Development of a Theoretical Model for Membrane Hydrophone Transfer Characteristics

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Development of a Theoretical Model for Membrane
Hydrophone Transfer Characteristics
Pierre Gélat
3 April 2003
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Background

• Bilaminar hydrophones are extensively used to
  measure and characterise medical ultrasound
  fields
• Developing a hydrophone model would enable users
  to improve the accuracy of their measurements in
  the field of medical ultrasound (phase response,
  deconvolution)
• Type of hydrophone initially modelled 25 ?m film
  thickness 0.5 mm diameter bilaminar membrane
  hydrophones
• Need to generalise model to simulate the response
  of the new generation of Precision Acoustics
  bilaminar membrane hydrophones (15 ?m film
  thickness, 0.4 mm diameter)

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A bilaminar membrane hydrophone
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Diagram of a bilaminar membrane hydrophone
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Hydrophone model assumptions

• 25 ?m pvdf film thickness, 0.5 mm diameter
  bilaminar
• Assume plane wave incidence on hydrophone
• Use transfer matrix formulation to evaluate
  pressure and particle velocities at extremities
  of pvdf layers
• Account for secondary piezoelectric effects
• Model pvdf layers as equivalent voltage sources
  in series with capacitance
• Model leg as distributed series resistance shunt
  capacitance network
• Model coaxial cable as transmission line
• Account for electrical loading on cable (e.g.
  oscilloscope, amplifier, arbitrary load)

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Bilaminar Hydrophone Equivalent Electrical Circuit
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Model input parameters
 
 
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Open-circuit sensitivity
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Predicted phase response
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Prediction of pressure waveform
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Conclusions

• Validation of a model for predicting the transfer
  characteristics of membrane hydrophones
• Can be used to estimate true pressure waveform