Phase-Gradient Huygens’ Metasurface Coatings for Dynamic Beamforming in Linear Antennas

Abstract

The beamforming capabilities of conformal cylindrical Huygens metasurface (HMS) coatings for linear antennas are assessed. It is shown that by engineering the phasegradient profile of the HMS, the original omnidirectional radiation pattern of the linear antenna can be shaped to form multi-or single-beam configurations. A closed-form expression for the phase-insertion profile of the cylindrical coating required to achieve the desired radiation pattern profile is derived, and several full-wave numerical examples supporting our claims are reported.A configuration exploiting a realistic HMS layout is also discussed and it is shown that, by making the metasurface reconfigurable through the use of tunable lumped elements, the radiated beams can be dynamically steered in space. This new design methodology could find application in smart electromagnetic environment scenarios for dynamically rerouting the signal towards multiple users.

Array Synthesis of Circular Huygens Metasurfaces for Antenna Beam-Shaping

“…Moreover, in this scenario, the maximum directivity value analytically evaluated is 6.72dB, whilst the directivity value of the secondary lobes points towards 𝜙 0 = 135°/225° is 5.89dB. We remark that with the approach proposed in [16], it was not possible to accurately predict the directivity values obtained, as well as the magnitude and pointing directions of the side-lobes.…”

“…2b), full-wave simulations when considering a stacked configuration of impedance sheets typically used to properly collocate the electric and magnetic dipole moments ensuring forward propagation are implemented. Indeed, this configuration is the one considered in [16] and used as a reference. Considering a phase-insertion profile on the azimuthal plane, θ is assumed be 90° and by imposing periodic boundary conditions and considering Floquet modes excitation, the element pattern from the antenna source can be extracted.…”

“…In this section, we validate the presented antenna array model for a circular HMS, discussing three different array configurations. We compare the analytically derived results in terms of expected radiation patterns with the ones coming from the synthesis of the HMS through the ray-tracing approach presented in [16]. In the latter, the unit-cells are implemented in a full-wave EM simulation tool as subwavelength constituents of the cylindrical HMS coat.…”

“…Thanks to these exciting properties, in the last decade, HMSs have shown wide possibilities in modifying the electromagnetic wavefront and, among them, the design of phase-gradient metasurfaces for refracting in unconventional ways the incoming field is one of the most discussed [20]. More specifically, in [16], we have shown that thanks to their wavefronts manipulation capability, cylindrical HMS mounted around a wire antenna can transform the omnidirectional pattern into multiple beams pointing towards specific desired directions. Indeed, by properly designing a gradient HMS, it is possible to modify the phase-insertion on the H-plane of the wire antenna.…”

“…This solution is able to modify the original omnidirectional radiation pattern of a central linear antenna source acting on the precise control of the amplitude and phase of the output fields. [15], [16]. Indeed, HMSs consist of unitcells that guarantee the full transmission of the impinging field and full control over its phase through a proper combination of the electric and magnetic dipole moments [17], [18].…”