Current‐mode ultrasound beamformer with multiple‐input–sequential‐output memory structure

Abstract

A current-mode ultrasound beamformer (BF) is proposed. Each channel of BF converts the echo voltage signal into current and performs uniform sampling. The sampled current of each channel is injected into one of the memory capacitors depending on a delay profile at time instance when the echo signal is sampled. Since multiple currents can be simultaneously added in parallel, multiple signal currents in parallel can be injected into one shared capacitor. By using this inherent characteristic of current-mode operation, BF of this work has a 1D memory structure unlike a 2D memory structure of other prior BFs. The proposed memory structure allows simultaneous access from multiple channels and sequential read-out operation. The proposed architecture of BF was verified by simulating an eight-channel BF using a high-voltage 0.18 μm CMOS process. Symmetric and linear delay profiles are applied to the designed BF and an output waveform of BF shows a good agreement with the derived channel gain equation. The BF consumes 220 μW/channel during receiving mode.