Antenna Gain Impact on UWB Wind Turbine Blade Deflection Sensing

Antenna gain impact on ultra-wideband wind turbine blade deflection sensing is studied in this paper. Simulations are applied with a 4.5-m blade tip. The antennas with high gain (HG) and low gain (LG) in free space are simulated inside a blade. It is interesting to find that tip antennas with HG and LG in free space have similar realized gain when allocated inside blades, so that the emission power for the HG and LG antennas in blades can be the same. The antenna gain impacts on time-domain pulse waveforms and power distributions around a blade are carefully investigated (with the tip antenna inside a blade). Higher antenna gain enlarges both direct pulse and multipath but in different levels. To verify the simulations, time-domain measurements are performed with a full 37-m blade. Pulse waveforms and power delay profiles are measured. From all the studies, it follows that, with the similar effective (or equivalent) isotropic radiated power, an HG tip antenna inside a blade gives stronger direct pulse amplitudes and better pulse waveforms for accurate and reliable distance estimations than the LG. Moreover, the direct pulse with the HG antenna is also closer to the blade surface, which is important for the deflection sensing of a blade over 37 m.