Analog front-end with slow-time feedback for transcranial functional ultrasound
I. Syngelakis (TU Delft - Electrical Engineering, Mathematics and Computer Science)
MAP Pertijs – Mentor (TU Delft - Electronic Instrumentation)
Nuriel N.M. Rozsa – Mentor
Tiago L. Costa – Graduation committee member (TU Delft - Bio-Electronics)
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Abstract
Transcranial Doppler (TCD) ultrasound is a non-invasive technique for assessing cerebral blood flow, offering valuable insights for the diagnosis and monitoring of brain disorders. Despite its importance, its effectiveness is limited by the high dynamic range required at the receiver front-end due to clutter components from skull and tissue reflections. Traditional approaches rely on high-dynamic-range amplifiers and high-resolution ADCs to detect the useful blood flow signal against the clutter signal, leading to high power consumption and data throughput.
This thesis addresses this challenge by incorporating a feedback path from the receiver output directly to the transducer. This approach enables effective clutter suppression, thereby reducing the dynamic range requirements of the receiver chain. To achieve this, the system employs a slow-time integrator at the feedback path, ensuring stable tracking of the clutter component.
Key building blocks, including a boxcar integrator with micro-beamformer functionality, a slow-time delta modulator, a DAC, and a buffer, are thoroughly analyzed. The system is designed and implemented in a TSMC 180\,nm BCD process, realizing an ASIC tailored for an 8-element CMUT array. Simulation results demonstrate the feasibility of reducing the dynamic range requirements by up to 57\,dB with a total power consumption of 1.984\,mW per element, while also providing valuable insights into the trade-offs associated with implementing clutter suppression in a low-power ASIC ultrasound system.