Improved evaluation of planar calibration standards using TDR preselection method

Calibration and correction methods for Vector Network Analyzer (VNA) are based on the fundamental assumption of constant error model, which is independent of connected calibration standards and/or devices under test (DUT). Unfortunately, this assumption is not satisfied well for planar calibration standards fabricated by etching technology on soft substrates. An evaluation of the error model is affected especially with a variation of the manufacturing process and also with a reproducibility of an assembly. In this paper, we propose error minimization using selection of the best combination of available calibration standards based on time-domain reflection (TDR) measurement. The proposed method was verified experimentally using short, open, load and thru (SOLT) standards fabricated on FR4 laminate substrate getting essential reduction of the measurement error in frequency range up to 15 GHz.