Towards Monolithic Mobile Ultrasound Imaging System for Medical and Drone Applications

Ultrasound Imaging System (UIS) has been widely used in medical imaging with its non-invasive, non-destructive monitoring nature; but so far, the UIS has a large form factor, making it difficult to integrate into mobile applications. For drone and robotic vision and navigation, low-power 3-D depth sensing with robust operations against strong/weak light and various weather conditions is crucial. CMOS image sensor (CIS) and light detection and ranging (LiDAR) can provide high-fidelity imaging. However, CIS lacks depth sensing and has difficulty in low-light conditions. LiDAR is expensive and has issues under strong direct interference sources. UIS, on the other hand, is robust in various weather and light conditions and is cost-effective. However, in the air channel, it often suffers from long image reconstruction latency and low framerate.

To address these issues, this talk introduces UIS ASICs for medical and drone applications. The medical UIS ASIC is designed to transmit pulse and receive echo through a 36-channel 2-D piezoelectric Micromachined Ultrasound Transducer (pMUT) array. The 36-channel ASIC integrates a transmitter (TX), a receiver (RX), and an analog-to-digital converter (ADC) within the 250- μm pitch channel while consuming low power and supporting calibration to compensate for the process variation of the pMUT. With its small form factor, Intervascular Ultrasound (IVUS) and Intracardiac Echocardiography (ICE) are viable applications. The ASIC in 0.18- μm 1P6M Standard CMOS is verified with both electrical and acoustic experiments with a 6×6 pMUT array. Also, the ASIC for drone applications generates 28 Vpp pulses in standard CMOS, and the digital back-end (DBE) achieves 9.83M-FocalPoint/s throughput to effectively translate real-time 3-D image streaming at 24 frames/s. With an 8×8 bulk piezo transducer array, the UIS ASIC is installed on an entry-level consumer drone to demonstrate 7-m range detection while the drone is flying. The talk will conclude with interesting future research directions regarding UIS.