A new model for computing the intermodulation signal spectra for a nonlinear amplifier

Intermodulation products can have a significant impact on system performance in any situation in which multiple signals traverse a nonlinear amplifier (e.g., satellite transponders operating into saturation or cellular radio base station amplifiers). This paper presents a new algorithm for determining the intermodulation signal powers and spectra of arbitrary order for any memoryless zonal or IF nonlinear amplifier, given its arbitrary amplitude (or power) and phase characteristics. Introduced as a mathematically based model for a joint occupancy algorithm (JOA), the model´s predictions are most accurate for the case of many input signals. The implementation is much simpler than that of previous approaches; furthermore, the processing task is virtually independent of the number of input signals and the order of the intermodulation signal spectra sought. In this paper, we describe the JOA model, derive the equations employed to evaluate the intermodulation signal powers and spectra, and compare some sample results with the corresponding results computed using more traditional methods. Finally, some limitations of the model are discussed.