Designing a prototype acoustic leaky wave antenna

Abstract

Acoustic direction finding is a useful tool for navigational applications. Current techniques for achieving this rely on the use of many electro-acoustic components, which are expensive to produce and consume a lot of power. Acoustic Leaky Wave Antennas (ALWAs) offer a potential for a low-cost alternative, using much fewer electro-acoustic components and the inherent directionality of the geometrical structure to produce a similar effect. ALWAs possess a directionality which changes with frequency due to their dispersive properties, hence allowing for frequency scanning. Natural material ALWAs can scan angles from broadside (perpendicular to the length of the antenna) to endfire (parallel to the length of the antenna). Metamaterials may be used to extend the range to backfire (180◦ from endfire). This thesis focuses on deriving a model for a rectangular natural material ALWA with either a long slit or a series of periodically spaced circular holes. The theoretical model was tested using Finite Element Method (FEM) simulations in Comsol and experimental measurements of a physical prototype. First, the theoretical model was tested with Comsol simulations. When the model was verified by the simulations, two particular designs with circular holes were chosen for the manufacture of physical prototypes. The directivity of the prototypes was measured using a rotating table and a microphone. Monopole and dipole sources were used to investigate different modes of the ALWA. The results obtained for the ALWA with holes showed good agreement between the theoretical model, the FEM simulation and the experimental measurements. For the slit ALWA, the results were also satisfactory. However, the model may be improved, particularly at lower frequencies.