Information Extraction from Polarized MMW Radiation Based on the Weak Correlation between Emission and Reflection

Millimeter-wave (MMW) radiometry has been used in a vast and growing assortment of applications. Several MMW discriminators have been proposed and achieved good results in material classification and recognition. However, these discriminators are difficult to measure accurately in the real world. In this article, we defined two discriminators, emissive degree of polarization (EDoP) and reflecting DoP (RDoP), and proposed a physically based method using the characteristic of weak correlation of the emission part and reflection part of MMW radiation as an optimization criterion to obtain the optimal estimation of RDoP. Most measurement errors, such as the thermal noise of the radiometer, radiative transfer, antenna pattern, and calibration error, will not affect our method, and thus it is easy to implement in the real world. The effectiveness of our method has been verified by experiments. Our method only needs to measure the brightness temperature of horizontal polarization and vertical polarization. Based on RDoP, more information such as other discriminators, physical temperature, equivalent permittivity, reflectivity, and surrounding brightness temperature can be retrieved. Potential applications include liquid ingredient analysis, terrain monitoring, and security checks.