Comparison of CW beam patterns from segmented annular arrays and squared arrays

Typically, 2D-squared (S) arrays have been proposed to generate ultrasonic volumetric images. This work presents segmented annular (SA) arrays as an a lternative to S arrays for that purpose. In this sense, the beam patterns r adiated by both apertures in continuous wave conditions are compared. The w ell-known spatial impulse response method is used for simulations and a far -field approximation for the array elements is employed. Comparisons are ma de assuming that both radiating apertures have equivalent characteristics. This means that, on the one hand, full radiating apertures of similar size (implying similar radiated energy) are considered and, on the other hand, b oth arrays are formed by equal number of emitting elements which have equiv alent area (meaning similar electronic complexity). Side lobes and grating lobes at the focal plane are analysed in steering conditions for both apert ures. CW beam patterns from S and SA arrays are also compared by varying th e steering angle, the number of array elements. and the aperture size. The benefits of using segmented annular arrays are shown. (C) 2000 Elsevier Sci ence S.A. All rights reserved.