Wide band switchable circularly polarized microstrip antenna using double-balanced multiplier

In this paper, the reconfigurable antenna which excites orthogonal a circular polarization is proposed and the behavior and the characteristics of the antenna are experimentaly investigated. The proposed antenna has the cross slot at the center of the patch, and four diodes are embedded in a star form across the slot. A circular polarization is excited though in a wide band due to the nonlinearity of the diodes. When the bias voltage V_c superimposed on the RF signal is a slighty positive near 0 V, a LHCP is achieved. On the other hand, when V_c is a slightly negative near 0 V, a RHCP is achieved. Therefore, it is easily possible to switch the phase difference of plusmn90 degrees by a bias voltage V_c for those diodes in a wide band. As a result, switchable circular polarization antennas can be achieved in a wide frequency band. The proposed antennas are practically attractive for the wireless communications as a circularly polarized active antenna.