In medical ultrasound imaging, beam control methods such as dynamic focusing, and dynamic aperture and weighting give a need for more flexible control over the receive beam. In addition the desire to increase acquired framerate makes it a requirement to be able to receive several beams in parallel for each transmitted beam. Digital beamforming implemented with custom VLSI chips will give these capabilities. This paper therefore discusses various concepts for digital beamforming and also gives a discussion of the effect of time delay quantization in beamforming under conditions of steering and focusing.