Terahertz generation through photoconductive antenna (PCA) is quite popular mainly due to the advancement of nanotechnology and material research. An extensive investigation of the interdigitated photoconductive antenna (IPCA) in the terahertz (THz) frequency band has been carried out based on numerical modeling. An equivalent circuit model for IPCA based on its electrical perspective with corresponding expressions has been solved to understand the capacitive behavior of the gap between the interdigitated electrodes. This work explores the performance of IPCA with variation in structural parameters of their interdigitated electrode geometry in the active region. The interdigitated elemental periodicity, width and length of the IPCA are varied by keeping the interdigitated gap constant between the elements. The temporal behavior of generated electric field and its corresponding spectral response of the IPCAs with variation in the interdigitated electrode geometry has been compared. Moreover, the coupling behavior of the elements has been observed in the generated radiation. Finally, the results prove that the THz amplitude, frequency and efficiency can be enhanced by optimizing the structural parameters of the interdigitated electrode elements in the active region. This analysis is very useful while doing the practical experiments in spectroscopy, imaging and communication applications.