This paper describes the design and validation by simulation of compact dual-port reconfigurable antennas (via switches) providing antenna diversity or port duplexing, which in turn are useful in advanced techniques such as cognitive radio (CR) and Multiple-Input Multiple-Output (MIMO). The design results from optimization of an initial structure using the Genetic Algorithm (GA) and evaluated via Method of Moments (MoM) electromagnetic simulation. The optimization process determines concurrently: antenna geometry, location, number and state of the switching devices. The starting point is a simple planar antenna that offers robustness, compactness and allows for an easy fabrication. The resulting devices operate over a band of 0.6 octaves and possess dimensions under 0.25λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.25λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> for the lowest frequency of operation.