Simplified Multi-Channel Calibration for Microwave Imaging Systems

This work proposes and validates a simplified n-channel calibration for microwave imaging systems that reduces the complexity of a standard full-port calibration from a minimum of 4n − 1 measurements to 4(2) − 1 ones, respectively. The method consists of a joined 2-port standard calibration with a multi-port extrapolation. It compensates for systematic errors and mitigates the effects of losses and phase shifting caused by the multiplexing stage of a microwave imaging system. The conditioning and limitations of the technique are studied, including the switching matrix’s dynamic range, insertion loss, and the error path extrapolation analysis. Finally, the calibration is validated by employing a brain stroke monitoring system using either an electromechanical switching matrix or a solid-statebased one, and repeatability and stability tests that demonstrate the calibration’s effectiveness and robustness are performed.