Development of the Line Scatterer Model for Bistatic Wind Turbine Clutter

The scattering of electromagnetic signals from wind turbines is a potential cause of clutter especially for passive radars which may use for example commercial Digital Video Broadcasting – Terrestrial (DVB-T) or frequency modulation (FM) broadcasting transmissions as transmitters of opportunity. These transmitters typically have a nearly constant gain in azimuth and thus they will illuminate the wind turbines at all times if they are visible to the transmitter mast. Understanding the wind turbine clutter is a first step in mitigating its negative effects. A previously published analytic line scatterer model for wind turbines is developed further in this work. Elevation angles are taken into account and thus the transmitter, wind turbine and receiver locations are no longer limited to the plane of same height. Furthermore, the amplitude of the scattered signal in the line scatterer model is investigated in detail and compared to radar cross-section (RCS) simulations from a 3D model of a wind turbine rotor. Based on this comparison, frequency dependent models for the amplitude are developed. The model development shows that wind turbine RCS can be highly dependent on frequency and view angle, but simplified models can also give quite good predictions. One possible application of the model is demonstrated by simulating a passive radar signal processing scenario where the effect of the blade flashes can be seen in the cross-ambiguity function (CAF) computation.