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Analysis and Design of Nonreciprocal Devices Based on Unidirectional Modes in Ferrite Waveguides

Jafarizadeh, Mohammad Mahdi | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57318 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Memarian, Mohammad; Rejaei, Behzad
  7. Abstract:
  8. Non-reciprocity in electromagnetics has been used in the design of various devices for microwave frequencies to optics. Non-reciprocity at radio frequencies and microwaves has thus far been mainly achieved by a group of magnetic materials. Ferrites are a very suitable option due to their low magnetic losses and high electrical resistance, and utilized in design and manufacture of isolators, phase shifters, absorbers and circulators. Many methods have been introduced up to now for the implementation of isolators and circulators, which have led to the construction of devices with different dimensions and characteristics . Waveguide structures whose cross section is partially filled with ferrite, within a certain frequency range and with a suitable magnetic bias, can carry one-way modes so that their dispersion diagram contains only one propagation constant. These non-reciprocal one-way modes are the motivation for this research. The goal here is to design and build a suitable isolator at microwave frequencies by using these one-way modes. Due to the propagation behavior of these modes, the main advantage of the isolators resulting from this research is their much smaller dimensions, compared to other conventional solutions . In this thesis, questions such as how the phase and amplitude of the electric and magnetic fields the one-way modes are distributed, different simulations of the structure, the design of suitable matching circuits and solving the implementation and construction problems have been addressed. During this research, we examine a rectangular waveguide structure as well as a two parallel plate structure, and explore the one-way wave inside them. Analyzing and solving the dispersion equations, extracting the dispersion and impedance parameters, designing the matching circuit suitable for connecting to the 50 Ohm line with three methods, designing the optimal parameters of the structure, implementing and measuring two prototypes, and reviewing the challenges and experiences of this process, comprise the steps taken in this thesis . As a result, the isolator designed in this research is much smaller than the conventional solutios available with a higher isolation level, and provides a higher ability to be integrated with planar microwave circuits
  9. Keywords:
  10. Nonreciprocal Magnetic Devices ; Magnetic Materials ; Ferrite ; Unidirectional Waves ; Isolator Design ; Microwave Components

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