Accurate multisine representation of digital communication signals for characterization of nonlinear circuits

A technique for generating an accurate multisine representation of a digitally modulated signal using discrete fast Fourier (DFT) coefficients is presented in this paper. A reverse link IS-95 signal containing 200 symbols is modeled by a 240 tone multisine signal where the amplitude and phase of each tone is defined by the truncated Fourier coefficients of the original signal. Adjacent-channel power ratio (ACPR) and error vector magnitude (EVM) measurements of the multisine signal applied to a nonlinear amplifier are in excellent agreement with measurements using the IS-95 reverse link signal. This work demonstrates the accurate use of multisine signals obtained from Fourier coefficients to represent time-domain signals for analysis and measurement of nonlinear circuits.