Fifth-order nonlinear distortion analysis of forward-link CDMA signals

Explicit and closed-form analytical expressions relating the spectral regrowth of the forward-link code division multiple access (CDMA) signal passed through a nonlinear amplifier to both the third-order intercept point and fifth-order intercept point, IP₃ and IP₅, are derived based on a time domain model which is used to derive the power spectrum density and other statistical properties of the CDMA signal. Using the power series and high-order cumulant theory, we obtain an expression for the autocorrelation function of the output signal as a function of the statistics of the input signal transformed by a behavioral model of the amplifier. After the Fourier transform and integral, the expected expression is given. In the end, the comparison between the simulation and practical measurement shows that using both IP₃ and IP₅ is better than using only IP₃.