Complex S-parameter measurement and its uncertainty evaluation on a vector network analyzer

Abstract

The present paper deals with an uncertainty evaluation in complex scattering (S)-parameter measurements and the correlation coefficients between the real and imaginary components of S-parameters in the frequency range 2–18 GHz. The measurements were performed for one-port and two-port components using a vector network analyzer (VNA) and the uncertainty estimation for complex transmission and reflection coefficients were done separately. The various contributors to the measurement uncertainty in real and imaginary component of S-parameter have been evaluated as per the European cooperation for Accreditation (EA) Guidelines on VNAs. Uncertainty budgets have been provided for one/two-port components separately with various sources of uncertainties involved and their distribution. This paper reports the combined standard uncertainty within ±0.005 and ±0.015 in complex transmission and reflection coefficients, respectively, upto 18 GHz. The correlation coefficients (+1.0 to −1.0) between the real and imaginary components of S-parameters are calculated for a coaxial mismatch of voltage standing wave ratio (VSWR) ≈3.0 and a coaxial attenuator (3 dB) in Type-N connectors.