Design of a Test System to Characterize Very High-Frequency Ultrasound Transducer Arrays

A flexible test system is described that has the capability to characterize very high frequency ultrasound transducer arrays up to 128 elements. The system has the capability of testing single element transducers as well as groups of array elements. The R.F. front end electronics consists of pulser circuit, preamp and time gain compensation circuit. The pulser circuit is a high voltage, high speed, switching circuit designed for -60 V pulse amplitude and pulse width as low as 10 ns. The preamp is a low noise, wide bandwidth amplifier and the time gain compensation circuit has a low noise figure and a bandwidth of 75 MHz. Custom, miniaturized PCB’s have been fabricated and tested for the R.F. electronics. The data acquisition system has the capability to synchronously sample 8 channels at 250 MHz , or 16 channels at 125 MHz with 8 bit resolution. Multiplexing and demultiplexing units have been designed and tested for all the 128 channels. The demultiplexers are suitable for frequencies up to more than 100MHz, and the multiplexers have a bandwidth of 700MHz with good off isolation and cross talk. The multiplex/demultiplex architecture gives the test system the capability to perform synthetic aperture processing as well as dynamic apodization. An adapter board interfaces the external components to the PC (digital I/O card). A software control structure for control and synchronization of the system components for 128 elements has been designed and developed. Results are shown for the characterization of individual 50 MHz transducers as well as element responses for a 30 MHz array.