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Full Analysis Antenna Ferrite Disk in Range of Negative Permeability

Ahmadvand, Ahmad | 2015

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 46835 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Rejaei, Behzad
  7. Abstract:
  8. In wireless communication systems increasing the gain of antennas is seminal to increase in coverage and data transmission rate, and reducing the possible errors. One of the main factors for improving the antenna gain is matching the polarizations of the transmitter and the receiver antennas. Towards this end, both the transmitter and the receiver antennas should have the same axial ratio, specific direction and polarizations. As far as the flexibility of the direction angle between the transmitter and the receiver is concerned, the so-called circular polarization is preferred do the linear polarization. The antennas with circular polarizations are prominently utilized in satellites, frequency identification, global positioning and wireless local area network systems. One way to achieve the properties of this type of antennas is using the gyrotropic properties of ferrite. This study intends to examine a cylindrical ferrite antenna, the top surface of which is covered with a metallic coating and further placed on the ground. The device utilizes the resonant modes of the disk which rotate only in the clockwise or counter clockwise sense in the frequency range where the effective permeability of ferrite is negative. The antenna is capable of keeping the axial ratio less than 3 dB, and has the angular range of 90° with an operation frequency which can be tuned in the 4-4.5 GHz range by varying the magnetic bias field from 50 to 35000 A/m. According to the pertinent literature, this investigation aims to provide a complete analytical method for this structure, so that the changes of the field in the antenna axis is considered and the impact of higher emission modes for larger antenna height are examined
  9. Keywords:
  10. Gyrotropic Materials ; Magnetic Permeability Tensor ; Antenna with Circular Polarization

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