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Thesis
Development of programmable front-end electronics for use with ultrasound hydrophone
Master of Science (M.S.), Drexel University
Aug 2003
DOI:
https://doi.org/10.17918/etd-223
Abstract
Piezoelectric sensors are widely used in many bioengineering applications. However, the sensors exhibit high, on the order of MegaOhms, output impedance and, therefore, the signal generated at the output terminals of a sensor needs to be electronically conditioned prior to further use. Specifically, it is necessary to incorporate a high quality preamplifier between the sensor and analyzing equipment. Such preamplifiers are not commercially available. This work describes development of a programmable preamplifier tailored for use with miniature piezoelectric polymer hydrophones for characterization of acoustic output of ultrasound scanners. Such scanners are used in almost all medical fields and are becoming the preferred imaging modality in a variety of clinical situations. The preamplifier features 50 output impedance to eliminate transmission line phenomena, and high input resistance (1M) which minimizes loading of the hydrophone. The frequency response of the preamplifier was optimized to comply with the Food and Drug Administration (FDA) requirements; the circuit operates between 100 kHz and 40 MHz. To optimize the performance in terms of input impedance, frequency response and dynamic range, the preamplifier was implemented in two stages using application specific operational amplifiers. Visual Basic program was employed to automatically execute On/Off function of the buffer circuit. The implemented circuit topology allows fully automatic determination of key acoustic output parameters of diagnostic ultrasound scanners, which, in turn, determine the safety indicators such as Mechanical Index (MI) and Thermal Index (TI). To verify the performance of the programmable preamplifier, several ultrasound hydrophones were measured and calibrated with and without preamplifier. The measurement results are presented in terms of end-of-cable voltage sensitivity as a function of frequency. Also, the impedance of the preamplifier and programmable buffer circuit were determined as a function of frequency. In addition, the circuit's scattering parameter S21 that is its transfer function versus frequency was measured. Future work will focus on extension of the preamplifier's bandwidth up to 100 MHz.
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Details
- Title
- Development of programmable front-end electronics for use with ultrasound hydrophone
- Creators
- Sumet Umchid - DU
- Contributors
- Peter Andreas Lewin (Advisor) - Drexel University (1970-)Philip E. Bloomfield (Advisor) - Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Master of Science (M.S.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Resource Type
- Thesis
- Language
- English
- Academic Unit
- School of Biomedical Engineering, Science, and Health Systems (1997-2026); Drexel University
- Other Identifier
- 223; 991014632556704721