Application of the UWB technology to Wireless Personal Area Network (W-PAN) systems and high-speed wireless Local Area Network (LAN) systems is currently being studied. This paper proposes a thin and compact antenna with very wide band characteristics for UWB systems. Antennas for UWB systems must have good wideband characteristics while being thin and compact because they need to be built into UWB system candidates, such as wireless TVs, hard disk video-recorders, and personal computers. Traditional wideband antennas had to be three dimensional or have a large ground plane, making installation in the above types of equipment difficult. This paper describes the flat-type UWB antenna, which consists of a large elliptical element with a hole, a small elliptical element, and an element shaped like an inverted U, which realizes excellent wideband characteristics. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(12): 54–61, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20301