Towards millimetre-wave spectroscopy of human blood using an open-ended waveguide

Broadband dielectric spectroscopy of blood above 50 GHz is scarce due to hardware limitations, affordability, and complexity. This study explores the use of a rectangular waveguide as a probe for analysing human blood in the 55 to 95 GHz range, at temperatures from 23 °C to 36 °C, and Haemoglobin levels between 0 and 16 g/dL, focusing on practical aspects such as sample preparation and the setup’s mechanical, thermal, and calibration requirements. The research highlights the effectiveness of the Short-Open-Load calibration method, evidenced by precise measurements of saline solutions. Furthermore, analysis of 84 human blood samples indicates that while Haemoglobin levels introduce some uncertainty in dielectric constant measurements, dielectric loss readings remain consistent across temperature and Haemoglobin variations, with a low uncertainty of under 2.65%, indicating the potential use of this parameter in future millimetre-wave techniques for non-invasive testing of blood analytes. • Open-ended waveguide allows dielectric characterisation of fluids above 50 GHz. • Time critical reducing dielectric effects caused by Erythrocyte Sedimentation Rate. • Blood’s dielectric loss more sensitive to haemoglobin changes than dielectric constant. • Higher haemoglobin content dampens dielectric constant changes caused by temperature.