Utilization of Both Odd and Even Modes for Multi-band Dipole Antenna

Dipole antenna is the simplest type of antenna from the theoretical point of view. However, the majority of the research on it focuses on adding supplementary structures for producing more resonant modes to achieve more functions. Here, we focus on the inherent modes of the dipole itself. The dipole antenna has alternating odd and even modes. In classical antenna theory, only odd modes are excited. The even modes are difficult to be excited due to their very high input impedances. In this paper, both odd and even modes of the dipole antenna are excited simultaneously by a single port with a novel feeding structure. Moreover, in order to tune the resonant frequencies of such multiple modes, a method by combining antithetical structures of indentations and outdentations is proposed and intuitively explained by eigencurrent distribution. By these new techniques, all the first six modes of the dipole antenna are excited, among which five modes are utilized for IoT applications. The antenna could cover ISM bands of 868 MHz and 2450 MHz, GNSS band of 1575 MHz, and 5G bands of 3500 MHz and 4900 MHz. This research could broaden the application of this classic antenna.