Design Of Reconfigurable Magneto-electric Dipole Antenna

With the rapid development of mobile communications,more requirements for high data rate and high reliability of wireless communication systems are proposed.More and more systems require multiple radio frequencies integrated under one platform to ensure maximum connectivity.With the introduction of the reconfigurability concept into the antenna,antenna behavior can be adjusted according to the changing system requirements or environmental conditions.Hence,the performance of the system can be improved,and some restrictions on the system can be eliminated,and various functions for the system can be provided.It can be seen that reconfigurable antennas have many advantages such as avoiding noise sources,improving channel capacity,increasing radiation coverage,avoiding multipath fading effects,and improving system stability.Therefore,the designs of reconfigurable antennas have attracted increasing attentions in recent years.In addition,a new type of antennas called Magneto-electric(ME)dipole antenna was proposed by Luk to demonstrate outstanding characteristics.The conventional ME dipole antenna consisting of both electric and magnetic dipoles can achieves 43.8%impedance matching bandwidth.Moreover,in the operating bandwidth,the ME antenna has high and stable gain.At the same time,the antenna pattern also is of low back lobe and low cross polarization.Hence,the ME dipole antenna has a huge potential application in the field of the mobile communication.On the basis of the above research background,three kinds of reconfigurable ME dipole antennas are designed,including reconfigurable pattern,reconfigurable polarization and reconfigurable frequency.The main innovations of this thesis are summarized as follows:1.A novel beamwidth reconfigurable ME dipole antenna is designed.By controlling the capacitances of the varactor diodes,the coupling between the parasitic patches and the ME dipole antenna are manipulated,and thus the beamwidths of the proposed antenna in the E-and H-planes can be flexibly tuned.Compared with previously reported ME dipole antennas with the reconfigurable beamwidth,the proposed ME dipole is capable of achieving tunable E-plane and H-plane beamwidths either individually or simultaneously.Measured results demonstrate that the beamwidth of the antenna can be tuned about 50~o in the 2—2.1GHz band.2.A novel frequency reconfigurable ME dipole antenna is proposed.By changing the capacitance of the varactor diodes,the electric field distribution of the magnetic dipole in the rectangle waveguide is adjusted,and the working frequency can be continuously tuned in a frequency band with a stable pattern characteristic.Simulation results show that the proposed antenna can be continuously tuned in a frequency band from 3.49GHz to 5.8 GHz.And the antenna radiation pattern achieves a front-to-back ratio of more than 15 dB and cross-polarization of less than-40 dB.3.A polarization reconfigurable ME dipole antenna is designed.By switching the diode state between“OFF”and“ON”,the horizontal patches can be connected or disconnected,and thus the linear polarization(LP),left-handed circular polarization(LHCP),and right-handed circular polarization(RHCP)waves can be excited,respectively.Compared with the previously proposed polarization reconfigurable electromagnetic dipole antenna,the proposed antenna achieves a relative effective overlap bandwidth of 33.9%with a simple structure and achieves a stable gain of about 8.2dB in the effective bandwidth.