An analysis of nonlinear distortion due to TWT in asynchronous DS-SSMB communication systems

We analyze the effects of the amplitude nonlinearity and AM/PM conversion in a traveling wave tube (TWT) used in an asynchronous direct sequence spread spectrum multiple access (DS-SSMA) communication system, assuming that the nonlinearity is represented by the power series of the input signal and the conversion is relatively small. We propose an analytical method of the signal-to-noise ratio at the output of the correlation detector in the receiver. We also justify our method by comparing the theoretic results with the computer simulations in when the amplitude nonlinear circuit is modeled by an error function as a typical example and show that the third order intermodulation product can be almost neglected in the sense of the signal-to-noise ratio.<>