Design of Low-Cost On-board Auto-tracking Antenna for Small UAS

Unmanned Aerial Systems (UAS) are being used commonly for surveillance providing valuable video data. High quality video transmission is a must feature for this purpose. The radio signal from the UAS is transmitted generally over Omni-directional antennas, but the attenuation rate is very high and the transmission distance is severely limited. For achieving longer distance, directional antennas can be used where they should be pointing towards each other for maximum signal strength. A moving aircraft requires an antenna which dynamically points towards the ground control station (GCS). The tracking antennas currently being used are usually placed on the receiver side on the GCS and track the aircraft based on the signal strength. This method is inefficient when the aircraft movement is fast and makes it difficult to retrieve the aircraft related data once some snap occurs in tracking process. This research is aimed at developing a low cost precise tracking antenna which can be mounted onto any aerial system which needs long-distance video transmission. This system consists of inertial measurement unit, global positioning system, and servo motors to direct the antenna. It tracks the GCS using both the gyro sensor and GPS data such that even if one system fails, another one is available as a backup. This system implements tilt compensation in both x and y axis using the accelerometer in the IMU.

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].