Characterization of quasi-optical focusing systems at W-band frequencies

In this paper we present an experimental method to investigate the imaging properties of quasi-optical focusing systems 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 Gaussian 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 scanning the signal is investigated and a calibration method is presented for adequate compensation.