Microwave Characterization of Low-Loss FDM 3-D Printed ABS With Dielectric-Filled Metal-Pipe Rectangular Waveguide Spectroscopy

Abstract

Over time, the accuracy and speed by which a material can be characterized should improve. Today, the Nicolson-Ross-Weir (NRW) methodology represents a well-established method for extracting complex dielectric properties at microwave frequencies, with the use of a modern vector network analyzer. However, as will be seen, this approach suffers from three fundamental limitations to accuracy. Challenging NRW methods requires a methodical and robust investigation. To this end, using a dielectric-filled metal-pipe rectangular waveguide, five independent approaches are employed to accurately characterize the sample at the Fabry-Pérot resonance frequency (non-frequency dispersive modeling). In addition, manual Graphical and automated Renormalization spectroscopic approaches are introduced for the first time in the waveguide. The results from these various modeling strategies are then compared and contrasted to NRW approaches. As a timely exemplar, 3-D printed acrylonitrile-butadiene-styrene (ABS) samples are characterized and the results are compared with existing data available in the open literature. It is found that the various Fabry-Pérot resonance model results all agree with one another and validate the two new spectroscopic approaches; in doing so, exposing three limitations of the NRW methods. It is also shown that extracted dielectric properties for ABS differ from previously reported results and reasons for this are discussed. From measurement noise resilience analysis, a methodology is presented for determining the upper bound signal-to-noise ratio for the vector network analyzer (not normally associated with such instrumentation). Finally, fused deposition modeling (FDM) 3-D printing can result in a non-homogeneous sample that excites open-box mode resonances. This phenomenon is investigated for the first time analytically and with various modeling strategies.

Benchmarking a Commercial (Sub-)THz Focal Plane Array Against a Custom-Built Millimeter-Wave Single-Pixel Camera

“…Moreover, the depths of these reflectance dips and reduction in detector sensitivity peaks both increasing with frequency. The PTFE cover (in isolation) exhibits almost perfect destructive interference troughs in reflectance, giving more than 99.5% transmittance at these Fabry-Pérot resonance frequencies [34], due to the low loss nature of PTFE at sub-THz frequencies. Moreover, with worst-case peak reflectance values of 12%, the corresponding worst-case transmittance is 88% (i.e., insertion loss of only -0.555 dB); with a 6.20% reflectance and 93.76% transmittance at 79 GHz.…”

Polymer-Based 3-D Printed Ku-Band Steerable Phased-Array Antenna Subsystem

“…With the Ku-band design adopted in this work, the dielectric insert taper profile and insertion mechanism were completely redesigned to improve RF performance, structural stability and control. The dielectric insert was designed to be FDM 3-D printed using acrylonitrile butadiene styrene (ABS), with Formfutura's Premium ABS (Frosty White), having X-band values of dielectric constant ε r = 2.31 and loss tangent tanδ = 20 × 10 −4 [8]. The guided wavelength,…”

“…15.8 at 15 GHz 17.1 at 17 GHz (8) where, the directivity for a broadside linear array of N uniformly-excited isotopically radiating elements is,…”

“…There is growing interest in utilizing the dielectric properties of polymer-based 3-D printed materials [8]. The dielectric properties of the polymers are easily tunable with composite filling materials and by varying infill densities.…”

Assessing the Impact of Data Filtering Techniques on Material Characterization at Millimeter-Wave Frequencies

“…[1]). There exist many different material characterization methods [2], and among them some popular methods are (presented roughly in order of increasing frequency): split-post dielectric resonators [2]- [3], coaxial probes [4], transmission lines [5], open-resonators [6]- [7], free-space methods [8]- [9], and Time Domain Spectroscopy (TDS) methods [10]. The open-resonators and free-space methods have been most widely used for measurements at millimeter-wave frequencies.…”