Microwave antenna array calibration via simulated and measured S-parameters matching

This paper extends the validation of an innovative calibration framework for microwave imaging systems combining measured scattering parameters with numerically simulated ones. The aim is to improve the imaging operator accuracy by overcoming possible variations between the measurement system and its numerical model. Here, we investigate the possibility of reconstructing the transmission coefficients, measured at the antenna ports, employing a custom set of simulations where manufacturing tolerances are introduced. The experimental validation considers a microwave antenna array designed for brain imaging; each antenna is immersed in a brick of custom coupling medium whose dielectric properties variability is mainly analyzed. Further, the simulated dataset is provided by a high-fidelity full-wave electromagnetic tool, based on the finite element method, and coupled with a 3-D CAD model. This work presents an essential step forward in the whole calibration scheme, to then be able to estimate the electric field within the domain of interest, thus improve the imaging operator.