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Polarimetric measurements of foliage and terrain at 225 GHz
Abstract
The ability of radars to detect and classify targets has been greatly enhanced by maturation of the theory and practice of radar polarimetry. Although a substantial body of polarimetric measurements of natural surfaces has been accumulated over the last several decades at microwave frequencies, researchers have only recently begun to establish a similar data base at millimeter wavelengths. As an extension of this work, we have developed a fully polarimetric 225 GHz radar capable of remotely characterizing the average Mueller matrix of natural surfaces at ranges up to 1 km. We describe two incoherent measurement techniques, one which uses four transmit polarizations to uniquely specify the Mueller matrix, and a second using five or more transmit polarizations that reduces measurement errors. Documentation of the radar design is presented along with a description of the various procedures used to calibrate the receiver and transmitter subsystems. This radar was used to study the polarimetric behavior of a variety of natural surfaces, including decidous and coniferous trees, grass and sand. The ability to discriminate between planophil trees (horizontally oriented leaves) and erectophil trees (vertically oriented leaves) based on the fraction of polarized power is established for near grazing incidence. Dry sand was found to be the least polarized of all targets studied, bud became much more highly polarized when wet. These measurements show a substantial sensitivity to fine-scale surface features, and suggest the application of such a radar to class of remote sensing problems not addressed by other sensors.
Subject Area
Electrical engineering|Remote sensing
Recommended Citation
Mead, James B, "Polarimetric measurements of foliage and terrain at 225 GHz" (1990). Doctoral Dissertations Available from Proquest. AAI9022717.
https://scholarworks.umass.edu/dissertations/AAI9022717