US Patent 7508737 Ultrasound receive beamformer

In an ultrasound receive beamformer signals from two or more aperture elements are multiplexed at the input of each beamformer channel, stored in different portions of a delay memory, delayed and apodized in a time-multiplexed fashion, demultiplexed at the output of the channel, and summed in different summation units running at an upsampled rate. The partial sums are then time-aligned, summed to produce the total upsampled beam sum, filtered and decimated in an interpolation filter to produce the beamformed signal.