Curved annular array transducers made from composite piezoelectric materials

Spherically curved annular-array transducers have been developed using a composite piezoelectric material. The composite material allows the construction of sensitive, high-resolution arrays with elements defined by the electrode pattern alone. The array elements exhibit uniform properties and clean thickness-mode oscillations uncoupled to spurious lateral resonances. A prototype 3-MHz array exhibits a minimum insertion loss of 8 dB with a 6-dB fractional bandwidth of 57%. The -20-dB and -40-dB ringdown times in this array correspond to 3.3 and 6.2 periods, respectively.