Ultrasound (US) technology has emerged as a powerful modality in both medical imaging and therapy, offering non-invasive, real-time, and high-resolution capabilities. In neuromodulation, particularly for vagus nerve stimulation (VNS), US enables precise anatomical targeting and functional stimulation without surgical implantation of electrodes, reducing procedural risks and improving patient accessibility. Conventional dual-mode systems employ separate ultrasound transducers for imaging and therapy, each mechanically configured during fabrication for a fixed quality factor (Q-factor) through the presence or absence of a backing layer. This approach increases system cost, physical footprint, power consumption, and integration complexity while preventing seamless real-time switching between modes.
This thesis presents a novel electronically configurable Q-factor control architecture for 2D phased-array piezoelectric transducers, implemented in 180 nm CMOS technology, enabling dynamic switching between imaging and therapeutic modes with a single transducer array. The proposed method employs an active damping compensation technique to electronically reduce the Q-factor for imaging mode while preserving the high-Q state for therapy, eliminating the need for mechanical reconfiguration. The architecture integrates a mixed-signal signal chain comprising a fully differential operational transconductance amplifier, an 8-bit SAR ADC, an 8-bit DAC with programmable phase delays, and a high-voltage linear
amplifier, supporting phased-array beamforming for imaging mode of operation. System- and circuitlevel simulations using a PZT-5A air-backed transducer model demonstrate a reduction in the Q factor from 78.3 to 8.08, corresponding to a damping efficiency (FOMQ) of 9.7, with fewer than 1% variation between the process-voltage-temperature corners. These results place the Q-factor achieved in the imaging mode within the optimal range for high-resolution ultrasound imaging, while maintaining high-Q performance for therapy. The proposed architecture offers a compact, cost-effective, and reconfigurable solution for advanced ultrasound platforms in neuromodulation, including real-time image-guided VNS, as well as other biomedical imaging and therapeutic applications.