Communication satellite processing repeaters

Two kinds of processing repeaters which may find application on communication satellites in the near future are described. The type I repeater allows access only if the transmitted signal contains a predetermined code structure. This serves three purposes: first, unauthorized users are excluded, second, co-channel interfering signals are not retransmitted on the downlink, so as not to waste a portion of the satellite transmitter power, and, third, removal of the interference signal at the satellite avoids having to do this at the ground receiving terminal. Thus such a repeater would find particular application where there are a large number of ground receiving stations. The type 2 repeater routes signals received at its N input terminals to be transmitted at N output terminals, thus acting as a "switchboard in the sky." Two purposes are served: first, the satellite capacity is more fully utilized in the presence of fluctuating traffic demands, and, second, single-frequency transmission and reception are possible for user ground stations, thus simplifying these stations and still allowing communication to any station in the network. It is established when the type 1 repeater is able to increase the satellite communication capability beyond that of a simple repeater and further that fairly simple filtering is sufficient on the satellite. For the type 2 repeater, a proposed frequency control plan minimizes the filtering required on the satellite where frequency division multiplex is used and reduces the amount of switching required on the satellite to N single-pole N-throw switches where time division multiplex is used without the requirement of any memory on the satellite. A summary of present-day translating repeaters, as used in the Intelsats III and IV and DSCS II satellites, is included.