Analysis of MIMO capacity in waveguide environments using practical antenna structures for selective mode excitation

Different realistic antenna configurations are studied and their impact on MIMO capacity is investigated in waveguide-like environments, such as hallways, tunnels or streets. Simulations are conducted for a 2×2 MIMO system using the the finite element method, which is particularly well suited for this kind of problem. First, each antenna is optimized independently from the other by optimizing its shape and location in a manner that insures optimal input impedance and excitation of a single mode. Subsequently, the two antennas are placed together and a final optimization is carried out to reduce their mutual coupling and improve the impedance matching. The results obtained for a 2×2 MIMO system clearly show the significance of practical antenna considerations on MIMO capacity in a waveguide environment.