GaAs based Photoconductive antenna (PCA) have widespread industrial uses as terahertz (THz) emitters for next generation wireless applications. It is well known, that a periodic-metallic structure at the edges of the antenna electrodes, similar to plasmonic PCAs, can extraordinarily increase the antenna performance. In this research, we have described the greater efficiency of Interdigitated-Slot Photoconductive Antenna (IPCA) as THz generators, than no-slot IPCA because of their higher screening electric field. Having a teeth length of 20 μm, width of 8 μm and a slot of 2 μm in the center, the reflection coefficient of -33 dB at 4.65 THz with a bandwidth of 0.515 THz has been achieved, whereas, with two slots around the center, the reflection coefficient is -17 dB at 2.835 THz with a bandwidth of 1.29 THz. The results show how frequency tunability and dual band radiation can be achieved by optimization of antenna parameters.