Effects of nonlinear distortion on CDMA communication systems

We report a rigorous approach to analyze the effects of nonlinear distortion on code division multiple access (CDMA) wireless communication systems based on time-domain analysis and band-pass nonlinearity theory. Given AM-AM and AM-PM characteristics of a nonlinear device, this technique is capable of predicting adjacent channel power rejection (ACPR), noise power ratio (NPR), two-tone intermodulation products, CDMA waveform quality, and baseband signal vector constellation at the output of the nonlinear device. To demonstrate and verify the capability of this technique, an L-band power amplifier was designed, built, tested with CDMA waveforms, and compared with the simulated results. Excellent agreement between the measured and predicted results has been achieved.