A DIVERSITY SCHEME FOR A PHASE-COHERENT FREQUENCY-HOPPING SPREAD-SPECTRUM SYSTEM

Frequency diversity for a phase-coherent frequency-hopping spread-spec trum system is proposed. The frequency band of the communicator is par titioned into L disjoint subbands on which L replicas of the communica tor signal are simultaneously transmitted; each signal replica hops in dependently in its subband. Therefore, both phase continuity and coher ent optimal combining of the received replicas are possible. Optimum d iversity is thus at least 6 dB better than the conventional noncoheren t FH-SS system, We show that a smart jammer should be present in all s ubbands. We also give a sufficient condition that forces the jammer to spread its intereference signal on the whole communicator frequency b and.