The radar backscatter from turbines simulated by wire structures with angular periodicity

A rotating set of radial wires with angular periodicity about the axis of rotation scatters an electromagnetic wave to produce a spectrum of frequency components characteristic of the structure and its rate of rotation. The spectrum and its properties are predicted through electromagnetic scattering theory. Many of the predictions have been confirmed by direct computation using the NEC program[l]. Conclusions drawn from the study of wires are extended to structures in engine turbines. Predictions are possible of many of the new effects to be expected such as those of blades in place of wires, multiple stages, stator blades, stages of different speeds etc. These results have relevance for the identiflcation of aircraft by radar.