Abstract-This paper presents a new rectangle-slot antenna for ultra wideband applications with 3.5/5.5 GHz dual stop-band characteristics. The antenna contains a simple square radiating patch and a rectangle-slot ground plane, which provides a wide bandwidth from 2.6 GHz up to 14.1 GHz. In order to obtain dual stop-band properties at 3.5 and 5.5 GHz, a rectangular-shaped slot is etched off the ground plane, and a strip line ended up a shorting pin is applied, respectively. The antenna is simple in configuration and has a compact dimension of 20×22 mm 2 . The proposed antenna is designed, simulated and fabricated. The measured results exhibit a acceptable agreement with the simulated data. The antenna provides nearly omnidirectional radiation patterns, relatively flat gain over the entire UWB frequency excluding the two stop bands.