| With the rapid development of the fifth-generation mobile communication technology and the continuous iteration of the intelligent interconnection technology of all things under the background of the new era,the requirements of communication systems for channel capacity and data transmission speed are increasing day by day.Under such demand and background,MIMO(Multiple-Input Multiple-Output,Multiple-Input Multiple-Output)technology plays an increasingly important role in communication channel transmission.MIMO technology can greatly increase the data transmission rate and channel capacity without increasing the transmission power and frequency bandwidth,so it can be well applied to complex multipath environments.As the terminal of the communication system,the MIMO antenna has also become an indispensable part of the new generation of mobile communication system.However,in the constant construction space,the increase in the number of antenna elements brought about by MIMO technology will inevitably lead to the reduction of the antenna spacing,which causes the most significant problem of mutual coupling.Antenna mutual coupling will not only cause problems such as port mismatch and radiation pattern distortion,which will seriously affect antenna performance,but also mutual coupling will worsen the low correlation between MIMO channels and affect the improvement of system capacity.Therefore,the high isolation requirement between antenna ports makes decoupling technology one of the key technologies in MIMO antenna research.In view of the technical requirements of 5G base stations for MIMO antennas,this paper mainly carried out the research on the decoupling method between multiple ports in the close-spaced dual-polarized MIMO antenna array,and proposed a new decoupling method based on the principle of sub-array-unit coupling energy cancellation.And it has been well applied in antenna arrays of different bandwidths,different spacings and different sizes.The specific content is as follows:1.Research on decoupling method of dual-polarized MIMO antenna based on subarray-element coupling cancellation.A new decoupling method based on sub-array-unit coupling cancellation is proposed,which uses two units in a sub-array to generate two coupling paths to adjacent sub-array units(or hetero-polarized units in sub-arrays)respectively.Loading the grounded metal stub at a specific position generates perturbation to the energy of the two coupling paths,so that the equal amplitude and phase phase are cancelled,and the decoupling effect between the ports is realized.Specifically,through the coupling analysis of the 2×2 fourport dual-polarized antenna array,it qualitatively and quantitatively reveals the principle of offsetting the coupling energy under the theory of this method.A simple planar decoupling structure is designed,and three simple decoupling structures are used.Simultaneous loading can effectively reduce the intra-sub-array hetero-polarization coupling and the inter-sub-array coupling with the same polarization among the multiple ports in the array.Finally,in order to verify the feasibility of the scheme,the proposed high isolation antenna array was processed,assembled and tested,and the results were more consistent with the simulation.The decoupling method is simple and effective,easy to process,does not increase the antenna profile,and has the dual-polarized multi-port decoupling effect without affecting the antenna's own radiation characteristics,and has the feasibility of array expansion.Therefore,the dual-polarization MIMO antenna decoupling method based on sub-array-unit coupling cancellation provides a new idea for the realization of dual-polarized multi-port large array decoupling.2.Research on the decoupling method of broadband/close-spacing MIMO antennas based on sub-array-unit coupling cancellation.In order to meet the needs of 5G applications,broadband antenna arrays and close-spaced antenna arrays were further designed,and based on the above-mentioned new decoupling methods and principles,decoupling structure loading was designed to achieve decoupling between ports in broadband and close-spaced arrays.Mainly analyze the loading effect of three new decoupling structures,and their respective corresponding to the heteropolar coupling in the subarray,the heteropolar coupling between the adjacent ports of the subarray,and the heteropolar coupling of the non-adjacent ports between the subarrays.The decoupling mechanism finally realizes broadband decoupling that can cover the n78 frequency band when the array element spacing is less than 0.41 spatial wavelengths,and the isolation between all ports can be increased to more than 20 d B,that is,the broadband close spacing is practically improved.Port isolation of dual-polarized arrays.Finally,the proposed broadband antenna array loaded with decoupling structure was processed and tested,and good performance was obtained.It was verified that the proposed new decoupling method based on the principle of sub-array-unit coupling energy cancellation has good broadband and short-distance expansion.performance.3.Research on the decoupling method of 5G-oriented MIMO phased array antenna.In order to meet the needs of 5G phased array wide-angle scanning,a 4×4 broadband phased array antenna with one drive and two modes was designed,and the new decoupling method proposed above was extended to the array to achieve wide-range beam scanning performance.On the basis of the above decoupling method,in response to the expansion needs of large-scale arrays,a symmetric decoupling structure in the sub-array is proposed,and the array is expanded and loaded in the horizontal and vertical dimensions,and a 4×4 broadband high isolation is designed.Antenna phased array.The proposed decoupling structure improves the isolation performance between multiple ports in the array,achieves ±65° wide-range beam scanning in the matched frequency band,and greatly improves the active return loss performance of each port,especially at large angles.Under the excitation of the scanning feed,the active performance of the port is optimized and the array efficiency is improved. |
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