This paper describes a compact size UWB rectangular planner monopole antenna with impedance band from 7.6-15 GHz, having gain of 5.94 dBi which act like a sensing antenna for CR. After that, a filter structure is implemented at feed line of the monopole antenna with Incorporation of reconfigurable elements(switches) to make the antenna reconfigurable. By operating the switches as ON or OFF, the UWB antenna now operated at different frequencies like 8.7 GHz, 9 GHz and 11.4 GHz with narrowband functionality. This condition is helpful to CR for communication in desired band.