Spatial Diversity Performance of Multiport Antennas in the Presence of a Butler Network

The main concern of this paper is to study the presence of a cascaded Butler network in diversity antenna systems. The advantages of a cascaded Butler network in 2-D multipath environments have been already shown. These advantages are limited to either correlated or nonuniform multipath environments with a line-of-sight component. In the frame of this paper, for the first time, we show a further advantage of a cascaded Butler network in 3-D multipath environments, including the effects of coupling. This advantage is associated with an improved convergence in received signals' covariance matrix in a multipath environment wherein the number of independent incoming waves is limited, i.e., nonrich multipath environment. For this purpose, we use a simulation tool in which a multipath scenario with certain number of incoming waves is emulated and some selected multiport antennas are exposed to it. Afterwards, the simulated random received signals are used to yield different performance metrics like spatial correlation. This advantage achieves considerable practical interest since a typical actual multipath scenario is most likely a nonrich multipath environment.