Performance improvement of CDMA/QPSK systems with nonlinear channel using decision feedback equalizers

This paper proposes an improvement method of the performance characteristics of a quadriphase phase-shift-keyed code-division multiple-access (CDMA/QPSK) system with a nonlinear channel such as a satellite repeater which consists of a traveling-wave tube (TWT). Two adaptive decision feedback equalizers are used to improve the system performance degraded by the nonlinear channel. From calculation results, it is shown that the degradations are improved considerably.