Flat Gain Broadband Metasurface Antennas

Abstract

Modulated metasurface (MTS) antennas can provide a broadside pencil beam at the frequency where the cylindrical surface wave (SW) wavelength matches the period of the impedance modulation. For modulations with constant period, the mismatch between the SW wavelength and the period imposes a limitation on the gain-bandwidth product. However, this limitation can be overcome by shaping the local period as a function of the radial distance. Doing so, we generate an annular active region on the antenna aperture, where the SW-toimpedance interaction mainly occurs. Such active region moves from the antenna center to the circular rim as the frequency decreases. This paper shows that one can optimize the profile of the local periodicity function to obtain broadside pencil beams over large bandwidths, while preserving the flatness of the gain versus frequency response and a good stability of the phase center. The antenna performances so obtained are really unique for flat antennas based on printed technology. Finally, we present a simple formula for the product between average gain and bandwidth, which gradually blends into the already known expression for modulations with constant period. This formula establishes an absolute limit of the gain-bandwidth product, which only depends on the wavelength-normalized antenna radius at the central frequency.

Overlapped and sequential metasurface modulations for Bi-Chromatic beams generation

“…The best performance is obtained for the overlapped modulation case, especially for lower frequencies. Indeed, the sequential approach at f 1 =26GHz presents higher sidelobes due to both the spurious radiation of the non-active circular region and the annular shape of the active region (the Hankel transform of an annulus with uniform amplitude presents higher sidelobe levels and a narrower beam than from the equivalent circular area) [13]- [14]. Fig.…”

“…Nonetheless, MTS antennas are not necessarily narrow-band [12]. Indeed, it has been shown in [13]- [14] that their bandwidth may be significantly increased at the expense of reducing the aperture efficiency, while maintaining the GBWP limited by the average group-velocity over the band. However, in some specific applications (like satellite communications at Ka-band), rather than a large bandwidth, the same aperture must provide two separate sub-bands that sometimes are considerably separated from each other.…”

Modulated Metasurface Antennas with Enhanced Broadband Response

“…2 represents this step. The objective in-band average gain Gave is then selected and the aperture radius a is found using the formula [13] , 0 0 0 28.7 28.7…”

THz-photonics transceivers by all-dielectric phonon-polariton nonlinear nanoantennas

“…Regarding THz beam control, phased array devices, leaky-wave antennas, reflectarrays, and transmitarrays can often be suitable for ad hoc wavefront engineering. Noteworthy, metasurfaces are today identified as the common framework where all the above approaches can be conveniently unified 10 to provide a compact and integrable solution to a variety of different beam forming needs. For example, in Fig.…”