Simulation study of DQPSK Intelsat V regenerative/non-regenerative satellite systems

Computer simulations are used to study the performance of a differential quaternary phase shift keying (DQPSK) regenerative/nonregenerative satellite system under various Intelsat V specifications, with attention to performance degradation caused by filter amplitude as well as group delay variations and phase distortions. For DQPSK, the gain resulting from the use of a regenerative satellite repeating system is 2-5 dB, depending on filter characteristics. While filter amplitude variations within the specified Intelsat V masks do not cause significant degradation, the group delay variations cause considerable degradations. The phase error caused by the delay element instability should be kept to less than 6 deg, for a regenerative DQPSK satellite system to sustain a 1-dB performance degradation.