Abstract
High transmission efficiency metasurface unit cells have been designed based on surface electric and magnetic impedances derived from Huygens’ principle. However, unit cells for low transmission loss (<1 dB) over a wide transmission phase range require at least three metallic layers, which complicates the unit cell design process. In this paper, we introduce high-efficiency Huygens’ metasurface unit cell topologies in double-layer FR4 printed circuit board (PCB) by implementing surface electric and magnetic current using the top and bottom metallic patterns and via drills. Eleven unit cells were optimized for wide phase coverage (−150° to 150°) with a low average transmission loss of −0.82 dB at 10 GHz. To demonstrate the high-efficiency of the designed unit cells, we designed and fabricated two focusing lenses with dimensions of near 150 × 150 mm (5λ × 5λ) to focus a spherical beam radiated from short focal distances (f = 100 and 60 mm). The fabricated focusing lens showed 12.87 and 13.58 dB focusing gain for f = 100 and 60 mm at 10 GHz, respectively, with a 1 dB fractional gain bandwidth of near 10%. We expect that the proposed focusing lens based on high-efficiency double-layer metasurface unit cells can help realize compact and high-gain focusing lens-integrated antenna systems.
Highlights
Metasurface is a two-dimensional structure with subwavelength particles or unit cells for manipulating propagation direction [1,2,3,4,5], polarization [6,7,8,9,10,11], and orbital angular momentum (OAM) [12,13,14,15] of electromagnetic (EM) waves
After the advent of a popular metasurface design using the generalized Snell’s law [1], which deals with a phase gradient on the surface, Huygens’ principle was utilized to improve the efficiency of wave-refracting metasurfaces by introducing surface electric and magnetic currents [2]
Metasurface design based on Huygens’ principle is theoretically sound; it is not straightforward to implement electric and magnetic surface impedances that cover a wide transmission phase range with high transmission efficiency in a planar 2D structure, e.g., printed circuit board (PCB)
Summary
Metasurface is a two-dimensional structure with subwavelength particles or unit cells for manipulating propagation direction [1,2,3,4,5], polarization [6,7,8,9,10,11], and orbital angular momentum (OAM) [12,13,14,15] of electromagnetic (EM) waves. Using Huygens’ principle, a metasurface was modeled as a two-dimensional boundary and the required electric and magnetic surface impedances to control the propagation direction of a transmitted wave were achieved [2]. Metasurface design based on Huygens’ principle is theoretically sound; it is not straightforward to implement electric and magnetic surface impedances that cover a wide transmission phase range with high transmission efficiency in a planar 2D structure, e.g., printed circuit board (PCB). We introduce double-layer metasurface unit cells with high transmission efficiency and wide phase coverage at 10 GHz by constructing electric and magnetic dipole structures based on Huygens’ principle.
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