Design of highly directive lens-less photoconductive dipole antenna array with frequency selective surface for terahertz imaging applications

In this paper, a highly directive photoconductive dipole array antenna is presented for imaging system operating at terahertz (THz) frequencies. The array antenna is formed on a single photoconductive substrate to make it compact and suitable for THz imaging applications. The presented photoconductive dipole array antenna improves the gain as well as directivity and therefore, is useful to enhance the imaging capabilities to address the considerations such as limited depth-of-field (DoF) that is the distance over which an object is considered in focus and size-weight-and-power (SWaP) of THz source for imaging applications. These are important considerations for applications like stand-off imaging and surveillance of moving targets where the high angular resolution as well as extended DoF is the key for successful detection of hidden explosives and illicit drugs. In addition to this, a technique of using frequency selective surface with photoconductive array antenna is also presented to further enhance the directivity of the radiating structure to yield high image resolution. Moreover, by using this technique, the radiation energy has been confined to the desired frequency band rather than spreading over a wide spectrum range.