A Dual-Linearly-Polarized MEMS-Reconfigurable Antenna for Narrowband MIMO Communication Systems

The design and characterization is described of a compact dual-linearly-polarized reconfigurable 2-port antenna. The antenna can operate in two different selectable linear polarization bases, thus being capable of reconfiguring/rotating its polarization base from vertical/horizontal (0 degrees/90 degrees), to slant +/- 45 degrees. The antenna has been implemented on a Quartz substrate, and uses monolithically integrated micro-electromechanical (MEM) switches to select between the two aforementioned polarization bases. The antenna operates at 3.8 GHz and presents a fractional bandwidth of 1.7%. The interest of the proposed antenna is two-fold. First, in LOS scenarios, the antenna enables polarization tracking in polarization-sensitive communication schemes. Second, there are the gains of using it in a multiple-input multiple-output (MIMO) communication system employing orthogonal space-time block codes (OSTBC) to improve the diversity order/gain of the system in NLOS conditions. These benefits were verified through channel measurements conducted in LOS and NLOS propagation scenarios. Despite the simplicity of the antenna, the achievable polarization matching gains (in LOS scenarios) and diversity gains (in NLOS scenarios) are remarkable. These gains come at no expenses of introducing additional receive ports to the system (increasing the number of Radio-Frequency (RF) transceivers), rather as a result of the reconfigurable capabilities of the proposed antenna.