Medical diagnostic ultrasound imaging is performed with a multi-dimensional transducer array and an imaging system for planar scanning. The elements of the array may be distributed on a periodic grid with aperiodic shifts in position. When a one-dimensional array is formed on the array, the aperiodic shifts better distribute acoustic energies, reducing peaks in side lobes. Using a layered structure of switches underneath the acoustic elements, side lobes may be further reduced. The switches are used for interconnecting elements to form macro elements of the one-dimensional aperture on the multi-dimensional array. The switches are distributed on a grid corresponding to the desired imaging frequency. The acoustic elements are distributed with a finer pitch. The finer pitch allows formation of the macro elements for the one-dimensional aperture where the edges of the macro elements have fewer or no periodic patterns.