A tri-modal directional transducer

Abstract

Acoustic transducers made from piezoelectric ceramic cylinders usually exploit the breathing or omnidirectional (omni) mode of vibration. However, with suitable voltage distribution, higher order extensional modes of the cylinder can be excited which produce directional radiation patterns. These modal radiation patterns can then be combined to synthesize desired beam patterns which may be steered by incrementing the excitation. This paper describes a model for the combined acoustic response of the extensional modes of vibration of a piezoelectric ceramic cylinder, a method of synthesizing a desired radiation pattern, and an experimental implementation of a directional transducer that uses these techniques. This tri-modal transducer is broadband and directional with a frequency independent beam pattern yet simple, small, and lightweight.

Directional magnetoelectric effect in multi-electrode Pb(Zr,Ti)O3/Ni cylindrical layered composite

“…, where f 0 is the resonance frequency of the fundamental extensional mode with the mode number n = 0 [24,25]. Based on this, the first peak at 42 kHz corresponds to the fundamental extensional mode, while the second peak in the vertical mode corresponds to the third extensional mode with n = 2.…”

“…The strain transferred to the piezoelectric phase of units 1 and 3 differs from that of units 2 and 4 as a result of different magnetization in the Ni layers. Similar to the electric field voltage distribution exciting the third extensional mode of the piezoelectric ceramic ring [24,25], the third extensional mode of the PZT ring can be activated. Since the ring vibrates in the third extensional mode, there are four longitudinal nodal lines with zero displacement.…”

Forming First-and Second-Order Cardioids with Multimode Hydrophones

“…Partially Assembled Unit (7) Bx X c(e, +e8)+(e4 +e5) -(e2 +e3) -(e6 +e7)=>cos20 -sin20 The hydrophone shown in Fig. 6 was tested at the anechoic tank facility located at the Pennsylvania State UniversityApplied Research Laboratory in which the FFVS and directivity patterns were measured using the standard sourcereceiver configuration typical of transducer calibration.…”

“…Other researchers such as Cray [5] and Silvia [6] have used the theory to optimize sonar signal processing algorithms while others such as Butler [7] and McConnell [8][9][10] have developed highly directional transducers for transmit and receive applications, respectively. This paper summarizes the work done by the authors to develop highly directional receivers using cylindrical multimode hydrophones.…”

The modal projector

“…Although these approaches can provide a high directivity index 5 (DI) and very narrow beam from a small source or array, the reproduction and efficiency of the device can suffer from large phase variations over the array or the higher order modes of the spherical radiator. Butler et al 6 showed that a practical cylindrical transducer with modest directivity can be obtained if the number of modes is limited to the first three modes. We note that the use of the first two modes 7 in a sonar system goes back to at least 1966.…”