A compact antenna with extended band-notched characteristics was designed for ultra wideband (UWB) communications. The antenna consists of a crescent-shaped elliptical patch with a T-shaped stub and a square ground board plane. The antenna is easily integrated with radio-frequency/microwave circuits to reduce the manufacturing cost. The central frequency and the notch bandwidth can be adjusted by changing the size of the T-shaped stub. Simulations verify the design characteristics. Measurements show that the antenna produces the UWB working bandwidth.