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Characteristic Mode Theory and Its Applications in the Researches of Pattern Reconfigurable Antennas

Author: WuZuoXia
Tutor: WangBingZhong
School: University of Electronic Science and Technology
Course: Radio Physics
Keywords: characteristic mode pattern reconfigurability the method of moment (MOM) electrically small antenna
CLC: TN820
Type: PhD thesis
Year: 2005
Downloads: 476
Quote: 2
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Abstract


This dissertation is mainly focused on the characteristic mode theory and its applications in the analysis and design of pattern reconfigurable antennas.In Chapter 1, the research background and recent developments about the pattern reconfigurable antenna are reviewed. The main works and contributions of this dissertation are outlined.In Chapter 2, an approach, entire equivalence current integral equation is introduced for the analysis of microstrip antennas. The equivalence principle is used to replace all conducting bodies by equivalent surface electric currents and all dielectrics by equivalent volume polarization currents. The respective boundary conditions on the dielectric and the conductor are utilized to build the integral equations and MOM is utilized to solve the electric current on the entire structure.In Chapter 3, a theory of characteristic modes of conducting bodies is introduced and a method of characteristic mode excitation has been studied according to modal excitation factor. The mode currents form a weighted orthogonal set over the conductor surface, and the mode fields form an orthogonal set over the sphere at infinity. The characteristic modes used as basis functions bring impedance matrix diagonal in applications such as analysis of radiation and scattering. For electrically small and intermediate size bodies, only a few modes are needed to characterize the electromagnetic behavior of the body.In Chapter 4, the predominant five characteristic currents and the corresponding characteristic patterns of a diversity wire antenna with two highly-isolated ports are given. The expanded coefficients of the two port currents reveal that the antenna’s patterns and the currents can be approximated by weighted linear combination of the first two characteristic modes. And the first two characteristic modes can be excited according to modal excitation factor.In Chapter 5, a pattern reconfigurable planar fractal antenna is presented. The top square fractal patch area of the antenna is 15mm × 15mm, which is smaller than 0.5λ×0.5λ at 8.4GHz. Simulated and measured results show that four switchable directional patterns in the x-z and y-z planes respectively are achieved by changing the connection states of the switches. The pattern reconfigurablity of the planar fractal

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CLC: > Industrial Technology > Radio electronics, telecommunications technology > Radio equipment,telecommunications equipment > Antenna > General issues
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