Standard Load Method: A New Calibration Technique for Material Characterization at Terahertz Frequencies

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.