 
Summary: Antenna Saturation Effects on MIMO Capacity
T. S. Pollock, T. D. Abhayapala, and R. A. Kennedy
National ICT Australia
Research School of Information Sciences and Engineering
The Australian National University, ACT 0200, Australia
Email: tony.pollock@anu.edu.au
Abstract A theoretically derived antenna saturation point
is shown to exist for MIMO systems, at which the system
suffers a capacity growth decrease from linear to logarithmic
with increasing antenna numbers. We show this saturation point
increases linearly with the radius of the region containing the
receiver antennas and is independent of the number of antennas.
Using an alternative formulation of capacity for MIMO systems
we derive a closed form capacity expression which uses the
physics of signal propagation combined with statistics of the
scattering environment. This expression gives the capacity of a
MIMO system in terms of antenna placement and scattering
environment and shows that the saturation effect is due to spatial
correlation between receiver antennas.
I. INTRODUCTION
