Frame synchronization technique for satellite on-board switching systems

Claim 1

A satellite communications system of the type comprising a plurality of earth stations adapted to transmit signals to one another via a satellite relay transponder, the improvement comprising, a. a plurality of receiver means on said satellite directed to receive signals transmitted toward said satellite from earth stations located in a plurality of zones, respectively, on said earth, b. a like plurality of transmitter means on said satellite directed to transmit signals toward earth stations located in a plurality of zones, respectively, on said earth, c. interconnection means for interconnecting said plurality of receiver means with selected transmitter means to complete communication paths between selected zones on said earth during each of several brief time intervals of a recurring time division multiplex frame period, a particular connection between one receiver means and one transmitter means forming a communication path between earth stations in the respective zones of said one receiver means and said one transmitter means, d. frame control means on said satellite for causing said interconnection means to periodically interconnect for a brief time, less than said time division multiplex frame period, each receiver means with the respective transmitter means serving the same zone, whereby during said brief time of each said period closed loops are formed between each zone and said satellite to cause signals received from any zone to be transmitted back to said zone, and e. pattern control means operating at the same periodic rate as said frame control means for controlling said interconnecting means to cause interconnections during the remainder of each said period in accordance with a prearranged pattern.