Compact Double-Layer FR4-Based Focusing Lens Using High-Efficiency Huygens’ Metasurface Unit Cells

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.

A Single-Layer Focusing Metasurface Based on Induced Magnetism

“…Table 2 compares the important performance indicators of the proposed metasurface with the six reported metasurfaces. The single-layer design with vias [22], double-layer type [26,28], and triple-layer type [27] fulfill high efficiency and full phase shift at the price of complex structure and expensive fabrication. We use a single-layer design without vias to achieve a full phase shift of 2π and high transmission amplitude, which effectively improves the focusing efficiency of the metasurface.…”

Real-Time Metasurface Sensor for Monitoring Micropoisons in Aqueous Solutions Based on Gold Nanoparticles and Terahertz Spectroscopy

“…The measurement system is based on a combination of an advanced CW frequency-domain terahertz spectrometer and a perfect absorber metasurface (MS) sensor coated with a thin layer of gold nanoparticles. The perfect absorber metasurface [ 12 , 13 ] was fabricated on double-sided FR4 substrate using printed board circuit (PCP) technology, which is very inexpensive (see Figure 1 ) [ 14 ]. The resonance frequency, f res , of the perfect absorber is determined according to the geometrical metal shape dimensions and the dielectric constant of the substrate (see Equations (1)–(4)).…”

“…The resonance frequency, f res , shift due to the presence of micropoisons is measured using a high-resolution compact terahertz CW frequency-domain spectrometer. was fabricated on double-sided FR4 substrate using printed board circuit (PCP) technology, which is very inexpensive (see Figure 1) [14]. The resonance frequency, fres, of the perfect absorber is determined according to the geometrical metal shape dimensions and the dielectric constant of the substrate (see Equations ( 1)-( 4)).…”

Gradient Index Metasurface Lens for Microwave Imaging

“…Classic examples of GRIN lenses include the Fresnel lens, Wood lens and Luneburg lens [ 40 , 41 , 42 , 43 ]. The advent of metamaterials and metasurfaces has renewed interest in research of GRIN lenses and inspired numerous works [ 44 , 45 , 46 , 47 , 48 , 49 , 50 ]. The tailorable properties and flat geometry of metasurfaces has provided ground-breaking engineering potential for GRIN lens designs, which was not possible with conventional dielectrics.…”