Abstract: A design method of broadband antennas based on the concept of multi-mode filters is proposed. The multi-mode broadband filters have been researched for many years. In fact, the radiation element of a resonant antenna is also a resonator, and also has multiple modes. Therefore, the concept and design method of multi-mode filters can be applied to design broadband resonant antennas. In this paper, the principle of multi-mode broadband antennas is presented, and the typical design method is demonstrated by stub-loaded dipole. The simulation and measurement results show that the bandwidths of the designed antennas are enhanced with the same sizes.