Research And Design Of Frequency And Polarization Reconfigurable Antenna

In recent years,with the rapid development of communication systems,radar and wireless communication technologies,the electromagnetic compatibility deterioration problem caused by the increasing number of antennas on the carrier platform is more and more serious.Reconfigurable antennas have significant advantages in solving this problem.They can change one or more electrical parameters of the antenna in real time according to the change of the environment,so that the antenna has the ability of reconfiguration,and replace multiple antennas with one antenna.In this way,the deterioration of electromagnetic compatibility on the carrier platform can be alleviated.Up to now,reconfigurable antennas have been concerned in many aspects,such as radar detection,target recognition,satellite communication and so on.The application prospect is very considerable.In this thesis,two kinds of frequency reconfigurable antennas and two kinds of hybrid reconfigurable antennas have been designed.The main contents are summarized as follows:(1)A novel tri-band reconfigurable microstrip patch antenna has been proposed.By controlling the on-off state of the two PIN diodes,the effective electric length of the antenna can be adjusted,so as to achieve the purpose of frequency reconfiguration.The antenna prototype is fabricated and measured.The results indicate that the proposed antenna can be flexibly switched between three bands of 10.9-11.18 GHz,15.65-15.9 GHz and 32.3-33.6 GHz with stable radiation patterns.(2)The reconfiguration of broadband circularly polarized antenna is studied.Firstly,a wide-band circularly polarized cross dipole antenna with frequency reconfigurability is proposed based on its wide-band characteristics.By controlling the four pin diodes embedded in the dipole arm,the flexible switching between the three frequency bands is realized,and the stable radiation characteristics and high gain characteristics can be maintained in the three frequency bands.The antenna prototype is fabricated and measured.The results show that the antenna has wide 3 d B axial ratio bandwidth(34.7%,15.4%,4.16%)and-10 d B impedance bandwidth(63%,59.4%,12.5%)in each state.Secondly,in order to further expand the function of the antenna,a broadband cross dipole antenna with both frequency and polarization reconfigurable is proposed.By controlling the on-off state of the PIN diode at the feed connection,the antenna can switch between LHCP and RHCP.By further controlling the on-off state of PIN diode embedded in each arm of cross dipole in each polarization state,the switchable working frequency band has been realized.(3)A kind of antenna which can realize the compound reconfiguration of polarization and pattern is proposed.The novel feature of the antenna is that the polarization and pattern of the antenna can be controlled separately,and the polarization reconfigurability can be achieved by truncating the four corners of the driving antenna.Besides,the reconfigurability of the pattern can be achieved by using the pixel surface as the electromagnetic coupling parasitic element provider around the same layer of the driving antenna.The simulation results show that the antenna can switch between three different polarizations,and in each polarization state,the main beam can be deflected by using the reconfigurable parasitic pixel layer.The antenna does not need any phase shifter,and can be implemented easily,enabling the antenna has simple and compact structure and low cost.