Abstract
Recently a progress in computational imaging has been noticed with the potential to improve the capabilities of millimeter-wave imaging systems. In this paper, an interferometric synthetic aperture systems is considered to be the conventional approach to image reconstruction that, in order to overcome its cost limitations and system complexity, both hardware and digital post-processing solutions are offered. A passive multiplexing cavity is added to encode received signals into the physical layer helping to reduce the number of measurement ports and thus the active RF chains without affecting the initial number of receiving antennas. This proposed technique leads to inverse problem solving process. A novel numerical method is then developed, based on a matrix formalism yielding a mathematical description of the computational approach. A numerical study is therefore performed to approve the feasibility of this technique for a better image reconstruction followed by an experimental study carried out at 92 GHz as a proof of concept.
Highlights
Under the impetus of many recent technological advances, passive microwave and millimeter wave imaging has found numerous applications in several disciplines
Many millimeter wave radiometers and sensors including SPO-NX QinetiQ [7], TAC-camera (ThruVision), the Millivision imaging system X350 and MM-IMAGER 90 (Mc2 technologies) [8] reveal that researchers and companies have been interested to millimeter wave imaging technology for detecting suspicious object hidden beneath clothing that can be used in the entrances to airports, train stations, malls, sports arenas and other areas to ensure more secure environments
To conclude this section and in summary of the proposed developments, this study has introduced a matrix formalism to clearly show the relationship between the radiometric temperature of a target and the correlation of the signals measured on the ports of a computational imaging system
Summary
Under the impetus of many recent technological advances, passive microwave and millimeter wave imaging has found numerous applications in several disciplines. Computational techniques were implemented to reduce the number of active chains required for interferometric imaging systems by adding various types of components for encoding signals into the physical layer quoting code-modulated arrays [16], frequency dispersive reflectarray antennas [17], dynamic metasurfaces [18] and electrically large metallic multiplexing cavities [19]–[23] The latter is based on the use of passive coding devices initially developed in the microwave domain and adapted to the millimeter wave range [24]–[26]. The matrix-based formalism is adapted for short range systems where a computational approach is considered involving a numerical study of achievable performances, as well as an experimental demonstration at W-band of noise sources localization
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