Absolute wighting functions for near-field microwave radiometric applications

Microwave radiometry is being used in order to measure the subsurface tempe rature in lossy materials-such as living tissues-from the near-field therma l noise emitted in the microwave frequency range. Efforts have been ongoing during the past years to well determine and to increase the volume of the material coupled to the probe. This article discusses a new definition of t he near-field weighting functions for microwave radiometric signals and exa mines its impact on diagnostic performance of several applications. A metho d is also proposed to improve the knowledge of the weighting functions from an estimation of the backward signals in the air surrounding the probe in active process.