To meet the high gain requirement, a 2×2 a microstrip patch antenna array is designed and used as a feed source to illuminate a symmetric parabolic reflector antenna at 300 GHz. The effect of the substrate and conductor material properties on the performance of the microstrip array antenna is discussed. Resulting reflector antenna performance is discussed using this feed. Another application of this array is to excite dielectric lens antennas for high gain. These high gain antennas can find application in future THz communications.