HP Labs Technical Reports

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High Frequency Membrane Hydrophone

Lum, Paul; Greenstein, Michael; Grossman, Charlie; Szabo, Tom



Abstract: A membrane hydrophone with a 37 um diameter spot poled electrode has been fabricated on a 4 um thick film of the piezoelectric copolymer, Polyvinylidene fluoride trifluoroethylene (PVDF-TrFE), and initially characterized. The hydrophone has an effective spot size of less than 100 um, an on-membrane +7 dB gain buffer amplifier, and a -3 dB bandwidth of 150 MHz. The acoustic properties of the hydrophone were investigated with a transducer equivalent circuit model, the electric fringe fields due to poling were characterized with a finite difference electrostatic field model, and the effective spot diameters 2a(sub 3) and 2a(sub 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 high frequency transducers such as intravascular catheter transducers operating in the 10 - 40 MHz range.

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