Browsing by Subject "Material characterization"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    Bi-angular lens for material characterization
    (IEEE, 1994) Yaralıoğlu, Göksen Göksenin; Atalar, Abdullah; Köymen, Hayrettin
    In this paper a new lens design is proposed for characterization of layered materials. Lamb wave lens employs Lamb waves for this purpose since these waves propagate along interfaces. However, below cut-off angle, the critical angles of Lamb wave modes are low and the generated V(z) curves have small number of oscillations, which in turn causes measurement difficulties and accuracy degradation. Bi-angular lens described in this paper, generates an extra obliquely incident wave, instead of normally incident beam, in order to provide the reference specular reflection. Simulation results as well as experimental results are presented and it is shown that a high sensitivity can be obtained by using this new lens.
  • Thumbnail Image
    ItemOpen Access
    Simple and high-sensitivity dielectric constant measurement using a high-directivity microstrip coupled-line directional coupler
    (IEEE, 2022-06-23) Rahimian Omam, Zahra; Nayyeri, Vahid; Javid-Hosseini, Sayyed-Hossein; Ramahi, Omar M.
    Simple methods using a microstrip coupled-line directional coupler (CLDC) are presented for dielectric constant measurements. The material under test (MUT) is placed on the coupled-line section of the coupler, and either the coupler’s coupling ( |S31| ) or its isolation level ( |S41| ) is considered as the sensor’s response. Putting different MUTs on the microstrip line leads to a change in the effective dielectric constant of the structure and consequently causing a change in the coupling coefficient. In addition, since the isolation level of a microstrip coupled-line coupler depends on the phase velocity difference between the substrate and the medium above the signal strips, putting different MUTs on the line significantly changes the isolation level. This change is significantly greater than the change in |S21| level of a microstrip line when loaded with different MUTs. Validation of the method is presented through measurements for both solid and liquid MUTs.