  In this paper, we propose a full-rate full-diversity space-time block code
(STBC) for 2x2 reconfigurable multiple-input multiple-output (MIMO) systems
that require a low complexity maximum likelihood (ML) detector. We consider a
transmitter equipped with a linear antenna array where each antenna element can
be independently configured to create a directive radiation pattern toward a
selected direction. This property of transmit antennas allow us to increase the
data rate of the system, while reducing the computational complexity of the
receiver. The proposed STBC achieves a coding rate of two in a 2x2 MIMO system
and can be decoded via an ML detector with a complexity of order M, where M is
the cardinality of the transmitted symbol constellation. Our simulations
demonstrate the efficiency of the proposed code compared to existing STBCs in
the literature.
