Exploiting the leaky-wave properties of transmission-line metamaterials for single-microphone direction finding

Abstract

A transmission-line acoustic metamaterial is an engineered, periodic arrangement of relatively small unit-cells, the acoustic properties of which can be manipulated to achieve anomalous physical behaviours. These exotic properties open the door to practical applications, such as an acoustic leaky-wave antenna, through the implementation of radiating channels along the metamaterial. In the transmitting mode, such a leaky-wave antenna is capable of steering sound waves in frequency-dependent directions. Used in reverse, the antenna presents a well defined direction-frequency behaviour. In this paper, an acoustic leaky-wave structure is presented in the receiving mode. It is shown that it behaves as a sound source direction-finding device using only one sensor. After a general introduction of the acoustic leaky-wave antenna concept, its radiation pattern and radiation efficiency are expressed in closed form. Then, numerical simulations and experimental assessments of the proposed transmission-line based structure, implementing only one sensor at one termination, are presented. It is shown that such a structure is capable of finding the direction of an incoming sound wave, from backward to forward, based on received sound power spectra. This introduces the concept of sound source localization without resorting to beam-steering techniques based on multiple sensors.

Topological acoustic polaritons: robust sound manipulation at the subwavelength scale

“…In addition, our system is opened to its environment, and by operating within the sound cone, topological acoustic states can be coupled to the radiation continuum. This opens interesting application perspectives for topological acoustic polaritons, which may enable disruptive advances in transducer or sensing technologies, including a new generation of topologically protected acoustic leaky wave antennas [73][74][75][76] and subwavelength imaging systems [67]. In addition, the slow group velocity of topological acoustic polaritons may be of significant interest to realize robust slow wave systems, avoiding their typical sensitivity to disorder.…”

Improving directional radiation quality based on a gradient amplitude acoustic leaky wave antenna

“…Acoustic directional radiation is crucial in many areas such as acoustic integrated and detection devices [1,2]. Acoustic leaky wave antennas (ALWAs) as a type of passive antennas possess the capability of directional radiation scanning as a function of the incident frequency [3][4][5][6][7]. Although phased-array antennas are also effective at acoustic steering, the presence of numerous active elements leads to high costs of construction and significant power requirements.…”

“…The ALWA constructed by CRLH-TL metamaterial will allow the wavenumbers to continuously vary from negative to positive, and the main radiation beam scans from backward to forward [−90°:90°] as a function of the incident frequency [4]. In previous studies, the CRLH-TL ALWAs have been designed using an array of side holes and membranes that were periodically loaded along the waveguide, where power could leak along the waveguide through the periodical side holes [5][6][7]. So far, acoustic antennas have attracted considerable attention because they exhibit various unique applications, such as single sensor direction-finding [7], acoustic dispersive prisms [8], sound source localization [9] and noise control [10][11][12].…”

“…In previous studies, the CRLH-TL ALWAs have been designed using an array of side holes and membranes that were periodically loaded along the waveguide, where power could leak along the waveguide through the periodical side holes [5][6][7]. So far, acoustic antennas have attracted considerable attention because they exhibit various unique applications, such as single sensor direction-finding [7], acoustic dispersive prisms [8], sound source localization [9] and noise control [10][11][12]. Despite the tremendous prospect of these devices with acoustic steering, they will unavoidably bring many side lobes with the increase of unit cell number and size.…”

Development of leaky-wave antenna applications with acoustics metamaterials: From the acoustic dispersive prism to sound direction finding with a single microphone

“…In the same time, a dedicated mounting system was proposed to assemble the Kapton membranes inside the host waveguide, so that their mechanical impedance alignment can be ensured. Thanks to this innovative design, the first Acoustic Dispersive Prism (ADP) has been achieved [5], together with the dual concept of Single-Microphone Direction Finding (SMDF) [6]. In this paper we remind the proposed LWA design, and then discuss the application to ADP and SMDF, with simulation and experimental results of the latter.…”