This paper presents the emergence of reconfigurable antenna for the developments in wireless technology. The proposed work deals with the design of low-profile, reconfigurable, tunable multiband patch antenna for different types of wireless applications such as Wi-Fi, Wi-max, Bluetooth ,3G within a microwave L, S, C, and X frequency bands in Electromagnetic Spectrum, cognitive radio applications. Today, different antennas are preferred for different wireless applications. The major issues are increased complexity and the size of the devices. By using proposed technique, the selection of different frequency band in communication systems can be conveniently served by only one antenna. The proposed antenna consists of rectangular patch designed with U-shape slot with three RF PIN diodes placed at different position on the ground plane to achieve frequency reconfigurability i. e. to select different frequency band depending upon wireless applications.The analysis are performed using Agilent Advanced Design System software. The main advantage of this design is that the proposed antenna is having low profile, light weight, and easy to fabricate.