Overlay cognitive radio is described in this paper. Channel activity is endlessly guide by the Wide band sensing antenna and a reconfigurable filtenna need to change the performing frequency. MIMO antenna system is considered to reduce multipath fading and to improve channel capacity. MIMO reconfigurable filtenna is designed and simulated using HFSS software. Sensing antenna covers the frequency range 3–10 GHz and reconfigurable filtenna used to transform wideband response to narrowband which is suitable for cognitive radio system.