HIGH-FREQUENCY MEMBRANE HYDROPHONE

A membrane hydrophone with a 37-mu m diameter spot poled electrode has been fabricated on a 4-mu m-thick film of the piezoelectric copolymer , polyvinylidene fluoride triflnoroethylene (PVDF-TrFE), and initially characterized. The hydrophone has an effective spot size of less than 100 mu m, an on-membrane +7-dB gain buffer amplifier, and a -3-dB ban dwidth of 150 MHz. The acoustic properties of the hydrophone were inve stigated with a transducer equivalent circuit model, the electric frin ge fields due to poling were characterized with a finite difference el ectrostatic field model, and the effective spot diameters 2a(3) and 2a (6) were estimated, Measurements on the bandwidth, effective spot size , and sensitivity are presented, This hydrophone appears suitable for the characterization of both the frequency and spatial parameters of h igh-frequency transducers such as intravascular ultrasound (IVUS) cath eter transducers operating in the 10-40 MHz range.