Passive Millimeter Wave Imaging Camera ViKy as Technology Transfer of Planck-LFI

The passive Video camera for Imaging in Ka-band, named ViKy project, was born in 2004 as one of the possible spin-off based on the technology transfer of ESA PLANCK satellite thanks to an idea of Professor Nazzareno Mandolesi and Ing. Enrico Pagana. In 2004 the I ASF team - compound also by Ing. Adriano De Rosa, Dr. Carlo Burigana, Ing. Valerio Martorelli, Dr. Luca Stringhetti, Dr. Luca Valenziano, Dr. Fabrizio Villa and myself - ventured to raise the ViKy project. The aim of the ViKy system is to provide a real time optical image, obtained from the radiometric signal by imaging processing, for commercial applications. ViKy is a passive system because it does not need to illuminate the target (or an object in a scene) with an external radiation source as it happens for example in a radar system. The detected signal is given by the sum of the emitted and reflected component by the target object. The PPMMW imaging is a method of forming images through the passive detection of millimeter-wave radiation from a scene. In this way it is possible to form images during the day or night; in clear weather or in low-visibility conditions, such as haze, fog, clouds, smoke, or sandstorms; and even through clothing. This ability permits to see under conditions of low visibility otherwise visible or infrared (IR) sensors can do. In the commercial field such a system could be adopted by the airport companies to improve the capability of the security systems usually used to aid the aircrafts during the take-off or the landing phases. For security concerns, imaging of concealed weapons could be accomplished in a non intrusive manner with PMMW imaging. At system level the prototype can be separate in five units: the antenna ystem able to scan the scene quickly; the antenna electronics control that allows to carry out the scansion of the image; the radiometer that amplifies and detect the electromagnetic signal coming from the antenna; the Data Acquisition Electronics; the software for the image processing and the final interface. A key part of ViKy project is the design of a compact and low cost antenna working at 35 GHz and based on the reflectarray concept. Although this concept has been performed during the last years, only few 35 GHz reflectarrays exist. The reflectarray antenna consists of a flat reflecting surface and an illuminating feed horn placed in an off set or on set geometrical configuration depending on the requirements. On the reflecting surface, there are many isolated elements, named patches, which are designed to scatter the incident field and to form a planar wave front in the far-field. The second ViKy subsystem is the total power radiometer that was born from the millimeter waves technologies involved in the Low Frequency Instrument of PLANCK satellite. The radiometer amplifies and detects the signals coming from the antenna. The prototype that has been realized is based on a mechanical beam scanning necessary to reconstruct the image. In future will be possible to improve the ViKy system replacing the mechanical beam forming with an electronic beam forming using a particular kind of diode's technology. The data acquisition electronic and the software for the image reconstruction are the final subsystems of the imaging camera. All the ViKy components have been designed, assembled and finally tested by myself with the supervision of the IASF team. Mine PhD thesis summarizes the ViKy project starting from its principal and crucial aspects and finally presenting the results achieved. The measurements demonstrates the accordance with the required specifications. A pre-patent investigation highlighted the originality and newness of our project since to date no other passive system, coupled with a reflectarray antenna, has never been proposed. This demonstrates the full potential of the ViKy system in term of feasibility and commercial applications.