A wideband linear tapered slot antenna is designed for widescan active phased array antenna. The results of computation and simulation show how the antenna has very high simultaneous bandwidth over X-band and widebeam scanning capabilities up to ±60°. The reflection coefficient is less than -10 dB over the operating frequency band. A Vivaldi notch antenna element is fed by stripline and may be coupled electromagnetically by tapered transitions. Stripline-fed Vivaldi antennas are comprised of: (1) a stripline-to-slotline transition; (2) a striplinestub and a slotline cavity; and (3) a tapered slot. The radiation characteristics, return loss, beamwidth and scan angle are achieved through the use of a commercially available electromagnetic simulation software HFSS by ANSYS. © Springer India 2015.