Pattern and polarization reconfigurable circular patch for MIMO systems

In this paper we present a novel design for a reconfigurable circular patch antenna (RCPA) that exploits both pattern and polarization diversity to deliver high gains in multiple input multiple output (MIMO) communication systems with respect to standard non reconfigurable arrays. The antenna consists of a circular patch whose radius can be reconfigured to change the shape of the excited radiation pattern. Perturbation segments are connected or disconnected from the inner circular patch through PIN diodes to dynamically change the antenna polarization state. To diminish the antenna space occupation on the communication device two feed points are located on the same antenna structure such as a single antenna acts as a two element array. The gains offered by the antenna have been determined through field measurements in an indoor environment, using channel capacity as performance metric. Employing the proposed antenna in a 2times2 802.11n MIMO system, we measured on average a percentage capacity improvement of 26% with respect to non reconfigurable circular patches that works with the electromagnetic mode TM₂₁.