A liquid crystal based tunable polarization selector in a microwave imaging radiometer

Polarimetrie measurements, i.e. the analysis of electromagnetic waves with respect to their polarization, is of interest in remote sensing applications to analyze materials or to increase the visual quality of imaging technologies. One well known application in the optical domain is the polarizing filter used by photographers to reduce unwanted reflections or to increase sky contrast. In this paper, the application in the microwave domain is studied on a microwave imaging radiometer combined with an electrically tunable polarization selector based on liquid crystal. With this setup, radiometric images of a car have been captured for different polarization angles. By this, the polarimetric properties of some car features can be observed. Further, a reaction time measurement has been conducted for the utilized polarization selector, showing stable polarization states after 100 s and 250 s depending on the polarization state.