Design of a front-end ASIC for a fully integrated ultrasound PMUT array in CMOS

Student thesis: Doctoral thesis

Abstract

Nowadays, the advances in miniaturized MEMS ultrasonic transducers require major efforts in the design of the interface electronic circuits in order to take advantage of their lower power consumption, small size, and low fabrication cost. In this context, this Ph.D. thesis has focused on developing of an Analog Front-end Application-Specific Integrated Circuit (ASIC) for a fully integrated ultrasound phased array based on piezoelectric micromachined ultrasonic transducers (pMUT). The main goal is to achieve a compact system-on-chip ultrasound sensor with low power consumption and improved performance in terms of signal-to-noise ratio capable of being used in ultrasound imaging and ranging applications. In particular, this thesis was aimed at the design and implementation of the electronics in charge of the generation of the PMUT driving signals, as well as the amplification of the PMUT signals generated, when the PMUT is working as a sensor. In this context, to optimize area, power consumption, and transmission efficiency, it has been proposed an HV Pulser based on level shifters and inverters, which is able to rise monophasic pulses from 3.3 V to 32 V. On the other hand, the reception analysis was performed to achieve a tradeoff between noise performance, gain, and area needs. The proposed RX amplifiers include two LNA topologies (a voltage amplifier and a trans-impedance amplifier based on capacitive feedback), and a variable gain amplifier to implement the time-gain compensation function. The PMUTs-on-CMOS ultrasound systems were validated, first, through a single pixel element capable to achieve higher signal-to-noise ratio levels in comparison with the non-integrated system using the same fabrication process. Based on the excellent results achieved, a phased array (PMUTs-on-CMOS) was discussed and validated as a compact ultrasound system for imaging applications. Finally, the last chapter was dedicated to presenting a new strategy to estimate very short relative distances with high accuracy based on the use of multi-frequency pulsed waves which opens the way to a future application of this system in CMOS electronic circuitry.
Date of Award28 Nov 2022
Original languageEnglish
Awarding Institution
  • Universitat Autònoma de Barcelona (UAB)
SupervisorMaria Aranzazu Uranga del Monte (Director)

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