Abstract
The acoustic analog of the dielectric rod antenna for electromagnetic radiation is investigated both theoretically and experimentally. In acoustics, a cylinder of silicone rubber (whose bulk sound speed is about two-thirds that of water) is analogous to the dielectric rod. An acoustic wave in the direction parallel to the axis of the waveguide is concentrated within the guide by progressive refraction. A hydrophone (whose free-field sensitivity is omnidirectional) is attached near one end of the waveguide and detects this concentrated radiation as a gain in signal for this direction relative to any other direction. Similarly, if the slow waveguide is attached to an acoustic source, it will enhance the source level in the direction of the waveguide. The antenna is mathematically modeled by coupling the surface Helmholtz integral equation appropriate to the region within the silicone waveguide to a similar equation for the water region exterior to the cylinder (which includes the point hydrophone) by requiring continuity of acoustic pressure and normal velocity on the common surface. The coupled integral equations are solved numerically. Predicted beam patterns and directivity gains are in excellent agreement with experiment. Broad-band directivity gains of over 9 dB are both predicted and observed for two test antennas.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call