State Observation Using the Phase and the Beat Frequency of a FMCW Radar for Precise Local Positioning and Line-of-Sight Detection

The accuracy of an FMCW radar working in a multipath environment is mainly limited by the radar signal bandwidth. Furthermore, the separation and identification of line-of-sight (LOS) and non-line-of-sight (NLOS) signals are important and challenging problems in many radar and local positioning applications. In this article, a method is proposed to overcome these restrictions. A state observer is used for an improved fusion of the FMCW radar beat signal frequency and phase. It is shown that the concepts allow for an accuracy improvement of more than one order of magnitude. In addition, the new approach is able to distinguish between NLOS and LOS measurements. The robustness of the system is improved by the implementation of motion type detection algorithms. Practical experiments illustrate that the new technique is superior to standard FMCW radar location methods.