Electromagnetic Scattering in Microwave Remote Sensing and Fluctuation Electrodynamics

Abstract

Application of the electromagnetic scattering theory to the physical models of microwave remote sensing of natural targets including but not limited to polar ice sheets, soil surface, vegetated area, etc. and fluctuation electrodynamics as well as microwave resonators are presented in this thesis. Advancement of the remote sensing technology led the radar and radiometry measurement to a level of accuracy that correct interpretation of the measurement outcomes and relating those to the unknown parameters under study requires the physical models that are capable of resembling the real life situation as close and accurate as possible. Along with accuracy, the model should be simple enough for the purpose of real time implementation. This is where the analytical solution of the physical problem manifest itself against pure numerical methods in terms of the fast evaluation and more importantly the insight that is not available in a numerical approach. Scattering from random rough interferences is studied throughout the first part of the thesis. Also, beyond the small perturbation method, the T-matrix method is also studied as an alternative approach that works for larger surface heights. Beside these, an alternative partially coherent approach is also introduced to significantly reduce the computational cost of the problem of layered media with random permittivity profile. The finite coherency length of the propagating wave inside the layered media is considered to divide the layered media into smaller blocks and then combine the block's responses afterward. In the second part we consider fast and broad band computation of the Green's function inside the cavity of irregular shape. Conventional way of computing the Green's function of an irregular shaped cavity is the numerical methods such as surface integral equation or finite element methods which can obtain the response at single frequency with intensive computational cost. The proposed method utilizes the imaginary wave number extraction of the Green's function from itself to develop a broad band and at the same time fast converging hybrid spatial-spectral expansion to achieve a highly accurate result for the Green's function whereas in computing the Green's function of cavity using numerical methods, a fine sweep over the frequency band is required to capture individual resonance line, the broad band solution provide the solution thousand times faster than the competitor methods. The last part of the thesis includes a classical electromagnetic treatment of the Casimir self-stress on nano tubes. Although the Casimir force on the parallel plates can be regularized by throwing away the bulk part of the full Green’s function, it is shown that such a regularization does not remove divergence of zero-point energy and the final stress is computed by applying further regularizations.