Low power front end electronics for in-probe beamforming in ultrasound imaging

Abstract

A Class AB time gain compensation (TGC) circuit and a switched current analog beam former are designed for an ultrasound low power front-end receiver. The TGC also acts as a voltage to current converter with a peak to peak single-ended input voltage range of 1.8V and a ratio of single sided input current swing to bias current is close to 10. The total power consumption of the fully differential TGC is 100uA/channel. The beam former is a switched current delay line based design with 16 memory cells per channel. The highlight of the beam-former architecture is that the number of storage cells can be easily extended to a desirable value with the current consumption almost being constant. This provides a longer delay line and a higher flexibility for wave shaping during the beam formation. The current consumption of each channel is 422uA and there are total 16 channels for summation in the beam-former. The input signal frequency is 5MHz and the sampling frequency is 25MHz. This assembly achieves 60dB signal to noise ratio after the summation when the single sided signal amplitude is 600mV. The gain variation in the TGC is 20dB and the instantaneous dynamic range is 38dB hence the total dynamic range of the assembly is 58dB. The TGC and the beam-former are designed and simulated in 180nm technology. The total current consumption for the TGC and the beam former along with a bias generation and a digital controller is 8.3mA and occupies an active area of 1.3mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .