Electromagnetic Wave Theory & Remote Sensing 14 . 2 Remote Sensing with Electromagnetic Waves

Electromagnetic waves are studied with applications to microstrip antennas, 1'2 geophysical subsurface probing,3' 4 scattering from helical structures5 '6 and Smith-Purcell radiation from metallic gratings.7 Radiation and resonance characteristics of two coupled circular microstrip disk antennas are studied rigorously using numerical techniques, matched asymptotic analysis, and the newly developed Hankel transform analysis.1,2 The electromagnetic fields due to dipole antennas in a two--layer dissipative medium is solved using the quasistatic approximation. 3 The solutions in integral forms are calculated with brute force numerical integration methods, the multi-image approach with the steepest descent method, the normal mode approach with the residue method, and a hybrid approach with combinations of the above methods. Electromagnetic wave scattering from helical structures has been studied using the physical optics and modal approaches. The fields scattered by a thin wire helix of finite extent is investigated using physical optics and the geometrical theory of diffraction.5 The geometrical theory of diffraction result is obtained as a high frequency limit of the physical optics approximation by applying the saddle point technique to the integral representation of the physical optics field. The electromagnetic wave scattering by a tape helix of infinite extent is studied by using Floquet wave expansion for its guided modes and scattered fields.6 The Smith-Purcell radiation problem is solved taking into account the penetrable properties of metallic gratings.7 When an electron beam streams across the surface of a metallic grating, emission of electromagnetic radiation occurs. It is shown that maximum radiation occurs when the surface plasmon mode is excited.