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Nonlinearity in Superconducting Microwave Planar Structures

Javadzadeh, Mohammad Hassan | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 44437 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Farzaneh, Forouhar; Fardmanesh, Mehdi
  7. Abstract:
  8. Nowadays superconducting devices and especially high temperature superconductors (HTSs) have found very wide applications in microwave engineering. This technology is raised in the form of planar microwave structures and in the different shapes of superconducting microstrip transmission lines, strip lines and coplanar waveguide (CPW) lines and different kind of applications like resonators, couplers, filters, antennas, etc. Important advantage of these structures is very low loss, small size and high quality factor. However nonlinear behavior of superconducting microwave devices, due to the dependence of the surface impedance on the applied field, limits the power handling capability of these devices which needs special considerations. These limitations might be eased if engineers could reliably predict the nonlinear effects in their designs. Moreover, some applications use this nonlinearity in a desired way which it also needs to the prediction of the kind and the value of the nonlinearity. Hence nonlinear phenomenon in superconducting microwave devices is studied. In this thesis we analyze and model the nonlinearity in some superconducting microwave planar structures same as uniform and nonuniform transmission lines, different kind of discontinuities like step in width, parallel coupling, bending, gap, open end and finally modeling the nonlinearity of superconducting microwave resonators and filters based on distributed circuit models. Therafter with Harmonic Balance analysis of the deduced circuit models, by using traditional softwares, nonlinear parameters like harmonic generation and intermodulation distortion are predicted. Validation of our proposed modeling results are confirmed by comparison with results obtained from measurements or full wave electromagnetic numerical methods. For confirmation of the proposed nonlinear models for spiral resonators, a superconducting spiral filter has been fabricated and linearly and nonlinearly has been measured at liquid helium temperature. Additionally, two new applications of nonlinearity in superconducting microwave structures like superconducting parametric amplifier and microwave kinetic inductance detectors (MKIDs) is studied and presented at the end
  9. Keywords:
  10. Nonlinear Modeling ; Superconducting Nonlinear Effects ; Superconducting Microwave Planar Structure ; Nonlinearity ; Distributed Circuit Model ; Superconducting Transmission Line Discontinuities

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