Full wave numerical analysis of wideband and high directive log spiral THz photoconductive antenna

Abstract

This study presents, for the first time, a novel design of ultra-wideband (UWB), circularly polarized and highly directive log-spiral THz photoconductive antenna. The proposed antenna is simulated in High Frequency Structure Simulator using gold as the antenna electrode material which is backed by a quartz substrate (εr = 3.78, tan δ = 0.0001) and hemispherical silicon-based lens with a diameter of 140 μm. A comprehensive detailed parametric study of the antenna design parameters is performed in the frequency range of 1 to 6 THz for the optimal design of the developed antenna structure. The optimal antenna structure with integrated lens has UWB characteristics with −10 dB impedance bandwidth of 5 THz and 3 dB axial ratio bandwidth of around 4 THz. The observed directivity and half-power beam width of the presented design varies in the range 5 to 12 dBi and 34° to 62°, respectively, for the frequency range of 1 to 4 THz. The wideband, high directivity as well as high-efficiency (>50%) characteristics of the proposed design make it a favorable choice for the THz sensing and imaging applications. Keywords: High directivity, Log spiral antenna, Photoconductive THz antenna, Wideband