SCATTERING OF ELECTRIC DIPOLE RADIATION BY A MOVING, DISPERSIVE DIELECTRIC HALF-SPACE
WASHINGTON UNIV SEATTLE DEPT OF ELECTRICAL ENGINEERING
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The problem of a point electric dipole moving over a dispersive dielectric half-space is studied. The dipole is located in the free space above the dielectric and is assumed to be time harmonic in its rest frame, oriented perpendicular to the interface and moving parallel to it. Previous work in this area has been mostly confined to the use of a plane wave as a source or a non- dispersive dielectric. Solutions for this problem are obtained using integral transform techniques. The integration is performed for the free space region by making an asymptotic expansion for one integration and then using the saddle point approximation for the remaining integration. The solution obtained in this manner for the vector potential is then used to generate the electric and magnetic fields in both the rest frame of the source and the rest frame of the dielectric. This yields the reflected radiation fields for the case of an arbitrary, dispersive dielectric and the lateral wave fields and surface wave fields for the case of a lossless plasma. The field patterns are distorted by the relative motion of the source and dielectric. In the rest frame of the source, all three waves exhibit the frequency of the source and in the rest frame of the dielectric, they all exhibit some form of Doppler shift different from the primary wave. The criteria for existence of the lateral wave is not modified by the relative motion of the source and dielectric but the criteria for existence of the surface waves is greatly modified by the relative motion. For velocities greater than some critical velocity, a new type of surface wave comes into existence.
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