Planar metal-only omnidirectional retroreflector using transmitarray and blazed grating for TE and TM polarizations

Area of Science:

• Electromagnetics and Metamaterials
• Microwave Engineering
• Optics and Acoustics

Background:

• Existing retroreflectors are often bulky, uneven, and unsuitable for large structures.
• Previous planar retroreflectors at microwave frequencies were limited to non-planar designs, lacked omnidirectional coverage, and supported only TM polarization.

Purpose of the Study:

• To propose a novel planar and metal-only retroreflector for microwave frequencies.
• To achieve omnidirectional retroreflectivity for both TE and TM polarizations.
• To overcome the bulkiness and polarization limitations of existing retroreflector designs.

Main Methods:

• A two-layer cascaded structure was designed, featuring a transmitarray top layer and a reflective bottom layer.
• The bottom layer was implemented using either a spatially varying blazed grating or a spatially varying phase gradient metasurface.
• Simulations and measurements were performed to validate the retroreflector's performance.

Main Results:

• The proposed retroreflector demonstrates efficient, omnidirectional reflection of electromagnetic waves in both TE and TM polarizations.
• The first type, utilizing a blazed grating, achieved a 60° elevation field of view and 63% normal incidence efficiency at 10 GHz.
• The second type, a phase gradient metasurface, offered higher monostatic radar cross-section (RCS) for TE polarization.

Conclusions:

• The novel planar retroreflector design effectively addresses the limitations of previous technologies.
• The proposed structure offers a compact and versatile solution for omnidirectional retroreflection at microwave frequencies.
• The demonstrated performance validates the potential of this design for various applications requiring efficient wave reflection.