# A Surface Impedance-Based Three-Channel Acoustic Metasurface Retroreflector

## TL;DR

This paper introduces a compact, efficient acoustic retroreflector using a surface impedance model and diffraction, capable of retroreflecting at three specific incident angles for advanced sensing and communication applications.

## Contribution

It presents a novel impedance-based design for a three-channel acoustic retroreflector that operates at discrete angles with high efficiency and minimal parasitic diffraction.

## Key findings

- Achieves retroreflection at -60°, 0°, and 60° incident angles.
- Uses a periodic grating to realize surface impedance.
- Thickness is about half the wavelength, ensuring compactness.

## Abstract

We propose the design and measurement of an acoustic metasurface retroreflector that works at three discrete incident angles. An impedance model is developed such that for acoustic waves impinging at -60 degrees, the reflected wave is defined by the surface impedance of the metasurface, which is realized by a periodic grating. At 0 and 60 degrees, the retroreflection condition can be fulfilled by the diffraction of the surface. The thickness of the metasurface is about half of the operating wavelength and the retroreflector functions without parasitic diffraction associated with conventional gradient-index metasurfaces. Such highly efficient and compact retroreflectors open up possibilities in metamaterial-based acoustic sensing and communications.