Plastic wavguide for terahertz sensing in reflection

Guided Reflectometry Imaging Unit using Millimeter Wave FMCW Radars

In this paper published in july 2020 in IEEE Transactions on Terahertz Science and Technology, we present a reflectometry sensing system associated with a frequency modulated continuous wave radar. Then, a solid immersion lens is added to the system to improve the resolution.

Abstract of terahertz reflectometry setup

Frequency Modulated Continuous Wave (FMCW) radar systems in the millimeter and sub-millimeter range are technologically mature for many applicative fields such as automotive and aerospace industries for imaging and non-destructive-testing. This work reports on a new implementation of a guided FMCW radar reflectometry unit for sensing and imaging applications. Only a terahertz dielectric waveguide is used for signal transmission between the transceiver module and the sample, thus drastically simplifying the experimental setup. Compared to continuous wave guided systems, one of the main advantages granted by the use of FMCW radars in combination with waveguides is the differentiation capability between the reflected signals generated along with the waveguide parasitic signals or at its probing end as sensing information and therefore improving the expected signal-to-noise ratio. This innovative approach is demonstrated by using a dielectric hollow-core waveguide integrated with two different radar transceivers; the high-performance, III-V based 100 GHz SynView unit as a reference system and a compact, low-cost, PCB-Integrated, 122GHz transceiver developed by Silicon-Radar GmbH. Both 3Delectromagnetic simulations and raster scans are performed to investigate quantitatively the propagation behaviors including the coupling capabilities, dynamic range limitations, beam profile, and induced artefacts of the guided FMCW reflectometry system. The feasibility of a simplified guided terahertz FMCW reflectometry probing unit is proven. The integration of a solid immersion lens at the end of the waveguide is also demonstrated for imaging resolution improvement.

Selected figures

Setup using the III/V chain FMCW radar
FDTD simulation using CST microwave studio of the setup. We can see a self-focusing at the end the waveguide

We can improve the resolution using a solid immersion lens directly associated with the hollow core waveguide.

Access to IEEE Terahertz article

Access to the Paper with ResearchGate

M. Pan, A. Chopard, F. Fauquet, P. Mounaix and J.-P. Guillet “Guided Reflectometry Imaging Unit using Millimeter Wave FMCW Radars,” in IEEE Transactions on Terahertz Science and Technology, doi: 10.1109/TTHZ.2020.3008330.

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