| 1. |
- Carlsson, Erik F., 1968, et al.
(författare)
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Conformal mapping of the field and charge distributions in multilayered substrate CPWs
- 1999
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9480 .- 1557-9670. ; 47:8, s. 1544 - 1552
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Tidskriftsartikel (refereegranskat)abstract
- Conformal mapping (CM) and partial capacitance techniques are used for analytical evaluation of charge/current and electric- and magnetic-field distributions in a multilayered substrate coplanar waveguide (CPW) in the quasi-TEM approximation. The results, compared with finite-element method simulations, show that the magnetic wall assumed at the dielectric-dielectric interfaces in CM is a good approximation for many practical cases. The method is applied to a CPW with a thin ferroelectric film used in tunable microwave devices
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| 2. |
- Carlsson, Erik F., 1968, et al.
(författare)
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Effect of enhanced current crowding in a CPW with a thin ferroelectric film
- 1997
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Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 33:2, s. 145-146
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Tidskriftsartikel (refereegranskat)abstract
- Enhanced current crowding is predicted at the edges of the conducting strips in thin ferroelectric film coplanar waveguides (CPWs). A minimum current crowding depth is expected, which depends on the CPW geometry and dielectric constant of the ferroelectric film. In practical CPW devices the enhanced current crowding can increase the conductor losses by up to four times. The current crowding depth may be smaller than the skin depth or London penetration depth (for high temperature superconducting CPW)
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| 3. |
- Carlsson, Erik F., 1968, et al.
(författare)
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Effects of package width on K-band high-temperature superconducting filters
- 1995
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Ingår i: Microwave and Optical Technology Letters. - : Wiley. - 1098-2760 .- 0895-2477. ; 10:6, s. 315-317
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Tidskriftsartikel (refereegranskat)abstract
- The effect of substrate/package width on filter performance is demonstrated and discussed for 18-GHz packaged filters using high-temperature superconducting (HTS), coupled microstrip lines. The filters are made of 0.3-μm YBa2Cu3O7 – ∂8 (YBCO) on MgO substrates with copper ground planes. The HTS filter shows a minimum insertion loss (IL) of 0.9 dB, steep skirts, and very good out-of-band rejection (> 45 dB up to 21 GHz) at 77 K with a bandwidth of 2.8% and a 0.3-dB ripple
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| 4. |
- Carlsson, Erik F., 1968, et al.
(författare)
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Electric field dependent microwave losses in KTaO3 single crystal with YBa2CU3O7-x electrodes
- 1999
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Ingår i: Ferroelectrics, Letters Section. - : Informa UK Limited. - 0731-5171 .- 1563-5228. ; 25:5-6, s. 141-152
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Tidskriftsartikel (refereegranskat)abstract
- We have measured the voltage dependence of the resonant frequency and the microwave losses for parallel-plate resonators based on single crystals KTaO3, with YBa2Cu3O7-x electrodes. The losses increase and the dielectric constant decrease monotonically with applied voltage. Both the dielectric constant and the losses show a hysteretic effect in the voltage dependence. The hysteretic effects may be explained by electric field assisted charge trapping both in the KTaO3, crystal and at the KTaO3/YBa2Cu3O7-x interfaces
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| 5. |
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| 6. |
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| 7. |
- Chakalov, R, et al.
(författare)
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Fabrication and investigation of YBa2Cu3O7-delta/Ba0.05Sr0.95TiO3 thin film structures for voltage tunable devices
- 1998
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Ingår i: Physica C: Superconductivity and its Applications. - 0921-4534. ; 308:3-4, s. 279-288
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Tidskriftsartikel (refereegranskat)abstract
- High-temperature superconducting/ferroelectric thin film structures were deposited by laser ablation. Three types of voltage tunable devices were fabricated and investigated-trilayer capacitor, planar interdigital capacitor and coplanar waveguide. As ferroelectric the solid solution BaxSr1-xTiO3 was chosen with barium content x = 0.05 because its Curie temperature is close to the liquid nitrogen boiling point (77 K). Temperature and voltage dependences of the Ba0.05Sr0.95TiO3 dielectric constant epsilon(r,BSTO) were studied. High epsilon(r,BSTO) values were determined-up to 3000 at 75 K, 20 GHz and zero de bias. Efficient voltage tunability was demonstrated (up to 40%) at loss level tan delta=0.01-0.1. Compact YBa2Cu3O7-delta/Ba0.05Sr0.95TiO3 coplanar waveguide with as narrow gap as 18 mu m was tested as electrically tunable phase-shifter and field-induced phase shifts of more than 180 degrees were obtained by 35 V de bias at 20 GHz. This improvement was attained by proper choice of the ferroelectric material, accomplished epitaxial growth of the films and decrease of the specific dimensions. (C) 1998 Published by Elsevier Science B.V. All rights reserved.
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| 8. |
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| 9. |
- Gevorgian, Spartak, 1948, et al.
(författare)
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Asymmetric Coplanar-Strip Transmission Lines for MMIC and Integrated Optic Applications
- 1990
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Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 26:22, s. 16 - 1918
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Tidskriftsartikel (refereegranskat)abstract
- Microwave transmission lines with coplanar electrodes on dielectric or semiconductor substrates are widely used in integrated optic travelling-wave modulators and optical control microwave attenuators/modulators. The reduction of the drive voltage in travelling-wave modulators and control power in optical control microwave attenuators is achieved by reducing the width of the gap between the coplanar strips. When reducing the gap width in these devices special care must be taken to keep the characteristic impedance, Z0, high. Although symmetric coplanar and coplanar-strip waveguides, have been used, asymmetric coplanar-strip waveguides seem to be highly flexible in practical device design. Along with small sizes, the impedance, Z0, effective dielectric constant, in e, and microwave refractive index, nm, can be adjusted by changing the width of one of the strips while keeping the width of the other strip and of the gap fixed. The basic parameters ( in e,C,Z0) of asymmetric coplanar-strip waveguides on finite thickness substrate are reported.
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| 10. |
- Gevorgian, Spartak, 1948
(författare)
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Basic characteristics of two layered substrate coplanar waveguides
- 1994
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Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 30:15, s. 1236 - 1237
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Tidskriftsartikel (refereegranskat)abstract
- The conformal mapping technique is used to obtain simple CAD oriented closed form expressions for the effective dielectric permittivity, line capacitance and impedance of two layered coplanar waveguides (CPWs)
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