Operating principle and design approach of a novel dual-band aperture-dipole composite antenna are proposed. It is shown that multiple operating modes can be simultaneously excited by employing offset-feeding technique at first. After the behavior of each mode is studied, the operating principle of the antenna is analyzed and described. Then, an improved dual-band aperture-dipole composite antenna is formed and it is designed by using the proposed approach. The antenna is experimentally verified. It is demonstrated that two operating bands for radiation are ranged from 2.36 to 2.58 GHz and from 4.1 to 15.72 GHz, respectively, in which the reflection coefficient are both © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:382-393, 2015. © 2014 Wiley Periodicals, Inc.