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Artificial Inhomogeneous Tapered Impedance Sheet Characterization and Applications
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT
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The ability to manipulate a complex impedance sheet about a PEC or general dielectric cylinder of arbitrary diameter to control the overall scattering characteristics at particular angles for shielding or scattering applications is presented. It is shown that with the capability to readily control both the real and imaginary components of a percolated lossy films effective impedance, specific impedance distributions can be obtained to effectively direct the overall nulls in the bistatic scattering pattern. The exact approach only requires negligible truncation error of the matrix solution and can be applied to cylinders of arbitrary size. This approach relies on general impedance sheet boundary conditions in addition to a Fourier series representation of the impedance sheet distribution, with the utilization of Wronskian and recurrence relations, to produce a computationally efficient matrix solution for the scattered field expansion coefficient an. This scattering coefficient an can then be included in the expression for a two-dimensional scattering width, allowing for the computation of scattering patterns of arbitrary diameter cylinder impedance sheet distributions. The ability to adapt sheet impedances to effectively control the overall nulls in the bistatic scattering pattern will be demonstrated, with practically-implemented impedance characteristics. Lastly, a novel rectangular X-band waveguide system will be utilized to characterize the electromagnetic properties of the phi-dependent impedance sheet.
APPROVED FOR PUBLIC RELEASE