Broadband resonant calibration-free complex permittivity retrieval of liquid solutions

•Material susceptibilities govern interactions between electromagnetic waves and matter and are of a crucial importance for basic understanding of natural phenomena and for tailoring practical applications.•Here we present a new calibration-free method for relative complex permittivity retrieval, which allows using accessible and cheap apparatus and simplifies the measurement process.•The method combines advantages of resonant and non-resonant techniques, allowing to extract parameters of liquids and solids in a broad frequency range.