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Developing transducer arrays for high frequency medical imaging is complicated because of the extremely small size and spacing of the array elements. For example, a 50 MHz linear phased array requires a center-to-center spacing of only 15 /spl mu/m (one-half wavelength in water) to avoid the formation of grating lobes in the radiation pattern of the array. Fabricating an array with these dimensions is difficult using conventional technology. A split aperture design that permits much larger element spacing (3 to 4 times) while avoiding the formation of grating lobes is described. The 3-D radiation pattern of a 1.9/spl times/1.4 mm, 50-MHz split aperture linear phased array with 33 transmit elements and 33 receive elements has been evaluated theoretically. The azimuthal beam width is 90 /spl mu/m at a distance of 4.0 mm. Grating lobes are suppressed by at least 60 dB at distances >4.0 mm (/spl sim/f/2). The elevation beam width is 220 /spl mu/m at 4.0 mm, and a useful depth of field over the axial range from 4 to 10 mm is obtained.