Abstract
Measuring the material parameters with a vector network analyzer (VNA) usually requires time-domain gating and complicated free-space calibrations. At terahertz frequencies, classic calibrations become more problematic and uncertainty calculation for time gating is not clearly defined. The here investigated method skips these steps and is based on normalization to a “Thru” connection and analyzing error terms and multiple-reflection phenomena (ripples). It is shown that at specific frequencies, the ripples are very small. Based on this, the “standard load” method is introduced, which simplifies the error correction for transmission and reflection measurements for the whole frequency range. Results are presented in 75–110- and 500–750-GHz bands with a quasi-TEM free-space setup. Various material slabs (thin, thick, lossy, and low-loss) have been tested to show the reliability and general usefulness of the method. This method that is initially based on a “Thru” connection only provides a simple and low-cost alternative to the conventional standards (Line, Match, Short, and so on) and calibration techniques.
Highlights
MEASUREMENT of material parameters at higher frequencies is still not a completely solved topic with important applications in telecommunications, autonomous vehicles, biomedical, space technology and more
The vector network analyzer (VNA) can operate up to 110 GHz and commercial frequency extension units are used for higher bands, currently up to 1.1 THz [1]
We showed the role of the MUT itself to reduce these effects a new technique is presented, called "standard load" method, to correct and reduce the ripples without filtering/averaging or time-gating
Summary
MEASUREMENT of material parameters (complex permittivity and permeability) at higher frequencies is still not a completely solved topic with important applications in telecommunications, autonomous vehicles, biomedical, space technology and more. The manufacturer suggests a classic calibration method and time-domain gating (as often used in many other commercial and research-oriented setups) of the measured scattering parameters (S-parameters) [9]. This calibration technique was used, e.g., for measurement of S-parameters and consequent retrieval of material parameters in [10]. In the CPEM-20 conference abstract [14] a simple technique was introduced briefly, which can be useful for the material characterization setups and for VNA calibration, in general This is of high interest because of the lack of reliable Match, offset-Short and Line standards at terahertz frequencies, where the very small wavelengths make challenging the precise-positioning and repeatability of measurements.
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