Research On Antenna Array For Co-Time Co-Frequency Full-Duplex EM Communications

With the explosive increment of information and data exchange,the traditional half-duplex mode has been unable to meet the needs of communication development.Improving the spectrum efficiency and increasing the efficiency of time resource allocation are the key factors for the next-generation wireless network that characterizes higher data and throughput.Compared with the traditional frequency-division or time-division duplexing systems,Co-time Co-frequency full duplexing(CCFD)wireless communication theoretically has the potential to double the spectral efficiency by simultaneously transmitting and receiving information with the same carrier.The most challenging work is to avoid self-interference between the local transmitter and receiver.However,due to all kinds of tolerances of the actual components,eliminating the self-interference is difficult when only resorting to the analog and digital domain.Therefore,realizing high transmit-receive(Tx-Rx)isolation at the antenna level is important to promote the CCFD communication towards practical applications.This work takes the antenna array research of CCFD electromagnetic communication as the research topic.The universal full-duplex feeding network together with CCFD antenna array centered 5.8 GHz for the ISM band application is analyzed and developed as well as demonstrated in principle.The main research contents of this work include:Firstly,the current research background of CCFD wireless communications at the antenna level is reviewed.Methods including separation of transceivers,null/closerange field cancellation,antenna pattern withering,and improved feeding networks are summarized.Secondly,based on the side-fed patch antenna,a full-duplex feeding network with differential feeding is discussed.Relationship between the self-interference suppression level and the phase and amplitude imbalances is analyzed.Thirdly,a dual-circularly polarized antenna array with high isolation is studied.A dual-linearly polarized antenna array is designed by using branch line balun.Furthermore,a full-duplex feeding network for circular polarization is developed to achieve high isolation for the Tx-Rx terminal at the antenna array level.Fourth,a broadband high isolation dual-circularly polarized antenna array is developed.Based on the full-duplex feeding network,a 2×4 ring-shaped dual-circularly polarized antenna array is presented.The operation bandwidth of the antenna array is further enhanced,and broadband high isolation is realized.To verify the study,simultaneous dual-side video transmissions are carried out experimentally.Fifth,a narrowband high isolation dual-circular polarization antenna array is studied.In order to further enhance the isolation characteristics between the local Tx-Rx terminal,this work designs a high isolation four-port device based on the slot-line and a universal full-duplex feeding network.A 2×2 dual-circularly polarized antenna array is realized to achieve high isolation and good axial ratio in a narrow band.The last chapter of this thesis is the summary of the work and the future development trend of CCFD antenna array technology.