• Title/Summary/Keyword: S-parameter circle-fit

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A Comparative Study on the Effective Surface Resistance of High-$T_c$ Superconductor Films as Measured by Using the S-parameter Circle-fit and the Lorentzian-fit Methods (S-parameter Circle-fit과 Lorentzian-fit 방법으로 측정된 고온초전도체 박막의 유효표면저항 비교)

  • Kim, Min-Jeong;Jung, Ho-Sang;Lee, J.H.;Lee, Sang-Young
    • Progress in Superconductivity
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    • v.9 no.2
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    • pp.146-151
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    • 2008
  • Measurements of surface resistance ($R_s$) of high temperature superconductor (HTS) films with accuracy are essential for microwave applications of HTS materials. In using the dielectric resonator method, uncertainties in the unloaded quality factor of the resonator cause significant errors in the measured $R_s$ of HTS films. We compare the Rs values of $YBa_2Cu_3O_{7-{\delta}}$ films calculated from the $Q_0$ as determined from the Lorentzian fit with that from the $Q_0$ as determined from the S-parameter circle-fit at temperatures between 15 K and 77 K. The two sets of values appeared to differ by 5%, 7%, 6%, and 11% at temperatures of 15, 60, 70, and 77 K, respectively, from each other, implying that careful error analysis needs to be performed in obtaining the $R_s$ of HTS films by using the Lorentzian-fit method, with the ones determined from the S-parameter circle-fit used as the reference.

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Comparative Study for the Unloaded Quality Factors of High-Tc Superconductor-Dielectric Resonators Measured by Using S-parameter Circle-fit Method and Lorentzian-fit Method (S-parameter circle fit 방법과 Lorentzian fit 방법으로 측정된 고온초전도 유전체 공진기의 Unloaded Quality Factor 비교)

  • Kim, M.J.;Lee, J.H.;Park, E.K.;Yang, W.I.;Jung, H.S.;Choi, Y.O.;Lee, S.Y.
    • Progress in Superconductivity
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    • v.8 no.2
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    • pp.143-151
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    • 2007
  • Accurate measurements of the microwave surface resistance (Rs) of high temperature superconductor (HTS) films are important with regard to applications of HTS materials for wireless communications. As the surface resistance values of HTS films are usually extracted from the measured unloaded quality factor ($Q_0$) of resonators made of HTS films, it is essential to measure the resonator $Q_0$ with accuracy. The $TE_{011}\;mode\;Q_0$ of sapphire resonators with the endplates made of $YBa_2Cu_3O_{7-{\delta}}$(YBCO) film on $LaAlO_3$ is measured by using the S-parameter circle-fit method at a frequency of about 19.6 GHz and temperatures of 30 K to 90 K, which is compared with the measured values by using the Lorentzian-fit method. Good agreements are found between the two sets of $Q_0$ values measured by using the two different methods whether the resonator is used in a weak-coupling scheme or a strong-coupling scheme, showing reliability of both methods fur measuring the resonator $Q_0$ accurately. The $Q_0$ of sapphire resonators with a gap between the top plate and the rest of the resonator is also discussed.

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