FDTD modeling of helicopter antenna pattern rotor modulation

Rotor modulation is the periodic disruption of electromagnetic communication signals caused by the rotation of lift or thrust generating propellers on aircraft. Rotor modulation is predominantly associated with helicopters because their very large main rotor can cause intense modulation effects, and their comparatively small fuselages provide few antenna mounting locations at which rotor modulation can be avoided. Rotor modulation modeling, because of its complexity, has not received very much attention. We use the finite-difference time-domain (FDTD) method to model the radiation patterns of antennas mounted on helicopters, including the modulating effects due to the motion of the rotor blades.