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In recent years, unmanned aerial vehicles (UAVs), or drones have been widely adopted by many diverse industries and organizations, including military, public services, commercial, and even private individuals. The capability of drones to fly, carry an object and fly autonomously has made this technology life-changing in various ways. The military employs them for security and surveillance; rescue teams use them for 3D mapping of disasters; even the food industry is joining the wagon to make food delivery faster and easier. Just like any radio-controlled device, drones, quadcopters, or UAVs require antennas for their functioning. For successful operation of the drone mission, the communication between the drone and a remote control (RC) must be stable to avoid losing the drone. The instability, the drag issues, and interference are the main challenges that hamper the performance of the drones. 
 

HFWorks Modeling of Drone Antenna 

To contribute to this research effort, we used our electromagnetic virtual prototyping software, HFWorks, to design an antenna that is less susceptible to circuit interference, drag force and the effect of drone frame. The design of the antenna was obtained from the journal paper [1]. 

Y-Rounded Shape Antenna with a Convex Bending

The proposed antenna is low-profile and has a convex curvature which is convenient to minimize the drag problem during the operation of the drone.

 Fig. 1.  Top View 

 Fig. 2. Bottom View 

 

Fig. 3. Front View
 

The above antenna is simulated, and the following results are obtained:
 

Fig. 4. Return Loss of the Antenna

Fig. 5. 3D Radiation Pattern

Fig. 6. 2D Radiation Pattern( ?=0° )

From the above figures, we can observe that the antenna has a reflection coefficient of -12 dB at 5.8 GHz and a maximum radiation towards the ground. Such types of antennas are very suitable for drone applications such as 3D mapping and aerial shots.
 

Antenna on Drone

Antennas do not function independently of surrounding objects. The drone body has effect on the overall performance of the antenna due to reflection from metals and dielectric loading. Mounting the antenna on the drone is a real challenge.  Placing the antenna at the center of the drone makes it vulnerable to circuitry noise. Therefore, it is appropriate to place the antenna in the middle of the wings, where interference is less pronounced.  The drone frame was modeled using plastic; the motors are made of steel and copper. 

Fig. 7. Antennas on Drone

Fig. 8. Electric Field Animation (5.8 GHz)

Fig. 9. Return Loss

Fig. 10. Coupling Coefficients

Fig. 11. 3D Radiation Pattern

Fig. 12. 2D Radiation Pattern ( ?=0° )

The antennas have a maximum gain towards the ground. We can observe that there is a small distortion in the radiation due to the small difference in the permittivity between the substrate material and the plastic.  The motors, which are made of metals, have a small effect since they are far from the four antennas. The coupling coefficients are less than -30 dB at 5.8 GHz. This means that the antennas are well isolated and do not influence each other’s radiation; installing an antenna in each arm of the drone adds a spatial diversity to the system.
 

Conclusion 

FPV antennas play a crucial role in the quality of the transmitted video signal.  Low-profile and conformal antennas are indispensable for the successful operation of the drone mission. Placing the antenna on a drone is quite challenging for antenna engineers as there are many parameters to account for. Using a plastic material for the frame of the drone results in less distortion of the transmitted signal. Mounting the antenna in the middle of the wings helps reduce interference with the circuitry of the drone, while providing a reliable video signal. HFWorks has been instrumental in addressing antenna challenges and improving the drone performance.  
 

References 

[1]- L.L. Balderas1, A. Reyna, M.A. Panduro, C. del Rio, and A.R. Gutierrez, 2019, “Low-Profile Conformal UWB Antenna for UAV Applications”