Electromagnetic backscattering from aircraft propeller blades

This paper gives a theoretical solution to the problem of determining the electromagnetic backscattering and Doppler spectrum of an aircraft propeller as presented to a radar operating in the 8-12 GHz band. At this band for all practical aircraft propeller the electromagnetic backscattering regime is in the optical region. The solution proceeds by modeling the aircraft propeller as a set of multiple skew-plated metal fan blades in the presence of a linearly polarized EM wave. Based on the quasi-stationary method combined with physical optics and physical theory of diffraction equivalent currents techniques are used to analyse the backscattering from aircraft propeller blades. Experimental results indicated that, in the far zone, the field can be considered as harmonic and expressions for the spectral components of the field are obtained. The observed waveforms are found to be in good agreement with theoretical results.