Polarimetric properties of land clutter at millimeterwave bands

To have an appropriate data base for the development of non-cooperative target identification techniques, airborne measurements were conducted with the mmW-SAR-system MEMPHIS over agricultural terrain with a variety of different fields and canopies of trees. Four different depression angles were used, ranging between 15° and 38°, which allows to determine important clutter parameters as a function of depression angle. During the measurements evaluated here, the transmit polarization was switched from pulse to pulse between horizontal and vertical. Most important for a comparison between different passes is a careful polarimetric calibration. This was done using a statistical method. Absolute amplitude calibration was achieved by means of trihedral corner reflectors. The SAR processing provides the user with several degrees of freedom. Apart from different cross range (Doppler) resolution cell sizes it is possible to create either single look or multi-look images and study the influence of averaging on reflectivity statistics. The results are valuable not only for discrimination and ATR algorithms but also for the development of polarimetric target/clutter simulation models.The paper describes the experimental set-up and discusses the evaluation methods. Typical results are presented and the implications on ATR methods are highlighted.