The Near-Field Radar Cross Section Estimation of Wind Turbine: Mitigating Radar Clutter Caused by Wind Turbines by Proper Siting

As the wind energy develops, many wind farms are built across the country, where an increasing number of utility scale wind turbines are being installed. These extremely large structures are high above the ground and can potentially interfere nearby radars. If the wind turbine falls into ranges from several kilometers to several tens of kilometers from the radar, they can cause clutter effect, known as the Wind Turbine Clutter (WTC) in the radar community. The increasingly large wind turbines have extremely large Radar Cross Section (RCS), yielding high Clutter to Signal Ratio (CSR). Also, the blade rotation may cause complicated Doppler contamination. Therefore, radar performance can be potentially compromised in the presence of WTC. As a result, many wind farm projects have been postponed, stalling the development of wind energy. RCS is generally used for preliminary evaluation of the impact of a wind turbine on nearby radars. Estimation of wind turbine RCS is extremely difficult due to its large size and multiple degrees of freedom. Because of the large dimension, the far field criterion conveniently assumed by many RCS calculation techniques is violated in the wind turbine case. Therefore, we introduce a target decomposition method to break the large wind turbine into small parts that meet the far field criterion and then coherently integrate the backscattered electromagnetic field to approximate the near field RCS of the wind turbine. As expected, the calculated near field RCS varies as the range between radar and wind turbine changes. Simulations indicate that the same wind turbine will have significantly smaller RCS around certain ranges than the others. This implies that the wind turbine radar interference can be mitigated by proper selection of the range, which can be taken into consideration of siting.