A review on six-port radar and its calibration techniques

The Six-port network is known for its high phase resolution and is therefore an interesting candidate for precise displacement sensors. This work gives an overview of Six-port networks and implementation technologies. Furthermore, several state-of-the-art calibration techniques are discussed, which are necessary to achieve accurate displacement measurements. The calibration techniques can be classified into four categories: calibration of baseband signals, I/Q domain calibration, phase linearization and detector linearization. Highest accuracy is obtained by a combination of two or more calibration steps.