Wideband Ferrite-Loaded Bow-Tie Antenna of Extremely Low-Profile

A large ground plane can severely degrade an antenna’s performance if its polarization is parallel to the ground and its profile is only a very small fraction of the operating wavelength. In this article, a wideband and very low-profile bow-tie dipole antenna is proposed to operate in the VHF/UHF band, which can be placed above a large ground plane. A step-by-step design with three main strategies: adding parasitic shorted walls, inserting parasitic triangle patches, and employing ferrite material, is introduced to make the antenna radiate in a wide band and maintain a very low profile. Another two methods using folded strips and modified interfingered structure are adopted to achieve the challenging goal of its realized gain greater than 2.0 dBi over a bandwidth of 218–650 MHz. The antenna’s profile is only <inline-formula> <tex-math notation="LaTeX">$0.036~\lambda _{0}$ </tex-math></inline-formula> and its area is only <inline-formula> <tex-math notation="LaTeX">$0.22\times 0.44\,\,\lambda _{0}$ </tex-math></inline-formula>, where <inline-formula> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> is the free-space wavelength at the lowest frequency of 218 MHz. Experimental verification is carried out, and the measured results are in good agreement with the simulated ones.