Antenna configuration and modelling: The antenna configuration is
shown in Fig. 1. It is a single square patch antenna with two PIN
diodes embedded on each edge of the patch. The PIN diodes are
arranged, as shown in Fig. 1, so that the beam direction can be
switched to x- and y-direction by applying forward and reverse bias,
respectively. The patch size is 1/2 at the frequency 2.44 GHz.