Ultrasonic transducers have been widely used in the medical applications. High frequency array transducers have recently attracted many research interests, since it provides not only the electronic beamforming but also the very fine image resolution. The transducers are usually either annular or linear arrays. This study concentrates on the design of both types of array in high frequency applications. The annular array is firstly investigated, and an optimized design of array geometry is developed including the kerfs influence which is usually neglected in the design of high frequency arrays. The improved imaging performance is found by this optimized design. More interestingly, the conventional annular array with element having the same surface area has a relatively large sidelobe closest to the main lobe. Two methods are applied to suppress the sidelobe. The method of using high-impedance single matching to enlarge the element bandwidth only shows very limited lobe suppression, however, a novel matching approach is found. Another method of changing the array geometry from equal area elements to equal width ones successfully suppressed the sidelobe. The imaging results suggest that the novel equal width array shows a good improvement. The linear array is then analyzed. The kerfs influence again is found to be significant for the array especially for high frequency. It is essential to use a high attenuated kerfs material in the linear array design. More importantly, the limitation of current fabrication techniques forces the linear array to concede a high grating lobe in the imaging field if it operates in a relatively high frequency. A novel linear array is developed to suppress the grating lobe without using advanced fabrication techniques. The imaging results show that the novel linear array has a general reduction of -6dB for the lobe suppression. The novel design made the linear array operate in a very high frequency without strong grating lobe, and the array can be fabricated by current techniques.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:560506 |
| Date | January 2011 |
| Creators | Qian, Yichen |
| Contributors | Harris, Nicholas ; Beeby, Stephen |
| Publisher | University of Southampton |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://eprints.soton.ac.uk/336225/ |
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