For microwave signals within the 0.5 to 10.5 GHz range, we present an integrated broadband balun that carries signals from co-axial cable to microstrip to parallel-plate line. We use this arrangement as the feed line for a broadband double-sided antenna, and this antenna feed is presented as an application of the integrated balun. In addition, we devise a testing method for the balun, which is demonstrated. Through this testing method, the transmission, reflection, and radiation losses associated with the balun are readily determined. © 2005 Wiley Periodicals, Inc.