beamformer 2 is coupled to the left end of the transducer array and focused beams of ultrasound may be transmitted and received to acquire data for the corresponding edge of the image as the point of origin of successive ultrasound beams steps along transducer array 24 to the right it becomes advantageous to shift the active aperture so that the origin of the ultrasound beam is centered within it to shift the aperture from the extreme left end of the array by one element toward the right the multiplexer switch coupled to element 0 is opened and the switch coupled to element 128 is closed this shifts beamformer channel 0 from the left end to the right side of the active aperture while leaving all other channels and elements connected as before the time delays and other beamforming parameters are changed by the software to correspond to the new multiplexer state and one or more additional image vectors are acquired then the aperture is stepped further to the right by opening the switch coupled to element 1 and closing the switch coupled to element 129 leaving multiplexer 36 in the state shown in fig2 in this manner the active aperture can be stepped sequentially from one end of the tranducer array 24 to the other alternatively the same multiplexer hardware may be used to scan the active aperture.