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Doctoral Defense

Design Methodologies to manage Switching Noise with Applications to Biomedical Acoustic Systems

Zhihua Gan

July 25, 2017
Bioengineering Building room 202
Advisor: Emre Salman

Noise and power efficiency are two critical issues in modern integrated circuits design that highly impact the system performance. Due to the high density of circuits, different circuit modules are mounted on the same die closely. Specifically, in a mixed-signal environment, switching noise due to substrate coupling propagates from digital circuits to analog parts. In the meantime, analog circuits also suffer from the intrinsic device noise such as thermal, flicker, shot noise. Thus, a challenging issue during the design process of analog circuits is the evaluation of the dominant noise source. An analysis flow is proposed to show the fair comparison between switching noise and device noise in two commonly used amplifiers.

Power supply noise is known as a primary source of switching noise. Voltage regulators are typically used to ensure stable power supply voltage with tolerable noise. A buck voltage regulator with 87% power efficiency is introduced in this thesis. Typical buck converters with on-chip inductors have high switching frequency to reduce the stringent inductor size. High quality factor inductors are built by fully utilizing the flexibility of the package space, resulting in a comparatively low switching frequency of the buck converter.

Several works related to ultrasound transducer design and front-end circuit design are introduced. Ultrasound thus can be applied to human beings in a daily base for bone density treatment. A 5 by 5 low intensity pulse ultrasound system is developed to reduce bone density loss. Ultrasound signals are excited in a certain time sequence to focus on dynamic targets. A 27 by 27 phased array transducer is designed, simulated and verified by FIELD II for sub-block structure effect as part of flexible ultrasound system. 

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