A Reconfigurable Patch Antenna with Controllable Polarization Sense and Beam Direction

It is well known that directional antennas and circular polarization (CP) antennas are effective in reducing degradations of receiving power caused by multipath propagation effects [1]. Therefore, simultaneous controlling these two features—directivity and polarization—is expected to considerably reduce such adverse effects. Some papers have reported CP antennas with beam steering means [2], [3]. In those antennas, their main beams are tilted from their bore sight and Axial Ratios (AR) of their main beam directions are less than 3 dB. However, their polarizations were still fixed. In contrast, choosing their polarizations so as to avoid the detrimental fading loss caused by multipath propagation has been also reported in [4] and [5]. In those antennas, right-hand CP (RHCP) and left-hand CP (LHCP) can be switched with respect to phasing conditions. Although, their main beam directions were fixed. This paper presents a novel reconfigurable antenna, which is able to control both polarization sense and main beam direction. Four slots are introduced in the ground plane of a conventional patch antenna to excite the CP mode and tilt the main beam direction of the antenna. And we demonstrate that polarization sense and main beam direction of the antenna are controlled by switching PIN diodes mounted across the slot.