Optimization Algorithms for Accurate FMCW Millimeter Wave and Terahertz Thickness Measurements

We utilize the frequency-modulation continuous-wave (FMCW) approach to measure multilayer thicknesses using millimeter wave and terahertz transceivers. The bandwidth limits the resolution but can be extended by model-based signal processing. The solution space is characterized by numerous local optima. We compare the potential of different optimization algorithms to replace the computational expensive brute force approach. Variants of gradient descent and Nelder-Mead simplex algorithm are presented utilizing information of the solution space. We compare the results with the ones of a genetic algorithm.