Design Of Reconfigurable Planar End-fire Antennas

With the continuous development of radio technology,reconfigurable antennas have received more and more attention due to their ability to change operating frequencies,polarizations and radiation patterns.The planar structure antennas are popular because of their low profiles,light weights,and easy integrations with other devices.Due to the demand for end-fire antennas in certain special occasions,planar end-fire antennas are also popular due to their special radiation characteristics.Antennas can obtain better radiation characteristics by combining the advantages of reconfigurable antennas and planar end-fire antennas,which have potential application values in wireless communication systems in the future.Therefore,in this thesis a tri-polarization reconfigurable planar end-fire antenna and a frequency reconfigurable planar end-fire circular polarized antenna are designed and implemented.The main contributions of this thesis are summarized as follows.1.A tri-polarization reconfigurable planar end-fire antenna is proposed.Electric dipole Yagi element and magnetic dipole Yagi element provide two orthogonal electric field components.By adding a 270°phase delay line,the proposed antenna radiates circular polarization（CP）electromagnetic waves in the unidirectional end-fire direction.Four PIN diodes are inserted at joints of the electric dipole and the phase delay lines,and three states,left-hand circular polarization（LHCP）,right-hand circular polarization（RHCP）and vertical polarization（VP）can be switched.Coupling micro-strip patches are introduced between the driven element and the director element of magnetic dipole Yagi element to strengthen the coupling between them,therefore bandwidth of the antenna can be improved.The measured and simulated results validate performance of the proposed antenna.The experimental results demonstrate that the proposed antenna has a effective bandwidth of 7.37%from 5.62 to 6.05 GHz for both|S₁₁|≤-10 d B and axial ratios less than 3 dB at all polarization states.2.A frequency reconfigurable planar end-fire circular polarization antenna is proposed.The substrate integrated waveguide opening cavity is used to provide the vertical polarization.Two additional metallized vias are added inside the half-mode substrate integrated waveguide resonant cavity.The connection status between these two metallized vias and the upper as well as lower patches of the substrate integrated waveguide can be manipulated by the switch states of four diodes.Thus,frequencies of the vertically polarized antenna can be controlled.Along with the fixed electric dipole and phase compensation line,the end-fire antenna element can work at circular polarization states.The measured results validate performance of the proposed antenna.Measurement results show that the proposed antenna can be tuned to operate in either 5.22-5.32 GHz band or6.03-6.17 GHz band with similar radiation patterns,less than-10d B reflection coefficients and less than 3d B axial ratios.Measured gains of the antenna at 5.27 GHz and 6.1 GHz are3.0 dBic and 1.7 dBic,respectively.