Improved Free-Space Calibration Technique for Precise Measurement of THz Complex Permittivity

The accuracy of free-space complex permittivity measurements relies heavily on system calibration. However, existing calibration techniques often rely on high-precision system hardware or complex calibration procedures, which limit their universality and operational convenience in practical measurement scenarios. This issue is particularly pronounced in the terahertz (THz) band, severely compromising measurement reliability. This paper presents a free-space calibration technique tailored for the