Use of a Conical Axicon as a Surface Acoustic Wave Focusing Device

1987-1
Atalar, Abdullah
Koymen, Hayrettin
Ultrasonic axicons generate waves which focus on a line. They are used in various imaging applications as hulk wave focusing devices with a very long depth of focus. A new type of conical axicon is introduced. It consists of a concave parabolic surface immersed in a liquid medium and insonified obliquely by wavefronts generated by a plane transducer. The parabolic cylinder can be approximated by a portion of a circular cylinder without losing significantly in the focusing performance of the axicon. It is also shown that conical axicons can be used to excite surface waves provided that the cone angle of the axicon coincides with the Rayleigh critical angle of the liquid-solid interface. The generated surface waves focus into a diffraction-limited spot. This new surface wave focusing scheme is easy to use and has a conversion efficiency and sensitivity far better than other existing techniques.
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control

Suggestions

Finite element modeling and experimental characterization of crosstalk in 1-D CMUT arrays
Bayram, Barış; Yaralioglu, Coksen G.; Oralkan, Omer; Ergun, Arif Sanli; Lin, Der-Song; Wong, Serena H.; Khuri-Yakub, Butrus T. (Institute of Electrical and Electronics Engineers (IEEE), 2007-02-01)
Crosstalk is the coupling of energy between the elements of an ultrasonic transducer array. This coupling degrades the performance of transducers in applications such as medical imaging and therapeutics. In this paper, we present an experimental demonstration of guided interface, waves in capacitive micromachined ultrasonic transducers (CMUTs). We compare the experimental results to finite element calculations using a commercial package (LS-DYNA) for a 1-D CMUT array operating in the conventional and collap...
Estimation of Articulatory Trajectories Based on Gaussian Mixture Model (GMM) With Audio-Visual Information Fusion and Dynamic Kalman Smoothing
ÖZBEK, İbrahim Yücel; Hasegawa-Johnson, Mark; Demirekler, Mübeccel (Institute of Electrical and Electronics Engineers (IEEE), 2011-07-01)
This paper presents a detailed framework for Gaussian mixture model (GMM)-based articulatory inversion equipped with special postprocessing smoothers, and with the capability to perform audio-visual information fusion. The effects of different acoustic features on the GMM inversion performance are investigated and it is shown that the integration of various types of acoustic (and visual) features improves the performance of the articulatory inversion process. Dynamic Kalman smoothers are proposed to adapt t...
Utilization of anisotropic metamaterial layers in waveguide miniaturization and transitions
Ozgun, Ozlem; Kuzuoğlu, Mustafa (Institute of Electrical and Electronics Engineers (IEEE), 2007-11-01)
We introduce a new approach which enables a waveguide to support propagation of electromagnetic waves below the cutoff frequency, as well as which avoids undesirable reflections in a waveguide. These are achieved through the usage of an anisotropic metamaterial layer by employing the concept of coordinate transformation. The proposed method can be utilized for the fabrication of miniaturized waveguides, and for the elimination of discontinuities in abrupt waveguide transitions. We demonstrate some numerical...
Prediction of ducted diaphragm noise using a stochastic approach with adapted temporal filters
Karban, Ugur; Schram, Christophe; Sovardi, Carlo; Polifke, Wolfgang (SAGE Publications, 2019-01-01)
The noise production by ducted single- and double-diaphragm configurations is simulated using a stochastic noise generation and radiation numerical method. The importance of modeling correctly the anisotropy and temporal de-correlation is discussed, based on numerical results obtained by large eddy simulation. A new temporal filter is proposed, designed to provide the targeted spectral decay of energy in an Eulerian reference frame. An anisotropy correction is implemented using a non-linear model. The acous...
Dynamic Speech Spectrum Representation and Tracking Variable Number of Vocal Tract Resonance Frequencies With Time-Varying Dirichlet Process Mixture Models
Özkan, Emre; Demirekler, Muebeccel (Institute of Electrical and Electronics Engineers (IEEE), 2009-11-01)
In this paper, we propose a new approach for dynamic speech spectrum representation and tracking vocal tract resonance (VTR) frequencies. The method involves representing the spectral density of the speech signals as a mixture of Gaussians with unknown number of components for which time-varying Dirichlet process mixture model (DPM) is utilized. In the resulting representation, the number of formants is allowed to vary in time. The paper first presents an analysis on the continuity of the formants in the sp...
Citation Formats
A. Atalar and H. Koymen, “Use of a Conical Axicon as a Surface Acoustic Wave Focusing Device,” IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, pp. 53–63, 1987, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/52075.