Development of a high frequency (35 MHz) linear ultrasonic array using 2-2 composite elements [biomedical applications]

This paper discusses the development of a 35 MHz composite ultrasonic array. This array was designed primarily for ocular imaging applications, and features 2-2 composite elements mechanically diced out of a fine grain high density Navy VI ceramic. Array elements were spaced at a 50 μm pitch, interconnected via a custom flexible circuit and matched to the 50 Ω system electronics via a 78 Ω transmission line coaxial cable. Elevation, or off axis, focusing was achieved using a cylindrical epoxy lens. A 64-element array was fabricated and tested, yielding promising results. An average center frequency of 34 MHz was achieved with an average -6 dB bandwidth of 57.8 % and average -20 dB pulse length of 102 ns. The maximum combined electrical and acoustical crosstalk between adjacent or next adjacent elements was less than -24 dB. The 35 MHz array developed is capable of resolving structures in the human body that are smaller than 0.1 mm.