研究目的
To develop a broadband metasurface Luneburg lens capable of full-angle operation with simplified fabrication and improved performance.
研究成果
The proposed metasurface Luneburg lens successfully achieves broadband full-angle operation with simplified fabrication using PCB techniques. It demonstrates good agreement between simulations and measurements, with high efficiency (up to 62% in simulation, 44% in measurement at 7.9 GHz) and low phase aberrations. The use of size-variable meta atoms and ISPPW structure provides better approximation to the ideal refractive index profile and circular symmetry, making it suitable for applications like full-angle scanning and multi-beam routing.
研究不足
The fabrication process may have imperfections such as flatness issues with the aluminum plate and soldering defects, leading to deviations between simulated and measured results. Radiation losses increase with frequency, reducing efficiency. The tapered microstrip ports are not ideal point sources, causing phase aberrations and mutual coupling. The quasi-TEM characteristics may degrade with very high permittivity substrates, not explored in this study.
1：Experimental Design and Method Selection:
The design uses an inverted substrate parallel-plate-waveguide (ISPPW) structure with nonuniform circular holes etched on the upper metallic plate to create a metasurface. Size-variable meta atoms are employed to achieve a smooth gradient refractive index profile and circular symmetry. Tapered microstrip ports are distributed around the lens circumference for full-angle operation.
2：Sample Selection and Data Sources:
A prototype lens with a diameter of 400 mm is fabricated and tested. Simulations are conducted using CST Microwave Studio to model electromagnetic behaviors and extract effective refractive indices.
3：List of Experimental Equipment and Materials:
Equipment includes a network analyzer for measurements, SMA connectors, aluminum ground plate, Rogers 4350B substrate (εr =
4：48, tanδ = 0037), nylon gaskets, and soldering tools. Materials include the fabricated lens and tapered microstrip ports. Experimental Procedures and Operational Workflow:
The lens is fabricated using PCB techniques. Measurements involve connecting one port as a feed and others as outputs or isolations, with terminated loads to avoid reflections. S-parameters are measured across 6-9 GHz.
5：Data Analysis Methods:
Effective refractive index is extracted from S-parameters using an inversion method. Transmission amplitudes, phase aberrations, return losses, and power distributions are analyzed to evaluate performance against simulations and ideal lens models.
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