A Directional Dogbone Flextensional Sonar Transducer
Abstract
In order to transmit energy in one direction, sonar flextensional transducers are combined into arrays of elements that are spaced a 1/4 wavelength apart. The directionality (frontto- back pressure ratio) is a modest of 6 dB. A single projector that is 1/3 wavelength in size and capable of developing unidirectional beams with front-to-back ratios greater than 20 dB that is independent of sound speed is described here. The directional Class VII "dogbone" flextensional is a modified version of an elliptical shaped Class IV flextensional having a concave shell rather than a convex one. The piezoelectric ceramic stack is a tri-laminar bar with two active sections separated by an inactive center section. By driving both sections of the stack in-phase, the shell is driven into omnidirectional radiation pattern. Driving each stack section 180 degrees out-phase causes a bending mode in the stack resulting in a dipole radiation pattern. By driving both sections using complex coefficients determined from the omnidirectional and dipole mode patterns, a cardioid directional radiation pattern is developed. Cardioid patterns are developed over an octave frequency band with a front-to-back pressure ratio of more than 50 dB. COMSOL Finite Element Analysis (FEA) code with Acoustics Module is used to predict in-water electroacoustic performance and compared with an experimental data.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 2010
- Accession Number
- ADA584385
Entities
People
- Stephen C. Butler
Organizations
- Naval Undersea Warfare Center