An RX AFE with Programmable BP Filter and Digitization for Ultrasound Harmonic Imaging

This paper presents a front-end integrated circuit for ultrasound (US) harmonic imaging, interfacing to a one-dimensional capacitive micromachined ultrasonic transducer (CMUT). It contains a complete ultrasound receiving chain, from analog front-end (AFE) to gigabit/s data link. A two-stage self-biased inverter-based transimpedance amplifier (TIA) is proposed in this work to improve tradeoffs between power, noise, and linearity at the first stage. To improve harmonic imaging performance, the design is further equipped with a 4th-order highly programmable bandpass filter, which has a tunable bandwidth from 2MHz to 15MHz. An 8bit 80MS/s SAR ADC digitizes the signal, which is further encoded and serialized into an LVDS data link, enabling a reduction in the number of output cables for future systems with multiple ADCs. The design is realized in a 40nm CMOS technology. Electrical measurements show it consumes 2.9mW for the AFE and 2.1mW for the ADC and digital blocks. Its overall dynamic range varies from 61dB to 69dB, depending on the reception bandwidth. The imaging capability of this design is further demonstrated in a US transmission and reception imaging system. The acoustic measurements prove successful ultrasound harmonic acquisition, where the on-chip bandpass filter can improve the lateral resolution by more than 30%.