| As IEEE announces MIMO as one of the key technologies for4G, a variety of research about MIMO has become a hotspot. To date, multi-antenna technology in MIMO transmitter and receiver has become the biggest bottleneck of the business. At present, the base station side can be very easy to implement low correlation by separating the antenna elements in space. However, in the mobile terminal restricted by the antenna size, how to place more than one antenna in its limited space and maintain a low correlation has become one of the hotspots. In addition, more and more new communication standards emerging, which require terminal antenna to meet the multiple bands or cover a wide frequency band. Therefore, the study about the MIMO terminal antenna broadband/multi-band applications and improvement of isolation between the antenna elements has a very important significance.Firstly, this article designs a dual-band compact MIMO terminal antenna. The antenna consists of two "F" shaped monopole antenna elements, a "T" shaped extension of the ground. The proposed antenna used the FR4substrate with a thickness of1.6mm, which has a compact volume of99X60mm2. Testing of the antenna operating bandwidth covering the1700-2900MHz and5050-5400MHz with better than-14dB of isolation.The antenna radiation pattern display can provide pattern diversity. The diversity gain is calculated based on correlation coefficient and mean effective gain, and the value is9.43dB.Secondly, the author designs a wideband compact MIMO terminal antenna. The antenna composed of two "G" shaped monopole placed by "back to back". The proposed antenna extends the ground in order to get a wider bandwidth and lower coupling method with introduction of two inverted "L" shape branches and a "T" shaped branches. The antenna has a compact volume of99×55mm2, which used the FR4substrate with a thickness of1.6mm. Test results show that the antenna covers1700-2900MHz wideband and isolation better than-17dB. The calculation of the correlation coefficient and mean effective gain of the antenna shows it can provide9.68dB of pattern diversity gain.The final design is a high isolation MIMO antenna. The antenna lead into a mushroom-type EBG structure to reduce the coupling between the antenna elements. The antenna has a compact volume of99X55mm2, which used the FR4substrate with a thickness of1.6mm. The antenna unit consists of two "G" monopole. The middle of the two monopoles arranged in a certain number of mushroom-EBG strcture. Different number and arrangement of the EBG strcture is analyzed. The simulation results show that the antenna bandwidth covering the2400-2830MHz, WLAN and WiMAX bands. The antenna has better than-21dB of isolation, such a low mutual coupling to ensure its superior MIMO performance. |
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