Segmental polynomial approximation based phase error correction for precise near field displacement measurements using Six-Port microwave interferometers

Six-Port microwave interferometers are a low-cost as well as low-power type of radar sensor with a high phase accuracy, which can be used for precise displacement measurements. Near field effects strongly influence the signal characteristics of a reflection of the electromagnetic wave near the antenna, especially if the target is low reflective. In this paper a calibration procedure based on phase error correction by segmental polynomial approximation is proposed that utilizes these effects. After validating the functionality of the calibration algorithm and its improvement by comparison to a comparable state-of-the-art procedure, two further near field measurements are presented. A cardboard as well as a plastic plate are used as low reflecting targets to show the applicability of the proposed calibration procedure for diverse measurement scenarios.