Abstract
This article presents an in-depth study of a new vector network analyzer (VNA)-based electromagnetic material measurement method relying on a commercially available material characterization kit (MCK). These MCKs provide effectively a guided free-space technique with less stringent requirement on alignment compared with conventional free-space techniques. Coupled with time gating, these MCKs employ a simple calibration, composed of reflect and thru standards only, prior to taking reflection and transmission S-parameter measurements. This MCK-based method complements other conventional measurement techniques, e.g., time-domain spectroscopy (TDS) and resonant cavity, allowing fast broadband dielectric material characterization over the millimeter- and submillimeter-wave frequency ranges. In this article, a WR-15 (50-75 GHz) MCK is utilized for the measurements of S-parameters for seven types of low-loss dielectric material. Their dielectric constant and loss tangent are extracted from S-parameters and are compared against literature values. A relatively good agreement is achieved. Moreover, an investigation into the uncertainties of the extracted dielectric constant and loss tangent is performed and reported.
Highlights
C HARACTERIZATIONS of low-loss dielectric material properties, such as dielectric constant ε and loss tangent tanδ, are of great importance for a variety of applications, including resonators, filters, lenses, substrates, and Manuscript received June 22, 2019; revised September 16, 2019; accepted November 5, 2019
The standard uncertainty for the loss tangent u was calculated using thickness, and the measured S-parameters of the sample. These estimates will be used to establish a preliminary assessment of the overall uncertainty of the material characterization kit (MCK) in the WR-15 waveguide band. This is not intended as a rigorous assessment of uncertainty, as this is beyond the scope of this article—rather, the intention is to provide an indication of the typical size of uncertainty that could be expected for these MCKs
This may not be the case for other materials and so this type of assessment should be considered for all materials measured using the MCK
Summary
C HARACTERIZATIONS of low-loss dielectric material properties, such as dielectric constant ε and loss tangent tanδ, are of great importance for a variety of applications, including resonators, filters, lenses, substrates, and Manuscript received June 22, 2019; revised September 16, 2019; accepted November 5, 2019. The free-space measurement method is widely utilized for low-loss dielectric characterization at millimeter-wave frequencies and beyond, and this method is nondestructive, noncontacting, and broadband [1], [2], [11], [14] This technique operates in a similar way to the above-mentioned transmission-line technique and uses the same methods to calculate dielectric constant and loss tangent. WANG et al.: CHARACTERIZATION OF DIELECTRIC MATERIALS AT WR-15 BAND (50–75 GHz) the need for large parabolic mirrors or lens, and this significantly reduces the overall size of the measurement system Note that these MCKs are not ideally suited to measure samples at varying temperatures—in these scenarios, the conventional free-space technique is likely to be more effective. In contrast to most conventional free-space measurement setups, these MCKs eliminate
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