Combinations of low/high permittivity and/or permeability substrates for highly directive planar metamaterial antennas

Abstract

An investigation of planar metamaterial antennas consisting of grounded metamaterial substrates with low and/or high values of the electric permittivity and/or the magnetic permeability excited by dipole sources is presented. Their performances are characterised in terms of their capability to radiate high levels of power density in the broadside direction and to produce narrow pencil beams pointing at broadside with high directivity. To achieve a high directivity, a pair of weakly attenuated cylindrical leaky waves is excited along the metamaterial substrate; sufficient conditions are established for the existence of such leaky waves in terms of the values of the substrate permittivity and permeability. Approximate closed-form expressions are derived for the phase and attenuation constants of the leaky waves. Numerical results are given in order to illustrate the radiative features of this class of antennas and to validate the theoretical analysis.

Towards an experimental realization of affinely transformed linearized quantum electrodynamics vacuum via inverse homogenization

“…2-4, are not at all infeasible. Indeed, present-day technology allows for the possibility of materials with a considerably wider range of constitutive parameters to be engineered [20,21,22]. …”

Directive Leaky-Wave Radiation From a Dipole Source in a Wire-Medium Slab

“…In [25] we have compared the leaky-wave model with a pure geometrical-optics analysis. In [26] we have shown the combinations of permittivity-permeability that give rise to high directivity, whereas in [27] a figure of merit has been introduced to compare radiators based on these metamaterial structures with more standard Fabry-Pérot antennas.…”

Broadside radiation enhancement using a spiral resonator MNZ metamaterial substrate

“…In fact, in the presence of large values (or even negative values) of the effective magnetic permeability, a wave impinging on such structures experiences a strong reflection. However, AMMs can also offer a Mu-Near-Zero (MNZ, i.e., 0 < Re[µ r ] << 1) band of operation, which can be of interest in broadside radiation enhancement [3]. Several design guidelines have been presented in [3], in order to obtain a grounded metamaterial slab for enhanced broadside radiation, by either using an ENZ or an MNZ substrate, that correspond to high and low impedance substrates, respectively.…”

“…The power density radiated at broadside (θ = 0º) can be expressed as [3]: . It is worth noting that, when the slab thickness is chosen as h opt = λ 1 /4 (with λ 1 = λ 0 /n r ), the broadside power density is maximum.…”