Study On Technologies Of Isolation Enhancement Between Multiple Antennas On Co-platforms

With the rapid development of modern wireless communication technology,higher requirements have been put forward for the antennas and their arrays which act as the radio frequency front-end transceiver devices.On the one hand,along with the development trend of miniaturization for the multiple-input multiple-output（MIMO）and multiple antenna systems,the center-to-center spacings between adjacent antenna elements become more and more smaller that leads to high mutual couplings between antenna elements.In order to ensure the original impedance and radiation characteristics of the antenna system,one should develop decoupling method for compact antenna arrays to enhance the isolation levels between the antenna ports.On the other hand,for the full-duplex transceiver system,the coupling between the transceiver antennas may cause the system to fail to work properly no matter whether the transceiver antennas are placed in the near field or far field of each other.Therefore,the decoupling method for transceiver antenna system is also an urgent technology to be developed in modern wireless communication system.Based on the above background,this dissertation developed the isolation enhancement technologies between multiple antennas with common platforms.The main works are as follows:（1）A decoupling method for compact circularly polarized antenna array based on based on multipath coupling cancellation theory is proposed.The hybrid near field parasitic resonators were developed for the decoupling of compact circularly polarized slot-coupled patch antenna array based on the developed circularly polarized antenna array decoupling method.The-10 d B working frequency band of the antenna array covers the range 2.4-2.7 GHz,and the 3 d B axial ratio working frequency band also covers the range 2.4-2.7 GHz.On the other hand,the center-to-center spacing between adjacent antenna elements of the circularly polarized array was selected to 0.5λ₀.The simulation results show that the coupling between the adjacent circularly polarized antennas can be reduced by more than 12.7 d B over the entire operational frequency band by introducing the developed hybrid parasitic decoupling structure.In the meantime,the developed hybrid decoupling structure has little effect on the radiation characteristics of the circularly polarized array.This results verified the effectiveness and polarization insensitivity characteristics of the developed hybrid near-field parasitic resonant decoupling structure.（2）A swastika-shaped near-field parasitic resonant decoupling structure is developed for the decoupling of compact wideband circularly polarized dipole array based on the developed circularly polarized array decoupling method.The-10 d B operational frequency range of the developed circularly polarized dipole antenna array covers 1.7-2.7 GHz,and the center-to-center（edge-to-edge）spacing between the adjacent elements is 0.4λ₀（0.024λ₀）.The developed swastika-shaped element yields an increase of the isolation level between the circularly polarized antenna elements of more than 9.4 d B over the entire operational band,with a maximum improvement of 20.4 d B.Moreover,the antenna elements realize a modest maximum gain improvement of～1.2d B in the boresight direction over the same band.The radiation characteristic of the decoupling array keeps well over the entire operational frequency band.Furthermore,the developed decoupling method has been confirmed to be applicable to both diamond and rectangular larger scale antenna arrays.（3）A decoupling method for compact dual-polarized antenna array based on based on multipath coupling cancellation technique is proposed.Two types of near-field parasitic resonant decoupling structures have been developed.They are the meander line structures for E-plane port coupling and the H-shaped structure for H-plane port coupling.The-10 d B operational frequency band of the dual-polarized decoupling antenna array covers the range 2.4-2.7 GHz,and the center-to-center spacing between adjacent antenna elements is 0.5λ₀.The coupling levels between the E-plane（H-plane）coupled ports was reduced by more than 11.7 d B（9.24 d B）over the entire operational frequency band by introducing the developed the hybrid decoupling structure.Moreover,the developed hybrid decoupling structure has little effect on radiation performance of the antenna array.These results verified the reliability and stability of the developed decoupling method for compact dual-polarization arrays.（4）The H-shaped interdigital structure was developed for compact broadband dual-polarized magnetoelectric antenna array based on the developed dual-polarized antenna array decoupling method.The-10 d B operational frequency range of the magnetoelectric antenna decoupling array covers 1.7-2.2 GHz,and the center-to-center spacing between the adjacent elements is 0.5λ₀.The coupling levels between the E-plane（H-plane）coupled ports was reduced by more than 10.7 d B（18.8 d B）over the entire operational frequency band by introducing the developed the H-shaped interdigital decoupling structure.Moreover,the radiation characteristic of the decoupling array keeps well over the entire operational frequency band.This results validated the wideband decoupling characteristic of the H-shaped interdigital structure.（5）The method of far-field coupling reduction for wideband antenna array empowered by radiation pattern modulation is proposed.The split ring resonator（SRR）arrays are developed for the isolation enhancement of far-field coupling horn array based on the radiation modulation theory.The developed SRR arrays were applied to two types of horn antenna arrays,whose center-to-center distance is 8 m and operational frequency ranges respectively cover 8-12 GHz and 8-11.5 GHz,and resulted in significant mutual coupling reductions,i.e.,more than 28.5 d B and 28 d B,respectively.