Research On Wideband Millimeter-wave MIMO Antennas

With the rapid development of the wireless communication industry,the low frequency spectrum resources are increasingly scarce,but the demand for high speed communication is increasing.Compared to the currently used 2G/3G/4G bands,millimeter-wave frequencies,which is up to 30-300 GHz and have a large number of continuous spectrum resources,can alleviate the current situation of spectrum congestion,provides the possibility for the realization of ultra-high speed wireless communication.Therefore,millimeter-wave technology will become one of the key technologies for the next generation of mobile communication technology(also known as 5G).The MIMO(multiple input multiple output)technology,which was introduced in the fourth generation of mobile communication,can effectively improve the capacity and reliability of the wireless communication system under the limited spectrum resource condition,therefore it is widely applied for many wireless communication systems.MIMO technology will certainly be used in the next generation of mobile communications with other communication technologies.This paper focuses on broadband design of millimeter wave antennas and it presents several MIMO antennas and multi cell antenna arrays with good performance.1.Two wideband planar T-shaped patch MIMO antennas are proposed.By introducing the metallic vias in the specific position on both sides of the transmission line,and adjusting the size of the feeding structure,a broadband antenna with a double resonance characteristic can be obtained.Based on this antenna,two stripe stubs are loaded into the feed structure,which can introduce a new resonance to broaden the bandwidth.At last,build on these two antenna elements,a two-port MIMO antenna and a four-port MIMO antenna are designed.The rhombic slots on the ground are used to reduce the mutual coupling of these MIMO antennas.2.Two MIMO antennas with end fire radiation characteristic are presented.Based on the structure of traditional monopole antenna,a coupling stub was introduced on the ground.By controlling the coupling between the monopole antenna and the stub,an antenna with a double resonance characteristic can be achieved.Based on this structure,two parasitic patches are placed in the end of the monopole antenna and the coupling stubs,which introduce a new resonance at the higher frequencies to broaden the bandwidth.According to the designed antenna element,two-port MIMO antennas with parallel placement and vertical placement are presented separately.The isolation of the MIMO antennas is improved by using ground slots and stripe stubs.3.Two high-gain planar patch antenna arrays are proposed.By loading rectangular patch on the side of the conventional patch antenna fed by substrate integrated waveguide(SIW)and controlling the size of the rectangular patch,the resonance of rectangular patch can be obtained and adjusted independently.In the feeding structure of substrate integrated waveguide,symmetrical metallic vias are introduced and after adjusting the position of metallic vias,impedance matching can be achieved and double resonance characteristic also can be obtained.By combining the two techniques of rectangular patch and metallic vias,the planar patch antenna element with a three resonance characteristic is completed.Then a four-port differential feed network is designed and combined with the antenna element,the four-port element antenna array is formed finally.