High directivity, lens-less THz photoconductive switch dipole antennas

We present several linearly polarized terahertz (THz) photoconductive switch antennas that have been designed for a compressive sensing-based THz imaging system which is currently being brought online. A bow-tie based antenna, including a finite ground plane (on the side of the substrate opposite the bow-tie) and its DC bias lines, is the reference design. By incorporating a metamaterial-inspired artificial magnetic conductor (AMC) structure, the directivity is increased by almost 3 dB at 1.05 THz. The simulation results show that the radiation efficiency of this bow-tie AMC-augmented antenna is above 85% at 1.05 THz. A single capacitively-loaded dipole antenna is then introduced; it has a 12.8 dB directivity, a 11.6 dB realized gain, and a 82% radiation efficiency. By connecting two single capacitively-loaded dipole antennas to form a linear array, higher directivity (14.8 dB), lower sidelobe level (-18 dB) and larger front-to-back-ratio (14 dB) values are achieved. Additional designs will be given in the presentation, including the incorporation of a meta-film structure to decrease the sidelobe levels and increase the front-to-back ratio.