In this article, a time domain method for designing microstrip-line ultra wideband passband filters is presented.From the filter expected specifications, the profile of the nonuniform transmission line is calculated analytically. The filter presented in this article illustrates the proposed method and emphasizes its potential. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1006-1011, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25921