THz waves are demonstrated as an efficient tool for non-destructive testing (NDT) but remain time-consuming and complex to use, particularly for curved parts. One solution is the multi-beam topology, using Luneburg lenses. However, this solution is generally unpractical above 40 GHz due to significant insertion losses caused by the materials used to produce the required graded-index profile. The idea is to use a near field focusing geodesic lens, or a variant, called the water drop lens, for performance enhancement, which is a novel concept first disclosed in the declaration of invention ESA-PAT-709 in 2016 and already tested at microwave frequencies. A system study, with the involvement of R&D Vision and Ariane Space, will be performed at the beginning of the activity to consolidate the system architecture and signal processing associated, to provide a system fully in line with the needs of the defined applications. In this project, we propose, first, to make a design and experimental validation of this near-field geodesic lens antenna in the sub-THz range. Then, a second step is to combine the lens with a terahertz frequency modulated continuous wave radar working in the 122 GHz ISM band, in order to build a demonstrator for sub-terahertz imaging. This development is of interest for NDT of launcher and aeronautic parts, including development and maintenance phases, aiming at a reduction of the control time and costs, while increasing safety. Even if single-pixel radars TRL is high, this geodesic antenna at terahertz frequencies and the integration with FMCW radar is at TRL 2-3, and the goal is to move to TRL 4, with a preliminary functional verification of the proposed system. To carry out this activity we propose an 15-month project with a cost of 175 k€ (90 k€ IMS& 85 k€ KTH). Compact multi-axis collision avoidance system could also be a spin-off application. Support of Ariane & RDVision are detailed in background.
