Intermodulation in CDMA

Using a soft limiter of the error function type, the authors have applied the time domain Fourier expansion method to analyze intermodulation in multiplexing of CDMA signals. The individual three-tone third-order intermodulation component, normalized with respect to the signal in CDMA, has the same magnitude as that in FDMA except for the reduction by the processing gain. The intermodulation components in FDMA are distributed among all the frequency channels, whereas all the intermodulation components fall on each CDMA channel in a radio carrier band. In practical cases the intermodulation to signal ratio in CDMA is only slightly lower than that in FDMA. However, a CDMA system with digital coding protection and RAKE receiver is expected to need less signal power