Modeling the Effect of Aircraft Rotor Blades on Airborne Direction Finding (DF) Systems

Direction Finding (DF) systems on rotorcrafts vehicles and more specifically rotorcraft UAVs suffer from effects on rotorcraft blade modulations. Only coarse DF on rotorcraft has been achieved during the EH-60 QuickFix program. During this effort, Applied EM is proposing to develop very accurate modeling tools to predict performance of DF systems on rotorcrafts. DF arrays are normally designed without accounting for platform effects. When mounted on a UAV, the operation of the direction-finding array is greatly affected by interactions of the antenna elements with the UAV structure. For a fixed wing UAV, these effects are mitigated by calibrating the DF array with the UAV structure. But for a rotorcraft UAV they cannot be implemented due to the inherent dynamic conditions associated with the rotating blades. Our major contribution to the current technology will be the development of cohesive modeling tools to simulate the effect of rotating blades on DF system, and to recommend mitigation techniques that concurrently address low size, weight and power (SWaP) requirements.