Development of a high frequency (>20 MHz) linear ultrasonic array using fine grain ceramic elements

This study investigates the design tradeoffs involved in the development of a high frequency (35 MHz) 96-element linear array. This array was designed primarily for human eye and skin imaging, and features monolithic elements mechanically diced out of a fine grain high density PZT-5H ceramic. Array elements were spaced with a 50 micron pitch, interconnected via a flexible circuit and matched to the 50 Ohm system electronics via a 75 Ohm transmission line coaxial cable. The final array design was based upon tradeoffs among the level of array encapsulation, suppression of acoustic crosstalk, bandwidth and sensitivity. Several prototype arrays were constructed with promising results. An average center frequency of 34 MHz with a -6 dB bandwidth of at least 45% per element was achieved. The maximum combined electrical and acoustical crosstalk for nearest and next nearest elements was less than -30 dB, and the average -40 dB pulse length was 100 ns.