Numerical Modeling of Ultrawideband Propagation Along a Wind Turbine Blade

Full-wave numerical analysis of an ultrawideband wireless link in frequency band 3-5 GHz along a 37.3 m long wind turbine blade is presented. The method used for the analysis is the well-established finite-difference time-domain (FDTD) method with staggered Yee mesh. Simulated results are compared to data obtained from measurement on a real blade, in two experiments involving antennas transmitting both from outside near the blade tip and from inside the blade. In the first experiment, when the wave is propagated along the entire blade and received near the blade root, the differences between the simulation and the measurement are found in pulse magnitudes within 3 dB and in delay within 1.5 ns. In the second experiment, the emitted waves are studied at only 10 m distance, but at higher elevations, and the error reaches 6 dB in magnitude and 1.9 ns in delay. Possible reasons for observed discrepancies between the simulations and the measurements are briefly discussed. Despite the long distances involved and challenges connected to the numerical dispersion and anisotropy, the FDTD method turns out to be a feasible choice for full-wave numerical modeling of problems of this type, albeit with slightly high sensitivity to the underlying model.