Wind turbine clutter mitigation using fully adaptive arrays

Doppler weather radar are susceptible to clutter contamination from both ground and airborne hard targets. Ground clutter can normally be mitigated through conventional filtering methods based on the assumption that the target is stationary. Wind turbines, which are becoming commonplace across the United States, are fixed in place but the blades rotate causing a significant Doppler shift in their signals. In fact, the blades rotate at such a rate to produce Doppler velocities on the order of 80 m s^-1. The wind turbines vane into the wind and therefore the radial component of their motion is not known a priori. This so-called wind turbine clutter (WTC) is problematic because of its non-zero Doppler velocity and is known to cause significant artifacts in weather radar data. Here, the spectral signature of actual WTC from an S-band NEXRAD radar in the United States will be studied. Several examples will be provided proving the challenge in dealing with this interference. As a possible solution, adaptive phased array radars will be proposed as a concept for interference rejection. Sophisticated numerical simulations will be provided, which show the limitations and benefits of adaptive arrays for mitigating WTC.