Spatial filtering of wind turbine clutter using adaptive phased array radars
R. D. Palmer, Atmospheric Radar Research Center, School of Meteorology, University of Oklahoma, Norman, OK; and K. D. Le, B. M. Isom, and S. M. Torres
Doppler weather radars are susceptible to clutter contamination from both ground and airborne hard targets. Ground clutter can normally be mitigated through conventional temporal filtering methods based on the assumption that the targets are stationary. Wind turbines, which are becoming more and more commonplace, have a fixed location 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/sec, which is significantly larger than typical Nyquist velocities. 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. Phased array radars use antennas, which are made up of thousands of individual elements, allowing rapid beam steering. An important example used for weather observations is the S-band Phased Array Radar (PAR) in Norman, Oklahoma, which is operated by NOAA's National Severe Storms Lab (NSSL). In the case of the PAR and most phased array radars, the phase and amplitude (complex weights) fed to each of the antenna elements are controlled in a systematic and predetermined manner. In contrast, future multi-mission phased array radars will likely have the capability of adapting the weights applied to each element, or groups of elements called subarrays. In either case, unprecedented control over the exact shape of the beam pattern will be possible. Using these adaptive phased array radars, it will be possible to implement spatial filtering, or null steering, in order to filter interference with non-zero Doppler characteristics, such as WTC. In this presentation, sophisticated numerical radar simulations of adaptive phased array weather radar will be used to assess this possibility. Results from statistical analyses will be presented along with a study of the advantages and challenges of the use of adaptive phased arrays for future weather radars.
Session 8B, Radar Applications - Session I
Wednesday, 14 January 2009, 8:30 AM-10:00 AM, Room 122BC
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