Characteristic Mode Analysis based Flower Shape High Gain THz Antenna for Imaging and Defense Applications

The intriguing features of terahertz (THz) waves captivated the curiosity of many researchers toward THz technologies. This paper introduces a high-gain composite structure consisting of a circle and rectangle with a rectangular monopole antenna for terahertz (THz) imaging and defense applications. The projected THz antenna is designed on a $20 \mu \mathrm{m}$ thick polyimide substrate with a relative permittivity of 3.5. A ground plane is lowered to have wider impedance bandwidth for the conventional rectangular patch. The lowered ground plane alters the transmission line characteristics, and therefore quality factor reduces, which impacts improved bandwidth. Furthermore, to achieve the appropriate operational frequency, the antenna’s radiator is adjusted by inserting a sequence of circles and a rectangle. The proposed flower shape antenna operates in the frequency range of 0.096-0.701THz, having an overall dimension of $600 \times 600 \mu \mathrm{m}^{2}$. The variation of gain in the operational frequency varies from 8.7 dB to 10.8 dB; at the resonant frequency of 0.2 THz, the gain is 10.8 dB. To gain a better physical understanding, the projected antenna is exposed to a characteristic mode analysis. The proposed antenna is appropriate for imaging systems (0.6 THz) and military applications (0.7 THz).