Compact Acoustic Retroreflector Based on A Mirrored Luneburg Lens

TL;DR

This paper introduces a compact acoustic retroreflector using gradient index metamaterials based on a mirrored Luneburg lens, capable of redirecting signals efficiently over a broad angular range and bandwidth.

Contribution

It presents a novel, miniaturized acoustic retroreflector design based on GRIN metamaterials with experimental validation of its performance.

Findings

Operates effectively within 120-degree incident angles

Works over a bandwidth of approximately 27% of the central frequency

Has a size of about one wavelength, demonstrating compactness

Abstract

We propose and demonstrate a compact acoustic retroreflector that reroutes probing signals back towards the source with minimal scattering. Gradient refractive index (GRIN) acoustic metamaterials, based on Archimedean spiral structures, are designed to fulfill the required refractive index profile. The experiments show that the compact acoustic retroreflector, whose radius is only approximately one wavelength, works in an incident angular range up to 120 degrees over a relatively broad bandwidth of about 27% of the central frequency. Such compact acoustic retroreflectors can be potentially applied in pulse-echo based acoustic detection and communication, such as unmanned aerial vehicle (UAV) sonar systems, robotic ranging detectors, ultrasonic imaging systems.