Wideband Ultrasonic Transducer Using Modified Space-Filling Curves

In this paper, a wideband ultrasonic transducer designed by space-filling curves is reported. The transducer is based on the Hilbert space-filling curve, which incorporates some modifications such that a series of identical holes are cut from the piezoelectric membrane. The modification is achieved by relocating one or two segments to form a closed shape. Four ultrasonic transducers (one through four iterations of Hilbert curves) are proposed and compared in terms of resonant frequency, bandwidth, and acoustic intensity response. The fabricated ultrasonic transducers using polyvinylidene fluoride (PVDF) had the resonant frequency around 11.6 MHz with an increasing trend in 3 dB bandwidth as iteration order increases (averaging 11.5% improvement per order increment).