Transmission Line Impedance Characterization Using an Uncalibrated Vector Network Analyzer

For determining the line characteristic impedance Z
₁
of uniform transmission lines, it is typically necessary to use a calibrated vector network analyzer (VNA), whose calibration reference impedance Z
₂
is known. Using the eight-error term model for modeling a VNA and based on the fact that the values of the error terms are unique and independent of the calibration structures used to determine them, a new method for determining the line characteristic impedance of uniform transmission lines is presented. The main feature of the new method is that it only uses S-parameter measurements of a thru-line and a thru-load combination measured with an uncalibrated VNA.