| When the transceiver shares the same antenna,coupling will inevitably occur between the two signals.The existence of coupling not only reduces the antenna efficiency,but also increases the difficulty of processing the received signal.Moreover,the isolation of the two signals is more important for systems that transmit and receive signal in the same frequency band.A circulator is usually used to achieve good isolation for systems that share the same antenna for transmiting and receiving signal.However,it will increase the design complexity and cost of the system,and bring a certain amount of loss.For systems that use separate antennas for transmiting and receiving signal,called dual-antenna systems,the higher isolation is achieved by designing a decoupling structure.Therefore,the research on the decoupling technology of the dual-antenna system will be studied in depth in this paper.Furthermore,the different decoupling structures are proposed.The main work and contributions of this paper are as follows:(1)Two broadband decoupling structures are proposed and applied in the microstrip monopole antenna.The focus is on solving the mutual coupling problem between adjacent antennas in the ultra-wideband technology.The two proposed decoupling structures can achieve good decoupling effects in the range of 3.1 GHz-10.6 GHz,and the isolation can reach more than 20 d B.The first proposed decoupling structure is implemented in the rectangular monopole antenna with truncated corners.Ultra-wideband decoupling properties is obtained by loading T-shaped stub on the ground and a set of electromagnetic band gap structures between adjacent monopoles.Coupling effect.The proposed second decoupling structure is applied to a circular monopole antenna.The decoupling structure achieves the ultra-wideband decoupling effect by loading graded T-shaped stub on the ground.(2)Two miniaturized,high isolation wideband decoupling structures are designed for microstrip patch antennas.For the first decoupling structure,wideband decoupling is achieved by combining a half-wavelength defect ground stucture and a metal vertical baffle.As a result,the working bandwidth of antenna is 1.65GHz(5.23GHz-6.87GHz),and the isolation is greater than 20 d B.The second decoupling structure is designed by using the orthogonality of the antenna polarization and combining multiple half-wavelength defect ground stucture to further improve the performance of wideband decoupling.The measured bandwidth is 1.53GHz(4.96GHz-6.49GHz)),the isolation is in the range of 25.2d B-49.6d B.(3)Two new wideband decoupling structures are designed based on half-wavelength resonators.The microstrip patch antenna is implemented with two dielectric substrates,in which the radiating patch is located on the bottom layer of the higher substrate,and the decoupling structure is placed on the top layer of the lower substrate.Thus,more design space can be provided for the decoupling structure.The first proposed decoupling structure is composed of the microstrip line located in the direction of the antenna polarization in series with seven half-wavelength microstrip resonators with different intervals and unequal widths,which is located in the orthogonal direction of the antenna polarization.The starting point of the design is half-wavelength resonators can bind the coupling current between the adjacent antennas,thereby improving the isolation between adjacent antennas.The working frequency of the antenna is in the range of 6.18GHz-6.89 GHz,the relative bandwidth is 10.9%,and the isolation is 22.7d B-46.3d B.The second decoupling structure is achieved by a microstrip line located in the orthogonal direction of the antenna polarization in series with five S-shaped microstrip resonators with different intervals and unequal widths located in the direction of the antenna polarization.The working bandwidth is 6.01GHz-6.79 GHz,the relative bandwidth is12.2%,and the isolation is 21.6d B-42.9d B. |
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