Analyzing the Precision of Frequency Modulated Continuous Wave Distance and Thickness Measurements

Using millimeter and terahertz waves, novel solutions to nondestructive testing can be realized such as contactless distance and thickness measurements of multilayered dielectrics. Recently, we have presented a signal model based approach for the highly accurate inspection of multilayers which benefits both from frequency and phase information. In this contribution, we derive the theoretical minima of the distance and thickness variances directly considering the dependency of frequency and phase. These limits are compared with simulation and measurement results, applying different signal processing techniques. The highest precision is achieved by our signal model based correlation approach.