Evaluation of an acoustic metamaterial leaky-wave antenna

Abstract

An acoustic projector array, which can be steered between ± 90 degrees backfire to endfire directions based solely on input frequency, is presented using a combination of transmission line (TL) analysis and negative index metamaterial ideas. An acoustic version of a leaky wave antenna, this TL structure is composed of acoustically loaded membranes (acoustic masses) and open channels (acoustic shunts). This type of TL structure had been shown previously to have broadband negative index behavior below a cutoff frequency, and positive index behavior above the cutoff frequency. By carefully designing the geometry of the acoustic elements, continuous scanning with no acoustic bandgap was achieved. The fast-wave radiation band of the antenna was determined using a lumped acoustic parameter method. Angle of radiation of the acoustic waves out of the acoustic shunts was continually scanned backfire-to-endfire, including broadside. Applications of this antenna structure include both source and sensing technologies. Finite element analyses and acoustic circuit analysis were used to predict the angle of radiation of the antenna which agreed with experimentally obtained results. © 2013 Acoustical Society of America.