Abstract
In this paper we present an experimental method to investigate the imaging properties of quasi-optical focusing sys-tems at frequencies between 75 GHz and 110 GHz. Therefore, a millimeter wave beam which is focused by parabolic mirrors is scanned in 3D by a movable Rx horn antenna. The beam can then be visualized and analyzed using a Gaus-sian beam model. In order to characterize the performance of the quasi-optical system, the minimal spot diameter of the millimeter wave beam at the target is determined. Furthermore, the influence of the Rx horn antenna used for scan-ning the signal is investigated and a calibration method is presented for adequate compensation.