Design methodology for Class D ultrasound transducer drivers

Ultrasound refers to sound waves with frequencies above the upper limit of human hearing. Due to the high frequency, the energy can be concentrated and used for therapeutic applications, such as ultrasound imaging and therapeutic devices. This thesis focuses on the design of driving circuits for ultrasound transducers. The Class D amplifier loaded with a piezoelectric ultrasound transducer is analyzed, and a design methodology is developed. The resulting design achieves high efficiency and can handle transducer impedance variations by adjusting two capacitances in the matching network. The amplifier topology is simple and low-cost. If this design is implemented in the lab, it will require a variable DC voltage supply, a gate driver, two NMOSs, an L-C filter, and a parallel capacitor. A reference design to drive disc-shaped transducers with a radius of 20 mm, and a thickness of 2.8 mm, made of piezo-composite crystal, is presented to illustrate the design methodology. The resulting amplifier can provide a power of near 50 W at 1034 kHz with 97 % efficiency when driving six different transducer samples. The analysis and design methodology are validated by simulating the amplifier performance in LTSpice and a corner analysis considering matching network component variations

Integrated Circuits for Medical Ultrasound Applications: Imaging and Beyond

Medical ultrasound has become a crucial part of modern society and continues to play a vital role in the diagnosis and treatment of illnesses. Over the past decades, the develop- ment of medical ultrasound has seen extraordinary progress as a result of the tremendous research advances in microelectronics, transducer technology and signal processing algorithms. How- ever, medical ultrasound still faces many challenges including power-efficient driving of transducers, low-noise recording of ultrasound echoes, effective beamforming in a non-linear, high- attenuation medium (human tissues) and reduced overall form factor. This paper provides a comprehensive review of the design of integrated circuits for medical ultrasound applications. The most important and ubiquitous modules in a medical ultrasound system are addressed, i) transducer driving circuit, ii) low- noise amplifier, iii) beamforming circuit and iv) analog-digital converter. Within each ultrasound module, some representative research highlights are described followed by a comparison of the state-of-the-art. This paper concludes with a discussion and recommendations for future research directions