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Array Geometry Based Beamforming in Smart Antennas Intended for Capacity Improvment in Wireless Systems

Poormohammad, Sarah | 2019

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 51952 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Farzaneh, Forouhar
  7. Abstract:
  8. Novel two dimensional and three dimensional antenna array geometries for smart antenna application are introduced. MMSE beamforming algorithm, using these arrays, in presence of signal, noise and interferences is implemented. Beamforming approach is used for every type of array assuming uniform and log-normal distributions for the interference amplitudes. Equal volume cylindrical or prism type arrays with circular, hexagonal, triangular, square and star cross sections with equal number of elements are considered for comparison. Novel geometries consisting of rotated cross sections are studied as well. In each case the relative SIR’s are compared in these geometries, showing that the triangular and the star cross section prisms have a better performance with respect to other cylindrical geometries. Monte-Carlo simulations show that the rotated geometries have a better performance with respect to the conventional 3D geometries both in terms of direction finding resolution and SIR values. The mutual coupling effect is included by changing the search vector in the MUSIC DOA algorithm for novel 3D geometries. A simple straight forward method is used which does not need complex electromagnetic computations. Simulations show that the proposed method can successfully account for the mutual coupling effects in two dimensional direction finding (both azimuth and elevation angles) with novel 3D array geometries. An analytical and low cost computational antenna array beamforming method in the presence of mutual coupling has been proposed. Mutual coupling effects is taken under consideration through the induced EMF method and the concept of active element pattern. After establishing the corresponding optimization problem, the desired beamformer is obtained through solving a convex optimization problem. At the end, the 3D array of half-wave dipole elements, in different geometries are compared based on the SIR criterion Elliptical cylinder, truncated sphere and random cylindrical geometries are studied in terms of DOA estimation and beamforming efficiency. In each case the corresponding geometry is compared to the normal cylindrical geometry with the same volume and the same number of elements. The efficiency of each geometry is verified through Monte-Carlo simulations. It is shown that the elliptical cylinder geometry has a better performance for non-uniform traffic distribution in azimuth and the truncated sphere geometry has a better performance where the traffic is confined in elevation. The random cylindrical geometry has a better performance in uniform traffic distribution in azimuth and elevation, all with respect to the normal cylindrical geometry.Given the performance evaluation of these arrays in terms of direction finding resolution and beamforming precision, smart antenna realization becomes plausible with these novel geometries for practical purposes
  9. Keywords:
  10. Smart Antenna System ; Beam Shaping ; Radio Direction Finding ; Array Geometry ; Mutual Coupling ; Signal to Interference Ratio

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