Millimeter-Wave Characterization of Dielectric Materials Using Calibrated FMCW Transceivers

Abstract

This paper presents a measurement setup, an extraction algorithm, and the results from material characterization measurements in the millimeter-wave (mm-wave) regime using ultrawideband frequency-modulated continuouswave (FMCW) radar transceivers. The complex permittivity of dielectric and nonmagnetic materials is derived from radar echoes using a high-gain dielectric lens antenna setup and a measurement setup comprising elliptic mirrors. The radar transceivers perform fast and accurate measurements from 200 to 250 GHz within milliseconds. The FMCW transceivers are calibrated using a frequency-domain model that describes the systematic errors in the measurement setup. The characterization is done by a holistic model-based approach. Several well-known dielectric materials, such as polytetrafluorethylene, polyvinylchloride (PVC), or acrylic glass, are characterized among others to validate the setup's accuracy. The characterization is also done for different samples of polylactide, which is commonly used in additive manufacturing processes and 3-D printing, making it of high interest for the construction of mm-wave components.

Multilayer Thickness Measurements below the Rayleigh Limit Using FMCW Millimeter and Terahertz Waves

“…To counter this shortcoming, we included an optimized modification of the iterative TMM to our model, which describes the effects of complete wave propagation and enables an efficient implementation on graphics processing units. While we use simple brute force optimizations for our calculations, the implementation of more advanced optimization algorithms, such as in [14,15,16], can reduce the calculation time even further. We verified the suitability of our approach by validating the obtained measurement results with a set of well-defined calibration plates.…”

“…An alternative to VNA measurements with discrete frequency steps are millimeter-wave frequency-modulated continuous-wave (FMCW) radar measurements. Such an approach was presented recently for the characterization of single-layer dielectrics in [16]. Especially concerning industrial applications, millimeter-wave and terahertz FMCW transceivers can provide kilohertz measurement rates at a high level of integration [17].…”

“…In contrast to model-based frequency estimation algorithms such as in [19], our signal model enables the consideration of wave propagation aspects such as multiple reflections, which can be significant for the thickness measurements depending on the material parameters. To avoid possible variations in the measurement results, we used brute force optimization instead of more advanced optimization algorithms as in [14,15,16]. In industrial production environments, the material density may vary.…”

Millimeterwave Radar Systems for In-Line Thickness Monitoring in Pipe Extrusion Production Lines

“…Radar sensors can be used in various fields of nondestructive testing, including e.g., the thickness estimation of multilayer plates [11] or the identification of electromagnetic material properties [12]. The basic principle is the estimation of time-of-flight differences that occur from This work is licensed under a Creative Commons Attribution 4.0 License.…”

Indoor Material Properties Extraction from Scattering Parameters at Frequencies from 750 GHz to 1.1 THz

“…Meanwhile, the academia as well as industry are reviewing how this emerging terahertz eld might be implemented in a variety of real world applications by sharing their experimental database to the world, ranging from the materials' dielectric properties [10], material surface textures [11] and the molecular spectroscopic database [12]. To measure material spectroscopic responses, the state-of-theart THz systems based on time-domain and frequency-domain methods are classied as follows: (i) THz time-domain spectroscopy (THz TDS) systems [7]; (ii) THz quasi time-domain spectroscopy (THz QTDS) systems [13]; (iii) continuous wave THz (cw THz) systems [14]; and (iv) frequency modulated continuous wave (FMCW) radar transceiver systems [15]. However, each method is conned to specic frequencies, materials and applications in its own constraint.…”