A new compact configuration of a printed CPW‐fed semicircular slot antenna with a CPW‐to‐CPW step transition is presented. Its bandwidth is enhanced for ultra‐wideband (UWB) operation by combining linear and stepped CPW‐to‐CPW transitions along the feed line. Its measured 10 dB return loss bandwidth is 3.1–13.8 GHz (126%). This, together with its nearly constant measured gain of 3.5 dBi ± 1 dB from 3 to 10 GHz, makes it suitable for UWB applications. Details of the proposed antenna are described, and both theoretical and experimental results are presented. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2367–2372, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25481