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

Area of Science:

• Metamaterials and Nanophotonics
• Electromagnetics and Microwave Engineering
• Printed Circuit Board (PCB) Technology

Background:

• Designing high transmission efficiency metasurface unit cells often requires complex multi-layer structures.
• Achieving low transmission loss (<1 dB) across a wide phase range typically necessitates at least three metallic layers.
• This complexity hinders practical fabrication and integration of metasurface devices.

Purpose of the Study:

• To introduce novel, high-efficiency Huygens' metasurface unit cell topologies.
• To simplify metasurface design using a double-layer printed circuit board (PCB) approach.
• To demonstrate the performance of these unit cells in focusing lens applications.

Main Methods:

• Developed double-layer metasurface unit cells on FR4 PCB using top/bottom metallic patterns and via drills.
• Implemented surface electric and magnetic currents for impedance control.
• Optimized eleven unit cells for wide phase coverage (-150° to 150°) and low transmission loss at 10 GHz.

Main Results:

• Achieved wide phase coverage with a low average transmission loss of -0.82 dB at 10 GHz.
• Fabricated two focusing lenses (near 5λ × 5λ) demonstrating high focusing gains of 12.87 dB and 13.58 dB.
• Obtained a 1 dB fractional gain bandwidth of approximately 10% for the focusing lenses.

Conclusions:

• The proposed double-layer Huygens' metasurface unit cells offer high efficiency and simplified design.
• The developed focusing lenses demonstrate excellent performance for short focal distance applications.
• This technology holds potential for realizing compact, high-gain antenna systems with integrated focusing lenses.