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We describe the development of an integrated, miniaturized ultrasound system designed for use with low-voltage piezoelectric transducer arrays. The technology targets low-frequency NDT and medium- to high-frequency sonar applications, at 1.2 MHz frequency. We have constructed a flexible, reconfigurable, low cost building block capable of 3-D beam forming. The tessellation of multiple building blocks permits formation of scalable 2-D macro-arrays of increased size and varying shape. This differs from conventional ultrasound solutions by integrating the entire system in a single module. No long RF cables are required to link the array elements to the electronics. The close coupling of the array and electronics assists in achieving adequate receive signal amplitudes with differential transmission voltages as low as +/- 3.3 V, although the system can be used at higher voltages. The system has been characterized by identifying flat-bottomed holes as small as 1 mm in diameter located at depths up to 190 mm in aluminum, and holes as small as 3 mm in diameter at a depth of 160 mm in cast iron. The results confirm the ability of the highly integrated system to obtain reflections from the targets despite the +/- 3.3 V excitation voltage by exploiting coding in low-voltage ultrasound.

IntroductionUltrasound systems traditionally increase sample area or resolution by increasing the number of elements (1) , with a corresponding increase in the physical and electrical complexity of such systems. By adopting a different approach of using generic building blocks of 2D elements, coupled to associated electronics, a full 3D volume can be sampled from a single point allowing fast and accurate image collection with greater sample area or enhanced resolution obtainable by increasing the number of modules in use.Due to dimensional constraints it is increasingly common for portable hand-held array-based NDT systems to have electronics in close proximity to the transducer array. Impedance matching between transducers and electronics can be hard to achieve and retain in a practical system. Cumulative impedance mismatches over time between the electronics and the individual transducers can greatly impair the signal-to-noise ratio. One possible solution lies with the avoidance of cables. Previous solutions aimed at integrating the transducer and associated electronics, usually on the same silicon substrate, have resulted in very closely coupled designs which can limit the flexibility should it be desirable to modify the array configuration to suit a particular application. This paper presents, as an alternative, the concept of a modular ultrasonic imaging system utilising generic building blocks of 2D array element configurations to construct low-cost ultrasonic array systems of any size and shape, resulting in a fully scalable solution without requiring redesign. This system can be seen as a mosaic consisting of multiple tiles which can be tessellated to form reconfigurable arrays of any size and shape.Each module, or tile, integrates a 16-element piezocomposite transducer array in a 4 × 4 matrix together with the analogue electronics necessary for full transmit-receive capability on all 16 channels, thus resolving the scaling difficulties that exist due to corresponding increases in quantity and complexity of transmission and reception electronics (1,2) . Unlike traditional ultrasonic systems, the drive electronics are situated adjacent to the sensor head to eliminate the use of long cables and hence minimise parasitic capacitances that degrade the strength of the received signal (1) which is of prime importance to enable low-voltage excitation.The ability to form ultrasound systems in this way, from generic building blocks which are physically identical for manufacturing purposes yet functionally unique via programming to suit the application, has the potential to transform ultrasonic NDT with arrays as it would permit the functionality of off-the-shelf hardware to be tailored to suit any given target application (3) in a field where equipment has traditionally been highly application-specific, a point increasingly considered in research in ultrasonics (4) . The next section provides more information on the basic concept and its potential applications. This is followed by more detailed technical informati...

This paper documents the development of a scalable 2D array system, or Mosaic that can be targeted at a wide range of NDT applications by way of a reconfigurable tile that can be tessellated to form arrays of any size and shape. Close coupling permits utilization of excitation voltages as low as +/-3.3V with insertion loss of 48dB on reflection from an aluminum back wall at 73mm achieved using 2D arrays without decoding.

Abstract-An investigation into the development of an ultrasound imaging system capable of customization for multiple applications via the tessellation of in-system programmable scalable modules, or tiles, is presented here. Each tile contains an individual ultrasonic array, operating at +/-3.3V, which can be assembled into a larger 'mosaic' of multiple tiles to create arrays of any size or shape. The ability to form an imaging system from generic building blocks which are physically identical for manufacturing purposes yet functionally unique via programming to suit the application has many potential benefits in the field of ultrasonics. The system is primarily targeted at underwater sonar and non-destructive testing, as defined by the current excitation frequency, but the concept is equally applicable to applications in biomedical ultrasound.