supergroup and receives two similar downlink carriers.
The earth station at New York is shown in more detail. One transmit chain is used, and this carries telephone traffic for both Ottawa and London. On the receive side, two receive chains must be provided,...
