Free-Space Unknown Thru Measurement Using Planar Offset Short for Material Characterization

Material characterization requires the proper calibration of a material measurement system. This paper describes a free-space unknown thru measurement method using three independent planar metal offset shorts for calibrating a free-space material measurement system. This method is validated by comparing the measurement results with those of the TRL (thru-reflect-line) measurement method for two glass plates of 2.780 mm and 4.775 mm thickness in W-band (75–110 GHz). This can be an affordable and effective alternative to conventional free-space material measurement methods because the precision fabrication of a planar offset short is more feasible and inexpensive than building a precise positioning system in a free-space material measurement system. One can use this measurement method up to a high-frequency range that the fabrication accuracy of a planar offset short is acceptable.