I. Introduction
Unmanned aerial systems (UAS) were developed for detecting, tracking and attacking the enemy and for surveillance. During war and times of disasters, the UASs are used to capture ground information and process that to identify threats and send the data to the ground control station (GCS). One of the most useful features of an UAS is delivering a live high definition video of the target region. This is a challenging task over long distance because it requires high transmission power. The type of antenna used greatly affects the transmission distance [21]. Omnidirectional antenna spreads the energy in all directions, so the loss of signal strength is very high and thus not suitable for long-range operation. Directional antennas emit the signal in one direction and thus it can reach longer distance with higher signal strength. The UAS keeps moving in the air, which makes it mandatory for the antenna to track the base station dynamically using tracking control mechanism. The current issue with the existing design is range, using omnidirectional transmitting antenna the energy gets divided into all directions which makes the signal get attenuated within a short range. The typical range of omnidirectional antenna is limited to a few miles, but the range of a directional antenna can be extended to 8 miles. By using a higher gain directional antenna, the range can be increased up to 15 miles [1].