Reduction of radar interference-stealth wind blade structure with carbon nanocomposite sheets

Wind turbines appear to be an ongoing threat to radar systems because of their large radar cross-sections (RCS). In particular, the Doppler shift of the radar signal caused by blade rotation can confuse even modern Doppler radar systems. To reduce the radar interference problem, this study presents a stealth wind blade structure with a minimal weight increase compared with the conventional wind blade structure, while maintaining the same manufacturing process. The Salisbury screen-type absorbing structure with a carbon nanocomposite sheet was adapted for the wind blade. The radar-absorbing structure was integrated with the wind blade structure by sharing the spacer and ground of the absorbing structure with the wind blade structure. A ply of carbon fabric was used as the ground, for which the reflection was verified to be greater than-0.078dB over the whole range of X-band frequencies. The radar-absorbing structure was designed to have a reflection loss greater than-40dB at 10GHz. The stealth wind blade structure was manufactured via the resin transfer process used for conventional wind blades. The RCS reduction performance of the stealth wind blade was measured in the compact range at 10GHz, and an RCS reduction of nearly 20dB was achieved in the angle range of the most severe RCS.Copyright (c) 2013 John Wiley & Sons, Ltd.