Optimum beam steering of linear phased arrays

Influence of phased array element size on beam steering behavior

The influence of several geometric parameters of linear phased arrays was studied. A systematic approach using an automated testing assembly was used to assess the steering performance of the array in a solid medium. In addition to calibrating the transducer with respect to its steering accuracy, this arrangement provided a detailed study of the effects of steering angle, number of elements, inter-element spacing and array aperture on the beam directivity. The experimental results show good agreement quantitatively with the predicted steering characteristics.

Experimental Study of Phased Array Beam Steering Characteristics

A numerical simulation model is presented to investigate the influences of design parameters of linear phased array transducers on beam focusing and steering performance. The characteristic of ultrasonic beam profiles has been simulated on the basis of the Huygen's superposition principle. For the simulation, a linear phased array is considered as the composition of finite number of elements separated by equidistance. Individual elements are considered as two-dimensional point sources. The waves generated from piezoelectric elements are considered as simplified transient ultrasonic waves that are constructed with the cosine function enveloped with a Hanning window. The characteristic of ultrasonic wave propagation into a medium from the phased array transducer is described. The effects of the number, the interelement spacing, steering angle, the focal length, and frequency bandwidth of the piezoelectric elements on beam directivity and ultrasonic pressure field in a linear phased array transducer are systematically discussed.

A parametric study of ultrasonic beam profiles for a linear phased array transducer

Presents simulation results suggesting that 2D arrays constructed by arranging N elements in an exponential spiral, while achieving comparable beam widths, have smaller grating lobes and produce more symmetric point spread functions than random and periodic sparse arrays operating under similar conditions. All simulations were carried out mimicking the function of a commercial ultrasound scanner.

A spiral 2D phased array for 3D imaging

This paper focuses on a newly developed device based on a 2 MHz divided-ring array for nondestructive testing (NDT) application with two rings, 48 elements, and an aperture of 30 mm. Using this array, it is possible to steer an ultrasound beam three-dimensionally in space within a range of * 45 degrees (longitudinal-wave excitation) and * 30-70 degrees (shear-wave excitation). Computations of the directivity pattern, the process of the theoretical optimization, experiments, and a defect reconstruction will be described. One example of a defect reconstruction has been performed representatively, illustrating that the image quality of the first prototype is improved when it is compared to linear array images because of the higher lateral resolution in elevation direction.

H.-P. Schwarz

Papers

Development of a Divided Ring Array for Three-Dimensional Beam Steering in Ultrasonic Nondestructive Testing