A least-squares approach to the calibration of multiport reflectometers

A novel two-step calibration of multiport reflectometers, employing the least-squares fitting approach, has been presented. The proposed procedure can be applied to any linear multiport, having an arbitrary number of ports. In the first calibration step a numerical procedure, based on the Levenberg-Marquardt algorithm for a least-squares curve-fitting problem is used. In the second step, a reflectometer is modeled as a connection of an ideal reflectometer and an error box network. The proposed modified analytical procedure, which provides the error box parameters, allows for further decrease of a measurement error. The performance of the presented calibration procedure has been experimentally verified, by measurements of two calibration standards. The measurements performed in a wide frequency range 2-3 GHz have shown that the proposed algorithm features high accuracy and robustness to the applied power detectors' uncertainty.