A compact size slot antenna designed for ultrawideband (UWB) applications is proposed.The slot embedded into the antenna was comprised an open‐ended hemicircular slot and a narrow rectangular slot. To achieve good impedance matching within the desired band of interest, the 50 Ω microstrip feed‐line is loaded with an elliptical slot, while an extended substrate was protruded above the upper edge of the antenna. The experimental results such as return losses, radiation patterns, and gain properties are studied, and good characteristics are demonstrated. Typical frequency domain responses are also measured to ensure that the proposed antenna can provide stable signal transmission within the UWB spectrum. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:86–91, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26514