October 26, 1995
This discussion addresses the issues of modeling, analysis, and simulation in a mobile satellite communication system. The proposed architecture of such systems is first presented. The system uses an antenna array where each beam, or cell, is defined by a precise amplitude and phase excitation of all or some of the antenna feed elements. The proposed architecture uses a bank of butler matrices between the High Power Amplifiers and the antenna feed elements. We show that this serves to increase the uniformity of loading among the Amplifiers as well as to spatially distribute the energy in InterModulation (IM) products. Analytical models for these components are presented. We then address the specific effect of spatial dispersion of Intermodulation power generated by the nonlinear characteristics of the High Power Amplifiers. A computationally efficient method for quantifying the effective increase in signal to IM power ratio due to this spatial dispersion is discussed. This method relies on the fact that IM power is due primarily to third-order effects, and makes use of combinatorial methods.