In this paper, a study of a stripline dipole antenna on a substrate lens used as a photoconductive detector in a terahertz system is presented. The traveling-wave behavior of the stripline dipole and the influence of the substrate lens are investigated over a broad frequency range up to 5.0 THz. The numerical results show that the lens shape represented by the ratio of the extension length to the lens radius plays an important role in maximizing the antenna gain and radiation spectral bandwidth. The gain response exhibited an increased level of sensitivity to the lens shape as the lens size increased, and this is particularly important in optimizing large substrate lenses. Improvements in the gain level over the entire frequency range of interest were observed as the lens diameter increased. This study provides helpful guidelines in choosing and optimizing a substrate lens designed for a terahertz photoconductive antenna, which is particularly useful for specific applications requiring a miniaturized photoconductive antenna design. (C) 2014 Elsevier B.V. All rights reserved.