High-Efficiency Refracting Millimeter-Wave Metasurfaces

Abstract

Printed circuit metasurfaces have attracted significant attention in the microwave community for their capability of versatile wavefront manipulation. Despite their promising potential in telecommunications and radar applications, few transmissive metasurfaces have been reported operating at millimeter-wave frequencies. Several secondary effects including fabrication tolerances, interlayer near-field coupling and the roughness of conductors are more severe at such high frequencies and can cause significant performance degradation. Additionally, experimental characterization techniques reported previously are not accurate enough for the verification of such effects. In this work, we present highly efficient refracting metasurfaces operating at 83 GHz. We use a sophisticated synthesis technique that minimizes possible effects of performance degradation such as interlayer near-field coupling and the influence of fabrication tolerances. Additionally, we propose a new experimental technique for the characterization of periodic metasurfaces. Using this technique, we present for the first time an accurate determination of the intensity of propagating Floquet harmonics in a broad frequency range. The proposed method gives deep insight into the beam refraction problem as it accurately quantifies in which direction energy is scattering. Additionally, it verifies our numerical model.

Huygens Metasurface Lens for W-Band Switched Beam Antenna Applications

“…We aim to achieve a high transmission efficiency at the center frequency and we want to maintain compatibility with commercial printed circuit board (PCB) processes. Therefore, we utilize a Huygens metasurface architecture with three metallic layers spaced by dielectrics, similar to previous work [32], [33], [37]. The dielectric substrate Isola Astra MT has a relative permittivity of 3.0 and a loss tangent of 0.0017 and it allows us to space the metallic layers by 254 µm.…”

“…For the same reason, metallic shapes are designed with an edge radius of > 30 µm. More detailed information on this high frequency meta-atom design are found in [33].…”

“…[32]. With this method, secondary effects that can cause performance degradation, such as inter-layer near-field coupling and losses induced by copper roughness, are minimized [33].…”

“…In this part of the spectrum, the design and experimental characterization of highly transmissive metasurfaces is particular challenging [5], [6], [13]. For efficient Huygens type mm-wave metasurfaces consisting of three metallic layers, effects such as inter-layer near-field coupling [32], losses caused by conductor roughness [33], [34] and frequency shifts due fabrication tolerances are significant and have to be considered in the design.…”

“…Recently, we reported a novel synthesis method which incorporates near-field coupling and conductor roughness, minimizing such effects in an iterative optimization algorithm [32]. With this numerical method, highly efficient refracting mm-wave metasurfaces were experimentally demonstrated by extracting the intensity of Floquet harmonics from far-field measurements [33]. However, the design and experimental characterization of a non-periodic metasurface lens requires detailed near-field measurements [15], [35], [36].…”