Analysis of an underwater elastic leaky wave antenna

Abstract

An acoustic Leaky Wave Antenna (LWA) is an electronically simple device that enables frequency-dependent directional sound radiation or reception by coupling a single acoustic transducer to an analogue dispersive waveguide. While most acoustic LWA have focused on airborne acoustic waves, the successful demonstration of acoustic LWA in the underwater environment has been limited to recent numerical and experimental work by the authors [J. Acoust. Soc. Am., 145(3), 1727 (2019)]. In that work, the LWA was designed through ad hoc iteration of finite element (FE) models which is computationally expensive and therefore does not allow for efficient design space exploration. This work will present the derivation of an approximate analytical lumped parameter model for a one-dimensional underwater acoustic LWA consisting of an elastic bar containing periodically arranged mass-in-cavity inclusions. The analytical model employs long-wavelength expansions of sinusoidally forced continuous elements, resulting in a lumped-element approximate model that can be represented with an equivalent circuit. The lumped parameter approximation is compared with FE results and then used to make improvements on the previously reported LWA design.