Simplified Reflection-Based Calibration for a Multistatic Microwave Imaging System

This work presents a simplified calibration procedure for multistatic microwave imaging systems that uses both the time-domain reflection signatures of the entire system and an extended two-port calibration in an auxiliary channel to correct temporal drifts and align the measurement reference planes with the inversion kernel. This approach substantially reduces the experimental burden and complexity of a standard full calibration and allows for continuous calibration without hardware setup intervention during measuring campaigns. Its performance is experimentally tested on a single-ring eight-antenna system, with two groups of four antennas, each connected to a one-pole-four-through RF switch, and a simplified cylindrical phantom that mimics the average dielectric properties of human head tissues. For imaging, a multi-frequency bi-focusing algorithm is employed, yielding a noticeable improvement over the uncalibrated case, as evaluated by various metrics.