Supply-Doubled Pulse-Shaping High Voltage Pulser for CMUT Arrays

A low-complexity and high-frequency ASIC transceiver for an ultrasound imaging system

This article presents a high-frequency application-specific integrated circuit (ASIC) transceiver for an ultrasound imaging system designed with a focus on low complexity. To simplify the design, it employs a conventional Class-D power amplifier structure for the transmitter (TX) and a resistive feedback transimpedance amplifier (TIA), which consists of a common-source amplifier followed by a source follower for the receiver (RX). Through careful optimization, the RX achieves a measured transimpedance gain of 90 dBΩ and an input-referred noise of 5.6 pA/√Hz at 30 MHz while maintaining a wide bandwidth of up to 30 MHz for both the TX and RX. The power consumption of the TX and RX is measured to be 7.767 mW and 2.5 mW, respectively. Further acoustic performance, assessed using an annular capacitive micromachined ultrasonic transducer (CMUT), showed a 1.78 kPa peak pressure from a 20 V pulser and confirmed the full bandwidth compatibility of the CMUT's bandwidth. The ASIC transceiver has been fabricated using a 0.18 μm HV bipolar-CMOS-DMOS (BCD) process.

Circuits on miniaturized ultrasound imaging system-on-a-chip: a review

Trends of medical system move from a traditional in-person visit to virtual healthcare increases demands on point-of-care devices. Because ultrasound (US) is non-invasive, the demands highlight US imaging among other imaging modalities. Thanks to the development of US transducer technology, miniaturized US with application-specific integrated circuits (ASIC) have been researched. For example, applications that require small aperture sizes such as intravascular US (IVUS) and intra-cardiac echocardiography (ICE) require integration of system-on-a-chip (SoC) on the transducer. This paper reviews circuit techniques on the transmitter (TX) and receiver (RX) of the US imaging system. As TX circuits, pulser, T/RX switch, TX beamformer, and power management circuits are discussed. State-of-the-art transducer modeling, pre-amplifier, time-gain compensation, RX beamformer, quadrature sampler, and output driver are introduced as RX circuits.

Integrated Circuits for Medical Ultrasound Applications: Imaging and Beyond

Medical ultrasound has become a crucial part of modern society and continues to play a vital role in the diagnosis and treatment of illnesses. Over the past decades, the development of medical ultrasound has seen extraordinary progress as a result of the tremendous research advances in microelectronics, transducer technology and signal processing algorithms. However, medical ultrasound still faces many challenges including power-efficient driving of transducers, low-noise recording of ultrasound echoes, effective beamforming in a non-linear, high-attenuation medium (human tissues) and reduced overall form factor. This paper provides a comprehensive review of the design of integrated circuits for medical ultrasound applications. The most important and ubiquitous modules in a medical ultrasound system are addressed, i) transducer driving circuit, ii) low-noise amplifier, iii) beamforming circuit and iv) analog-digital converter. Within each ultrasound module, some representative research highlights are described followed by a comparison of the state-of-the-art. This paper concludes with a discussion and recommendations for future research directions.

Supply-Inverted Bipolar Pulser and Tx/Rx Switch for CMUTs Above the Process Limit for High Pressure Pulse Generation

A combined supply-inverted bipolar pulser and a Tx/Rx switch is proposed to drive capacitive micromachined ultrasonic transducers (CMUTs). The supply-inverted bipolar pulser adopts a bootstrap circuit combined with stacked transistors, which guarantees high voltage (HV) operation above the process limit without lowering device reliability. This circuit generates an output signal with a peak-to-peak voltage that is almost twice the supply level. It generates a bipolar pulse with only positive supply voltages. The Tx/Rx switch adopts a diode-bridge structure with the protection scheme dedicated to this proposed pulser. A proof- of-concept ASIC prototype has been implemented in 0.18-μm HV CMOS/DMOS technology with 60 V devices. Measurement results show that the proposed pulser can safely generate a bipolar pulse of -34.6 to 45 V, from a single 45 V supply voltage. The Tx/Rx switch blocks the HV bipolar pulse, resulting in less than 1.6 V at the input of the receiver. Acoustic measurements are performed connecting the pulser to CMUTs with 2 pF capacitance and 8 MHz center frequency. The variation of acoustic output pressures for different pulse shapes were simulated with the large signal CMUT model and compared with the experimental results for transmit pressure optimization. A potential implementation of the methods using MEMS fabrication methods is also described.

A Reduced-Wire ICE Catheter ASIC With Tx Beamforming and Rx Time-Division Multiplexing

This paper presents a single chip reduced-wire active catheter application-specific integrated circuit (ASIC), equipped with programmable transmit (Tx) beamforming and receive (Rx) time-division multiplexing (TDM). The proposed front-end ASIC is designed for driving a 64-channel one-dimensional transducer array in intracardiac echocardiography (ICE) ultrasound catheters. The ASIC is implemented in 60 V 0.18-μm HV-BCD technology, integrating Tx beamformers with high voltage pulsers and Rx front end in the same chip, which occupies 2.6 × 11 mm2 that can fit in the catheter size of 9 F (<3 mm). The proposed system reduces the number of wires from >64 to only 22 by integrating Tx beamformer that is programmable using a single low-voltage differential signaling data line. In Rx mode, the system uses 8:1 TDM with direct digital demultiplexing providing raw channel data that enables dynamic Rx beamforming using individual array elements. This system has been successfully used for B-mode imaging on standard ultrasound phantom with 401 mW of average power consumption. The ASIC has a compact element pitch-matched layout, which is also compatible with capacitive micromachined ultrasound transducer on CMOS application. This system addresses cable number and dimensional restrictions in catheters to enable ICE imaging under magnetic resonance imaging by reducing radio frequency induced heating.