Uniform circular arrays: The key to optimum channel capacity in mobile MIMO satellite links

In this paper, we investigate the benefits of uniform circular arrays (UCAs) as an alternative antenna deployment to uniform linear arrays (ULA), which are commonly applied for multiple-input multiple-output (MIMO) systems. We consider a MIMO satellite link with focus on the Line-of-Sight (LOS) signal component of the MIMO channel between two geostationary satellites and a mobile earth terminal equipped with several antennae. The MIMO LOS channel is optimized with respect to the maximum achievable spectral efficiency. The aim of our approach is to keep this optimum spectral efficiency nearly constantly even if the terminal on earth is moving. We provide an analytical derivation for the optimum UCA arrangement and prove our results by numerical simulations. Especially for mobile applications, the UCA antenna arrangement seems to be a reasonable candidate in order to guarantee high capacity performance durably. To this end, we present a very simple triangle shaped antenna arrangement which is compact enough to allow vehicle roof top installations for S-band applications.