October 26, 1995
Abstract -
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.