Polarimetric backscatter measurements of deciduous and coniferous trees at 225 GHz

Polarimetric radar measurements of foliage made in the 220-GHz transmission window are described. A noncoherent, 60-W-peak-power polarimetric radar was used to measure the target Mueller matrix directly by measuring the scattered polarization state for either four or six incident polarizations. Measurements of deciduous trees indicate that waves scattered from erectophil trees (vertically oriented leaves) are more highly polarized than waves scattered from planophil trees (horizontally oriented leaves) for near-grazing incidence angles. White pine trees, which have thin needles, where the least polarized of all trees studied. A comparison of the Mueller matrices of 11 independent footprints taken from seven white pine trees showed a high degree of consistency between measurements