Enabling High Accuracy Distance Measurements With FMCW Radar Sensors

With the integrated radar technology being increasingly common in the automotive segment, it becomes even more cost-effective in other applications as well. Taking into account its price and robustness, radar sensors can be considered as a potential replacement for laser interferometry which is being widely used for accurate contactless sensing. In this paper we describe a phase evaluation algorithm for highly accurate distance measurements using linear frequency modulated continuous wave (FMCW) radar systems, considering hardware dependent effects i.e. frequency responses of the signal paths. In several investigations we show that this novel algorithm is significantly more robust against disturbing radar targets or micro vibrations than typical techniques. Distance measurements were carried out using an 80 GHz wideband FMCW radar sensor on a maximum measurement range of 5.2 m with a movable radar target. For free space measurements the unambiguous measurement accuracy was improved to ±4.5 μm, using phase evaluation techniques in a non-ideal environment over the entire measurement range, which was previously around ±120 μm with frequency evaluation techniques. Due to its robustness and accuracy, the proposed algorithm is well suited for harsh industrial environments such as real time positioning of machine tools.