Target evaluation for high accuracy 80 GHz FMCW radar distance measurements

Abstract

Distance sensing tasks in micromachine tools need to be performed with micrometer accuracy. For such tasks, FMCW radars with a combination of frequency and phase evaluations are a good choice. However, the accuracy cannot be freely increased as there are constraints on the target size and placement imposed by the limited space inside micromachines. This paper investigates the influence of target geometry and position on the accuracy of its range estimation using a W-band FMCW radar. A relation between target geometry and accuracy is established through Cramér Rao Lower Bound (CRLB). Based on the measurements of different targets, an optimal shape and size is proposed which provides an average accuracy in the single digit micrometer range. In addition, antenna field regions are analyzed for suitable target placements.