A modular FPGA-based ultrasonic array system for applications including non-destructive testing

Abstract

This paper reports work aimed at the development of an ultrasonic imaging system comprising modular, reprogrammable building blocks, or 'tiles', which can be customised for multiple applications, including and within non-destructive testing (NDT), by the user. The key component is an autonomous module containing the ultrasonic array and all the electronics necessary to operate it. This contrasts with most previous research on system integration which has focused only on the transducer and front-end electronics. In the present work, a 4 x 4 element 2D piezoelectric array with a 16 mm x 16 mm aperture has been produced, with the entire transmission and reception electronics within the same footprint. The proximity of the transducer array and electronics removes the need for cabling, reducing signal degradation due to cross talk and interference. In addition, it avoids the problem of electrical impedance matching of cable between the array elements and the electronics. Pulse-echo insertion loss of 48 dB has been measured from back-wall reflections in 73 mm-thick aluminium without decoding, and results with decoded signals show adequate signal-to-noise ratio (SNR) with ±3.3 V excitation at an operating frequency of 1.2 MHz, within the range required for deep penetration in nuclear power plant. Crucially, the ability to construct 2D arrays of any size and shape from generic building blocks represents a departure from almost all previous work in ultrasound, which has traditionally been highly application specific. This may allow ultrasonic NDT to be used in applications for which the investment in customised devices could not previously be justified.