Front-end Circuit Design And Research In The AD9273-based All Digital B-mode Medical Imaging System

As a safe, convenient, non-destructive and inexpensive medical technology, medical ultrasound imaging has been playing an important role in clinical medical applications. Digital ultrasonic technology involve exact launch time delay control, digital echo signal processing, digital beam forming and digital scan conversion and other key technologies. The ultrasound imaging is developing towards the digital technology in which the analog circuits will be replaced by digital circuits of ultrasound imaging system. The front-end system is an important part in the digital ultrasound imaging system. The ultrasonic transmitting and receiving part has a direct impact on the performance of B mode ultrasound imaging quality. Therefore, to design front-end circuit with high performance is of theoretical value and practical significance for improving ultrasound imaging quality.This paper is focused on the design of AD9273-based front-end circuit in the B-mode medical imaging system. Front-end circuit consists of ultrasonic excitation circuit, sensor gating circuit, isolation protection circuit and ultrasonic echo signal processing channel. Ultrasonic high-voltage pulse emission circuit realizes the function of array element excitation inside the ultrasound probe. Array element switching circuit stimulates the array elements according to different sequential requirements. Isolation circuit prevents the high voltage signal from entering and burning the back-end echo signal processing circuit. The echo signal processing part includes low-noise amplifier, variable gain amplifier, antialiasing filter and high-speed analog-digital conversion. The received echo signals are transformed into digital signals which will be used for post-processing digital beamforming. The testing and verification of each module in the front-end circuits are conducted. The testing results show that the design of AD9273-based front-end ultrasound systems can achieve transmission and receiving ultrasonic signals, signal amplification, filtering and ADC functions.The AD9273 based front-end circuit is designed by means of ADI chips and it has good compatibility and stability. The research work in this paper will lay a good foundation for the continuous research on the application of front-end circuits to digital ultrasound imaging system.