The possibility of generating a higher-order non-diffracting Bessel beam by means of a fast backward spatial harmonic is discussed in this work. The focusing features of the radiated near field are achieved by the excitation of a higher-xorder cylindrical leaky wave supported by an annular metal-strip grating placed on a grounded dielectric slab, which is excited by a circular arrangement of elementary sources.
The classical problem represented by a planar thin conductive shield in the presence of vertical dipole field sources (electric or magnetic) is solved analytically in the time domain via the Cagniard-de Hoop technique. Comparisons with numerical solutions carried out by means of efficient integration algorithms are provided and discussed.
The electromagnetic problem of calculating the pulsed radiation from a horizontal magnetic dipole in the presence of a planar thin conductive screen is solved analytically in the time domain via a modified Cagniard-de Hoop approach. The components of the relevant time-domain electric and magnetic dyadic Green's functions are expressed by simple one-dimensional integrals over a finite integration domain. Expressions for the transient electromagnetic fields can thus easily be obtained and numerical results are provided that illustrate the main time-domain shielding characteristics.
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