Guided Reflectometry Imaging Unit Using Millimeter Wave FMCW Radars

Abstract

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 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 hollowcore 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, 122 GHz transceiver developed by Silicon-Radar GmbH. Both 3D 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.

Terahertz non-destructive testing of power generator bars with a dielectric waveguide antenna

“…In general, the aim is to provide strong guidance of the terahertz waves and at the same time keep radiative losses at an acceptable level. Various approaches exist [13][14][15], where the specific implementation of dielectric waveguides may, for example, be realized in the sense of hollow-core and porous-core fibers [16,17] or as solid dielectric materials, sometimes referred to as ribbons or dielectric rod waveguides or microwires [17][18][19][20][21][22][23][24] exploiting total internal reflection. Even the combination of dielectric rods with embedded substrate lenses has recently been investigated for integration with antenna emitters [25].…”

“…Dielectric waveguide antennas can be realized in various forms and offer sub-wavelength imaging resolution in combination with relatively simple manufacturing methods and versatile design freedom, depending on the dielectric material. The antennas can be easily integrated into typical waveguide horns of electronic terahertz systems to ensure efficient power coupling to the dielectric [13,16,[19][20][21].…”

“…We will first introduce the FMCW concept and then discuss the implementation of our dielectric waveguide antenna. It should be mentioned at this point that recently, the use of a hollow dielectric waveguide antenna in combination with a comparable terahertz transceiver unit was presented in the literature [16]. Although a slightly different approach was employed there, the reader may find some of the theoretical considerations and simulations on forward power coupling and beam profiles useful for further insight.…”

Research on wingtip distance measurement of high-speed coaxial helicopter based on 77 GHz FMCW millimeter-wave radar

“…The current mainstream products are 24 GHz and 77 GHz millimeter wave radar, of which the bandwidth of 77 GHz can reach 4 GHz, the theoretical range resolution can reach 37.5 mm, and the range accuracy is at the centimeter level [2]. At present, the research focus of FMCW millimeter-wave radar is mainly on environmental perception in autonomous driving, including radar imaging [7][8][9][10], pedestrian detection [11], fusion positioning [12], pattern recognition [13,14] and other directions, close to the direction of artificial intelligence. In these application scenarios, centimeter-level accuracy is sufficient.…”

Fast FMCW Terahertz Imaging for In-Process Defect Detection in Press Sleeves for the Paper Industry and Image Evaluation with a Machine Learning Approach

“…With suitable materials for quasi-optical components, e.g., the polymers PE and PTFE, the radiation can be easily guided and focused according to the specific context of application with quasi-optical lenses [ 23 ], typically produced of low-cost materials such as the polymers PE and PTFE, and diffractive elements [ 24 ], or with simple metallic mirrors. In addition, guiding and focusing of the radiation with easy-to-fabricate dielectric waveguide antennas has been demonstrated [ 25 , 26 ]. Combining all the above properties and advantages over other NDT techniques, and the increasing availability of sources, detectors and receivers, terahertz technology has today reached a level of maturity to be implemented in industrial production environments or processes of quality control and to offer a valuable benefit in the optimization of these processes.…”