Highly-efficient tunable dipole-driven Yagi–Uda antenna with end-fire radiation for terahertz application

This paper presents a highly efficient tunable dipole antenna with omnidirectional radiation. The main radiator of the hybrid dipole is designed using a perfect electric conductor, whereas tunability has been achieved using graphene strips in the antenna’s proximity. The dipole antenna resonates at 1.3785 THz and provides a bandwidth (BW) of 8.58% for the graphene’s chemical potential (${\mu }_c$) equal to 0.6 eV. The peak gain and total efficiency (${\eta }_{Total}$) are 1.46 dBi and 83.13%, respectively. The proposed dipole provides tunability from 1.32 to 1.411 THz by varying ${\mu }_c$ from 0.4 to 0.7 eV. Further, a compact dipole-driven tunable Yagi–Uda antenna has been designed with end-fire radiation. The proposed Yagi–Uda antenna has a size of only 90 $\mu$m $\times$ 60 $\mu$m, i.e., 0.61${\lambda }_g$ $\times 0.38{\lambda }_g$, where ${\lambda }_g$ is the guided wavelength calculated at 1.3631 THz and provides tunability from 1.328 to 1.5 THz. The peak gain, front-to-back ratio (FBR) and ${\eta }_{Total}$ at 1.3631 THz for the ${\mu }_c$ = 0.6 eV are found to be 4.93 dBi, 17.3 dB, and 63.36%, respectively. A practical parallel plate DC biasing configuration with a common ground plane has also been proposed to independently tune the ${\mu }_c$ of each element in the passive Yagi–Uda array. The proposed Yagi antenna provides reasonable gain and FBR to cater for high propagation loss in the terahertz regime.