Abstract: Characteristics of ultra-wide band (UWB) antenna are studied with end slot-tuned. Based on traditional half-ellipse planar antenna, the impacts of four different tuned slots etched on the antenna end including half ellipse, triangle planar, rectangle planar and sine planar on some antenna characteristics, such as voltage standing wave ratio (VSWR), input impedance, group delay are analyzed. By simulation and analysis, semicircle slot-tuned and resistive-loaded is chosen, and the influence of the number of tuned slots and the distinctive shape of the cavity on antenna performance is analyzed. One novel half-ellipse planar antenna with two half-circle tuned slots and a V-shape cavity operating at a 400 MHz center frequency is designed. This antenna is manufactured and measured. Test results show that the proposed antenna has a large impedance band up to two octaves, high fidelity on time domain waveform. Additionally, this antenna costs low and can be applied in through-wall life detecting radar easily.