Multi-Layered Coating Metasurfaces Enabling Frequency Reconfigurability in Wire Antenna

Abstract

In this work, we introduce a conceptually new approach for designing frequency reconfigurable wire antennas based on the use of multi-layered wrapping metasurfaces. Specifically, we demonstrate that the complex-valued input impedance of a wire antenna can be tailored by engineering the electromagnetic characteristics of a coating metasurface and we discuss how this effect can be exploited for achieving wide-band frequency reconfigurability. We report the advantages and limitations of this approachespecially compared to conventional impedance matching techniques -and, as a relevant example, we discuss the design of a reconfigurable half-wavelength dipole. For this example, the coating metasurface consists of a three-layer capacitive structure loaded with varactor diodes. It is shown that the operative frequency band of the antenna can be dynamically and continuously shifted in a quite broad range of frequencies (2/3 octave bandwidth) while preserving the current distribution of the fundamental mode and the omnidirectional shape of its radiation pattern on the horizontal plane. The possibility to allocate the antenna service within continuous sub-bands of operation makes this solution particularly suited for cognitive radio systems.

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

“…Remarkably, the applications enabled by conformal cloaking metasurfaces have been even more expanded by utilizing non-linear electronic devices loading the metasurface and conceiving antennas and array systems exhibiting different radiation characteristics depending on the power level or even the signal waveform [37]- [41]. Finally, conformal metasurface shells have been also used for broadening or tuning the antenna's resonance frequency by a judicious variation of the wrapping metasurface response [42]- [44]. Compared to the previous approach, here, the wrapping metasurface is engineered to induce secondary currents onto the antenna, hence, perturbing the fundamental resonant mode and enabling the design of frequency-agile systems by equipping the metasurface with varactor diodes [44].…”

“…Finally, conformal metasurface shells have been also used for broadening or tuning the antenna's resonance frequency by a judicious variation of the wrapping metasurface response [42]- [44]. Compared to the previous approach, here, the wrapping metasurface is engineered to induce secondary currents onto the antenna, hence, perturbing the fundamental resonant mode and enabling the design of frequency-agile systems by equipping the metasurface with varactor diodes [44].…”

Array Synthesis of Circular Huygens Metasurfaces for Antenna Beam-Shaping

“…However, this may not always be a feasible or economically viable solution, due to the high costs of the acquisition of new sites, rental fees, maintenance and power supply [3]. Moreover, the massive densification of antennas and the changing operational scenarios, required the development of compact add-on solutions for adapting preexisting antennas [4]- [5].…”