Transformation Electromagnetics for Antenna Applications
In recent years, transformation electromagnetics has found potential applications in propagation, waveguiding, scattering, and radiation. For antenna applications, using transformation techniques, one can transform bulky antennas to low profile ones. In general, the resulting medium will be both inhomogeneous and anisotropic. In this chapter, we proposed a spherical core-shell structure which can achieve arbitrarily large directivity. We investigated the problem by finding the transformed constitutive tensors and solving the equivalent problem in the core-shell configuration. Using the Ricatti-Bessel functions, we can represent the field components with Debye potentials and subsequently solve for the fields in all regions. We applied the formulation to several cases of dipole arrays within the shell, corresponding to both free-space and half-space problems in the virtual space. Overall, the calculation demonstrated that the formation of virtual aperture is indeed theoretically possible and the effects of loss on the number of available spherical harmonics and directivity are investigated.
KeywordsCompression Ratio Transmission Coefficient Loss Tangent Virtual Space Constitutive Parameter
This work is in part supported by the Air Force Office of Scientific Research.
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