An improvement of nonlinear characteristics in DS-SSMA communication systems using equalizers

This paper proposes an improvement method of the deteriorated characteristics on account of the nonlinearity in direct sequence spread spectrum multiple access (DS-SSMA) communication systems. Where, a traveling wave tube (TWT) is adopted as nonlinear circuit in which the amplitude nonlinearity and AM/PM conversion are assumed to be relatively small. The transmission signal is expressed in two quadrature components and an equalizer of feed-forward transversal type is used to improve the nonlinear characteristics. The calculation results show that the significant improvement can be obtained from a simple equalizer using the least mean square algorithm