A compact of a reconfigurable rectangular microstrip slot patch antenna of operat- ing frequencies in the range of (2–6) GHz is proposed for Wireless Local Area Network (WLAN) applications. It has one port excited with microstrip line feed mechanism. The proposed antenna consists of a single layer patch antenna with two parallel slots designed that can be controlled via two switches. Two parallel slots are incorporated to perturb the surface current path, introduc- ing local inductive effect that is responsible for the excitation of the second resonant mode. By adjusting the status of the switches state either on or off mode in simultaneously, the resonance frequencies can be varied, thus achieving frequency reconfigurable. I represent a fully information and design for reconfigurable antenna to use it in a new hybrid device known Cognitive Radio CR. A cognitive radio CR is a wireless transponder that can sense the environment in which it wishes to operate and can adapt itself to optimize its operation. Sensing the environment may involve the measurement of the communications traffic and inter- ference across a large part of the electromagnetic spectrum. The radio will also have knowledge of the intentions of its user, to enable it to match its searches to the needs of the user. In simple words the operations consist of Sensing and Reconfigurability called a Cognitive Radio CR.