Ultrasound based sensing modality is one of the oldest in medical and industrial applications. Advancements in micromachining techniques opened up possibilities to develop micromachined ultrasonic transducers (MUTs). Of these, capacitive micromachined ultrasonic transducer (CMUT) technology has proven to be a promising alternative to conventional bulk piezoelectric based ultrasonic transducers. This enabled the design and development of miniaturized CMUT based sensor solutions for a wide range of applications. The medical imaging has benefited a lot from the advancements in CMUT fabrication technology. Advances in high voltage (HV) integrated circuit design processes for high voltage and high power applications opened up the opportunity to design highly compact application specific integrated circuits (ASIC) for such transducers. The CMOS compatibility of CMUTs makes it a very attractive option for a monolithic integrated CMUT sensor system. In this thesis, the design of integrated circuits to interface a CMUT array is addressed. Circuit architectures are investigated and implemented to enable a highly integrated CMUT-ASIC system. A novel CMUT driving architecture is presented which eliminates the need to use an external bias tee circuit to bias the CMUT to HV levels. The structure also helps to avoid the use of HV isolation switch in the receive path of the transceiver channel. This reduces the die area and helps to improve the signal to noise ratio (SNR). Design and implementation of an 8 channel transceiver ASIC in 0.18 μm HV silicon on insulator (SOI) technology is presented. Design of key circuit blocks in the transmit path including HV pulsers, level-shifters, HV linear regulator and other auxillary circuits are provided and the performance verification through silicon measurements are also presented. In the receive path, a resistive feedback transimpedance amplifier (TIA) is used for converting the time varying input current into an output voltage. Four adjustable gain settings are possible for the designed TIA. Measurement results are provided which validates the analysis and design presented. A pulse-echo measurement result demonstrates the capability of the complete system to be operated as proposed. A transmit beamforming circuit for phased array actuation of CMUT arrays is presented in the final part of the thesis. An architecture combining an analog wide-range delay locked loop (DLL) and digital circuits is implemented. Such a very low-power area efficient approach demonstrates the possibilities of circuit integration on front-end ASICs for CMUT based imaging devices. Extensive simulation results presents the feasibility of the proposed solution to perform a high resolution beam focusing and steering using only a single low frequency clock source. The digital circuit blocks provide further flexibility to the ASIC by adding of frequency division and pulse count functionality.    «

Ultrasound based sensing modality is one of the oldest in medical and industrial applications. Advancements in micromachining techniques opened up possibilities to develop micromachined ultrasonic transducers (MUTs). Of these, capacitive micromachined ultrasonic transducer (CMUT) technology has proven to be a promising alternative to conventional bulk piezoelectric based ultrasonic transducers. This enabled the design and development of miniaturized CMUT based sensor solutions for a wide range o...    »