Pieraccini, Miccinesi, and Rojhani Figure 7. 2D-ISAR image AirVision quadcopter. Figure 8. 3D-ISAR image of SYMA X5SC-1 quadcopter. gives a FWHM in range equal to 0.136 m, using a Kaiser window with β = 5. The obtained RCS image is shown in Figure 6. The shape of a quadcopter can be easily recognized. The four motors give a clear, high signal. The same measurements were performed with the AirVision quadcopter. The obtained RCS image is shown in Figure 7. Also in this case the shape of quadcopter can be easily recognized but, unlike SYNA quadcopter, the motors do not give the highest RCS signal. SEPTEMBER 2017 3D ISAR IMAGES The focusing formula in (3) can be applied to the 3D case by carrying out radar measurement at different height of the rotation plane. With this aim, the height of the platform was varied of 18 cm at step of 1.0 cm. The contour plot of the obtained 3D image of the smaller UAV is shown in Figure 8. The four blades are clearly recognizable, as well as the central body. IEEE A&E SYSTEMS MAGAZINE 31