A fast scanning short range radar imaging system for security or non-destructive testing applications is presented. The goal was to develop an 3D-imaging system with range independent lateral resolution down to 3 mm and a range resolution down to 6 mm. Therefore a setup with non focusing antennas and a broadband (75-100 GHz) SFCW (stepped frequency continuous wave) radar module were developed. A reconstruction of the device under test (DUT) with high lateral resolution is derived by applying numerical techniques based on the synthetic aperture radar (SAR) principle. To collect as many pixels as possible over a two dimensional aperture a rotating virtual antenna was developed. It is realized by a Gaussian beam transformation of the feed antenna beam waist onto a subreflector. By rotating the quasioptical transformator, an elliptical mirror, the transformed virtual antenna is rotated as well. This scanner concept is applied to planar and cylindrical geometries.