We proposed the 4-leaf clover-shaped antenna structure which can improve the output power of THz photomixer through the high input impedance characteristics. By optimizing the structure antenna total efficiency was expected 2.7-fold higher than that of the full-wave dipole on the pbg biasline condition. In the optimization of extended hemispherical lens substrate, the proposed structure showed the maximum directivity at the thicker substrate condition than dipole on the same hemispherical lens.
