| Since the late-20thcentury,wireless communication service has evolved from the first generation to fourth generation,during this period,some complex services,including WLAN,WiMAX,has been applied into communication services.In order to meet this growing demand,improving the speed of transmission has become the main trend of the development of the recent communication field and introduced a new technology,Multiple Input Multiple Output?MIMO?technique.MIMO technique can achieve linearly-increased high-speed without using extra bandwidth and power.However,improving isolation between antennas configured in small mobile devices brings about serious problem to the antenna designers.Based on the background of wireless communication and the development of mobile terminal antenna,this paper introduces the basic principle of the coupling between mobile MIMO antenna units,and describes the influence of MIMO antenna unit correlation on system performance.According to the characteristics of the antenna spatial diversity technique,the performance of the MIMO antenna is evaluated based on the impedance and the S parameter?scattering parameter?matrix.This method is based on the S parameter formula,considering the more comprehensive factors.It can be applied not only to the engineering design of mobile terminal antenna,but also to calculate the envelope correlation coefficient of the simulation model in the simulation design.Based on the design principle of PIFA antenna and the decoupling status of WLAN compact and low coupling MIMO antenna system,a WLAN compact and low coupling mobile antenna system is proposed.In the range of all WLAN frequency bands,the return loss bandwidth completely covers the 2.4GHz,5.2GHz and WLAN5.8GHz frequency bands,and the antenna has good directional omnidirectional property.In this paper,a high isolation requirement is realized by using a kind of defective grounding structure.The size of the antenna is only 25mm x 12.5mm x 8mm,which is suitable for installation in mobile terminal equipment and the performance meets the practical application requirements. |
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