Browsing USN Open Archive by Author "Hoff, Lars"

Now showing items 1-18 of 18

    • Acoustic Characterization of Inhomogenous Layers using Finite Element Method 

      Bolstad, Per Kristian; Manh, Tung; Frijlink, Martijn; Hoff, Lars (Peer reviewed; Journal article, 2021)
      This study presents a finite element approach to estimate acoustic parameters of layers of arbitrary compositions using 2D and 3D models. In this approach the resonance frequency of a layer to be investigated is found by ...

    • Acoustic Impedance Matching of PMN-PT/epoxy 1-3 Composites for Underwater Transducers with Usable Bandwidth Restricted by Electrical Power Factor 

      Røed, Ellen Katrine Sagaas; Andersen, Kenneth Kirkeng; Bring, Martin; Tichy, Frank; Åsjord, Else-Marie; Hoff, Lars (Peer reviewed; Journal article, 2019)
      Volume cost has limited the use of single crystals in underwater applications, butreported performance of PMN-PT sonar transducers now motivates the design of commercial prototypes. This work addresses optimization of the ...

    • Analyse av en Ultralyd Transduser med et Laser Doppler Vibrometer 

      Nilsen, Mikael Isak (Master thesis, 2021)
      Ultrasonic transducers are an integral part of underwater imaging, with a wide range of applications. In this thesis, analysis of a underwater echo sounder transducer operating at 200kHz is done underwater with a Laser ...

    • Characterization of Layers with Metal-Coated Polymer Spheres for use in Ultrasound Transducers 

      Nicolaisen, Anette Sollien (Master thesis, 2021)
      The properties of materials used in ultrasound transducers affect the properties of the finished transducer, making it important to characterize the acoustic properties of these materials. The study in this thesis is ...

    • Electrical power factor for a single crystal tonpilz versus a plate with matching layers 

      Røed, Ellen Katrine Sagaas; Bring, Martin; Tichy, Frank; Åsjord, Else-Marie; Hoff, Lars (Peer reviewed; Journal article, 2021)
      For underwater transducers mounted on small platforms, reactive electrical power can constitute a main restriction on the usable frequency range. The frequency range in which the amount of reactive power is acceptable can ...

    • Estimating Regional Myocardial Contraction Using Miniature Transducers on the Epicardium 

      Nguyen, Thu Thuy; Espinoza, Andreas Westenvik; Hyler, Stefan; Remme, Espen W.; D'Hooge, Jan; Hoff, Lars (Peer reviewed; Journal article, 2019)
      This paper describes an ultrasound system to monitor cardiac motion using miniature transducers attached directly to the epicardial surface. Our aim was to develop both a research tool for detailed studies of cardiac ...

    • Fabrication and Characterization of a Low-Frequency Array for a Hybrid PZT-CMUT Transducer 

      Siu, Hoi Yi (Master thesis, 2021)
      Piezocomposite materials consist of a periodic structure of active piezoelectric materials and passive polymer materials. Piezocomposite material is widely used in medical ultrasound transducers due to the advantages of ...

    • Heat generation in underwater transducers 

      Wild, Marcus Sebastian (Doctoral dissertations at the University of South-Eastern Norway;38, Doctoral thesis, 2019)
      Acoustic transducers are used for a variety of applications, ranging from medical to maritime uses. In the maritime sector, underwater transducers can be used for appli- cations such as seabed mapping, fishing and ...

    • Impact of High Pressures on Au-Sn Solid Liquid Interdiffusion (SLID) Bonds 

      Bolstad, Per Kristian; Kuziora, Stephane; Nguyen, Hoang-Vu; Manh, Tung; Aasmundtveit, Knut; Hoff, Lars (Chapter, 2020)
      This paper investigates the influence of high pressure on Au-Sn solid-liquid interdiffusion (SLID) bonds formed by bonding Si substrates to dies of either lead-zirconate titanate (PZT) with high surface roughness or Si ...

    • Increased Usable Frequency Band for Underwater Transducers with Single Crystal 

      Røed, Ellen Katrine Sagaas; Andersen, Kenneth Kirkeng; Bring, Martin; Tichy, Frank; Åsjord, Else-Marie; Hoff, Lars (Peer reviewed; Journal article, 2020)
      In the increasing market of transducers for small underwater platforms, each transducer should be used for several purposes, hence cover as large frequency range as possible. Bandwidth is commonly defined as the -3dB limit ...

    • Intermetallic bonding as an alternative to polymeric adhesives in ultrasound transducers 

      Bolstad, Per Kristian; Le, Anh Duy; Hoff, Lars; Manh, Tung (Peer reviewed; Journal article, 2019)
      Common ultrasound transducers utilize epoxy for bonding the active piezoelectric to the rest of the acoustic stack. This paper explores some of the potential benefits of replacing this soft epoxy layer with a harder ...

    • Low Noise Amplifier Design for Hybrid Ultrasound CMUT/PZT Probes 

      Matti, Opeyemi Saheed (Master thesis, 2023)
      This thesis focuses on the analysis and design of low-noise amplifiers (LNAs) specifically tailored for medical ultrasound imaging. The objective is to develop amplifiers that can effectively sense signals from a Capacitive ...

    • Nonlinear electrical impedance of the acoustic stack in cardiac ultrasound probe 

      Huynh, Thong; Hoff, Lars; Eggen, Trym Haakon (Peer reviewed; Journal article, 2020)
      Understanding the nonlinearity in ultrasound probes is important for tissue harmonic imaging, as 2nd harmonic components transmitted from the probe may interfere with harmonics from the tissue and degrade the image quality. ...

    • Nonlinearity in a medical ultrasound probe under high excitation voltage 

      Huynh, Thong; Haugen, Geir Ultveit; Eggen, Trym Haakon; Hoff, Lars (Peer reviewed; Journal article, 2020)
      Tissue harmonic imaging is often the preferred ultrasound imaging modality due to its ability to suppress reverberations. The method requires good control of the transmit stage of the ultrasound scanner, as harmonics in ...

    • Numerical optimization of ultrasound transducers by the linearity of the phase spectrum 

      Andersen, Kenneth Kirkeng; Frijlink, Martijn Egbert; Hoff, Lars (Journal article; Peer reviewed, 2017)
      New ultrasound imaging and therapeutic modalities may require transducer designs that are not easily facilitated by conventional design guidelines and analytical expressions. This motivates the investigation of numerical ...

    • Reduction of transmitted 2nd harmonics using an adaptive method by simulated annealing 

      Huynh, Thong; Haugen, Geir; Hoff, Lars (Peer reviewed; Journal article, 2017)
      Second harmonic imaging relies on the double the transmit frequency being generated as the waves propagate into the tissue. The method requires good control over the transmit system, to suppress 2 nd harmonics transmitted ...

    • Sources of 2nd harmonic generation in a medical ultrasound probe 

      Huynh, Thong; Hoff, Lars; Eggen, Trym Haakon (Peer reviewed; Journal article, 2018)
      Tissue harmonic imaging is often the preferred ultrasound imaging modality due to its ability to suppress reverberations. The method requires good control on the transmit stage of the ultrasound scanner, as harmonics in ...

    • Ultrasound Transducers for High Pressure Environments Up to 1000 Bar 

      Bolstad, Per Kristian; Manh, Tung; Midtseter, Nils; Frijlink, Martijn Egbert; Hoff, Lars (Peer reviewed; Journal article, 2020)
      This paper studies the influence of high ambient pressure on ultrasound transducers where the piezoelectric layer is bonded to the acoustic matching layer by two different methods: Au-Sn solid-liquid interdiffusion and ...