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Ultrasound has been extensively used and investigated in medical applications, such as medical imaging [1] and drug delivery [2], because of advantages such as noninvasiveness, good penetration, good sensitivity, and ease of use. Prior to the development of piezoelectric micromachined ultrasound transducers (pMUTs), conventional transducers were made of piezoelectric ceramics, such as lead zirconate titanate [3]. These materials when operated in thickness mode exhibit a large impedance mismatch between the transducer surface and medium resulting in lower bandwidth unless augmented with one or more matching layers. With the development of MEMS technology, improvements in MUTs have been realized in several aspects, such as wide bandwidth without the addition of matching layers [4], smaller cell size, therefore higher operating frequency and better resolution, and easier fabrication of large arrays at lower cost [5]. Despite lower electromechanical coupling coefficient, the low-power consumption feature makes pMUTs good candidates for a variety of applications, including intrabody communication [6] and fingerprint sensing [7].
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Broadband impedance matching for lossy magnetic metamaterials in conductive media
Abstract We present a broadband impedance matching model for traveling waves on lossy magnetic metamaterials known as magnetoinductive waveguides (MIWs) in conductive media. Thus far, broadband impedance matching has only been demonstrated in the case of a lossless MIW in free-space due to complexities introduced by losses and eddy current effects. As such, current studies in conductive environments have been limited to utilizing narrow-band matching techniques or relying on attenuation to mitigate reflections, thus limiting the system performance in terms of bandwidth and transmission loss. The proposed model overcomes these limitations by utilizing the nearest neighbor coupling and binomial approximations to generate transducer design criteria in terms of equivalent circuit parameters for broadband impedance matching. To validate the model, a transducer is designed for a 40-MHz lossy MIW submerged in an ocean water phantom. Reflection coefficient results demonstrate a 15.5% fractional bandwidth and a maximum value of − 9.0 dB in the propagation band of the MIW, indicating excellent performance. This model expands the potential design space of MIWs to include complex environments such as underwater, underground, or on the human body.
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- Award ID(s):
- 2053318
- PAR ID:
- 10621500
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Scientific Reports
- Volume:
- 15
- Issue:
- 1
- ISSN:
- 2045-2322
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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