Research On New Technology Of Transmit-Receive Isolation For Ultrawideband Antenna

With the rapid development of radar detection technology and MIMO technology,the demand for increasing transmitter power and receiver sensitivity is increasing,which causes the problem of mutual coupling of electromagnetic waves.In addition,ultra-wideband technology is also being integrated into radar,communication and other fields.How to improve the isolation between transmitting and receiving antennas(especially ultra-wideband transmitting and receiving antennas)has become an urgent problem.This article first analyzes the mutual coupling mechanism and source of mutual antennas,and then studies the methods to improve the isolation of the transmitting and receiving antennas.The main research object is spatial isolation.First analyze the suppression principle of antenna coupling energy by these methods,and then combine these methods to develop a new technology for improving isolation of transmitting and receiving antennas.Start with a narrow-band antenna and then promote it to a wide-band antenna.The coupling path between the transmitting and receiving antennas is loaded with electromagnetic metamaterials,metal isolation plates and absorbing materials to improve the isolation of the antenna.Finally,the effectiveness of the new technology is verified by simulation or experiment.The main content of the article is as follows:(1)An F-shaped hybrid isolator is designed for narrow-band antennas that are far apart.It consists of an F-shaped metal isolation plate and an EBG array.The metal isolation plate is used to isolate space waves and make a phase compensation for the antenna.The EBG array is used to suppress surface waves.Simulation results show that the isolation at the center frequency of the antenna is improved by 44.5d B,which greatly reduces the mutual coupling between the antennas.At the same time,the beam splitting problem caused by the long ground plate was corrected,and the main radiation direction of the antenna E-plane pattern was adjusted from-50 ° to-11 °,and the maximum radiation gains of the E and H planes were 8.12 d B and 7.32 d B.Compared with the 6.92 d B of a single antenna,the gain of the antenna is also improved after loading the F-shaped hybrid isolator.(2)A polarization isolator is designed for narrow band antennas that are close to each other.A polarization converter is loaded between linearly polarized antennas arranged along the polarization direction.The polarization isolator rotates the direction of the magnetic field,changes the direction of the surface current transmitted,and makes it perpendicular to the polarization direction,thereby improving the isolation of the antenna.Simulation results show that the isolation at the center frequency of the antenna is improved by 16.2d B,and the addition of a polarizer has no effect on the antenna's main polarizied radiation pattern and gain.(3)For the ultra-wideband circularly polarized transmitting and receiving antennas,an integrated transmitting and receiving isolation device was designed.It consists of metal isolation plate,multi-band cascaded EBG array,Miniaturized ultra-wideband metamaterial absorber loaded with lumped resistance,and absorbing paint.Isolation effect covering 6GHz ? 18 GHz ultra-wideband is achieved.Simulation results show that the isolation in all frequency bands is improved.The processed samples were tested,and the isolation test results generally matched the simulation.However,since the S21 level in the high-frequency band of 14 GHz to 18 GHz is too low and it is affected by environmental noise too much,accurate results cannot be measured.Comparing the antenna array loaded with the integrated transmitting and receiving isolation device with the antenna array loaded with traditional absorbing materials,the antenna's horizontal polarization and vertical polarization patterns did not change significantly,and the isolation increased by an average of2.43 d B(6GHz?14GHz).Comparing the antenna array loaded with the integrated transmitting and receiving isolation device with the antenna array without measures,the average isolation increased by 7.66 d B(6GHz?14GHz).