Broadband circular interferometric millimetre-wave ISAR for threat detection

To detect threats on a person's body surface the application of millimetre-waves is possible. In order to get a view of the person from all sides either the person has to be rotated standing on a turntable (Inverse Synthetic Aperture Radar, ISAR) or a sensor is moved on a circular path around the person (Synthetic Aperture Radar, SAR). The goal of the reconstruction is to obtain information about the shape of the threats and their positions in all three dimensions. At first the reconstruction is done along range and azimuth, which span the principal surface given by the sensor configuration. This paper reports on two methods to obtain the third spatial dimension. Due to the circular shape and its 3D focussing ability of the aperture this information can be obtained by the evaluation of the image focus. Secondly, if two coherent receiving channels are used, a possibility to achieve 3D spatial resolution is the processing of the interferometric phase. A comparison between these two will be presented.