Novel Reflectometer for Millimeter-Wave 3-D Holographic Imaging

Small, portable, and wideband millimeter-wave imaging systems are used in many nondestructive testing and imaging applications, as these systems are capable of producing high-resolution images of the interior of composite structures. Typically, systems capable of producing holographic 3-D images incorporate expensive and bulky wideband heterodyne coherent reflectometers or commercial vector network analyzers. In many nondestructive testing applications, evaluation of electrical property distribution of an object is not of interest; instead, the geometrical distribution of the object is studied. In such cases, the use of coherent reflectometers that provides referenced information about the magnitude and phase of a reflected signal is not required. Consequently, simpler reflectometers, capable of producing 3-D holographical images of objects are of great value since they reveal significant information about the object. Moreover, 3-D holographical images enable production of image slices at different depths. This paper presents a novel wideband, small, and low-cost reflectometer capable of producing holographic 3-D millimeter-wave images. The design of the reflectometer, as well as several examples of produced images in diverse materials, is provided.