Second-order waveguide calibration of a one-port vector network analyzer

A method for second-order system correction of a calibrated vector network analyzer (VNA) is described. It is based on a single reflection measurement of an electrically long high precision waveguide section terminated by a flush short. The complex-valued residual error parameters, i.e. residual directivity, residual source match, and residual reflection tracking of a pre-calibrated VNA are determined by applying a sophisticated time- and frequency-domain data processing scheme which has been developed for coaxial measurements. Subsequently, using the complex-valued residual parameters, a second-order correction of the absolute error parameters results in a highly accurate VNA error correction. In this paper, the method is applied to waveguide measurements in the millimeter-wave range where the modeling of calibration standards, especially the inclusion of losses due to surface roughness, becomes difficult. Measurement results in the WR-22 (33-50 GHz) and in the WR-10 waveguide band (75-110 GHz) including a comparison with standard waveguide calibration methods demonstrate that a significant improvement of accuracy can be achieved by a managable additional operating expense.