Design of Flush-mountable Wideband Antenna for UAV Applications

Abstract

A UAV (unmanned aerial vehicle) has received increasing attention in various military and commercial markets. To establish successful communication links between a UAV and a ground control station, the radiation characteristics of the antennas for UAV applications are very important. These applications require the antennas that provide omnidirectional radiation in a wide operating frequency band, like a mono-cone antenna, to maintain robust communication links. However, a conventional mono-cone antenna has protruding in shape, which makes the antenna difficult to be embedded in UAV. A cavity-backed antenna is conformal in shape, which has an advantage in drag problems and potential breakage. However, a typical cavity-backed antenna has narrow bandwidth characteristics. To overcome the limitations, a flush mountable antenna with an exponentially tapered cavity is proposed. The antenna can improve the performance of a cavity-backed antenna. By suppressing resonances inside the cavity, the flush mountable antenna with an exponentially tapered cavity has quasi-omnidirectional radiation patterns in the wide operating frequency band.

Finally, a dual mono-cone antenna with the helical feeding structure is proposed to attain additional high operating frequency bands. The antenna consists of a mono-cone antenna operating in a low frequency band, a mono-cone antenna operating in a high frequency band, a circular cavity with an exponentially tapered profile, a helical feeding probe, and a short-circuited wire. By embedding the small (additional) mono-cone inside the top surface of the large mono-cone, the additional high operation frequency band is obtained while being the same size as the antenna proposed in chapter 3. The proposed antenna also has a lightweight feature by using a conductively coated 3D printed antenna structure. The proposed antenna has a wide -10 dB reflection coefficient bandwidth ranging from 1.43 GHz to 39.0 GHz and has quasi-omnidirectional radiation characteristics in the operating band. Therefore, the proposed antenna is suitable for UAV applications.