Guided Reflectometry Imaging Unit Using Millimeter Wave FMCW Radars

Frequency-modulated continuous wave (FMCW) radar systems in the millimeter and submillimeter range are technologically mature for many applicative fields such as automotive and aerospace industries for imaging and nondestructive 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 the wave guide as 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, printed circuit board (PCB)-integrated, 122 GHz transceiver developed by silicon-radar GmbH. Both three-dimensional electromagnetic 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.