| Wireless communication technology has made tremendous development during the modern days.The demand of consumers is growing for intelligent products with multiple wireless communication functions.Intelligent terminal products continue to develop towards miniaturization,multi-function and wearable.The space available for antenna is becoming narrow and crowding.In addition,traditional communication technology and increasingly tense spectrum resources are difficult to meet the needs of high channel capacity and high-speed communication.MIMO(Multiple-Input Multiple-Output)technology can greatly improve the communication rate and wireless channel capacity without requiring increases in transmission power and spectrum.Therefore,MIMO technology has drew the attentions of the domestic and foreign scholars.It is widely regarded as one of the core technologies of the fourth and fifth generation mobile communication.MIMO antenna,as a key device of intelligent terminal receiver and transmitter,has also attracted much attention.Based on the two problems mentioned above,this dissertation focuses on miniaturization,multi-band,multi-antenna and other related technologies.This thesis mainly includes the following contents:1.Based on the working principle of monopole antenna,a miniaturized hexa-band monopole antenna is proposed by using multi-branch loading method.By reasonable combination of three different shape and size branches,the reflection coefficient of the antenna from 1.43 GHz to 2.23 GHz and from 2.29 GHz to 2.55 GHz are less than-10 dB.It can be applied to GPS,DCS1800,PCS1900,UMTS2100,WLAN 2.4GHz and Bluetooth communication band.2.Based on the working principle of microstrip patch antenna,a compact quad-band microstrip antenna is proposed by feeding in diagonal position coaxially and loading two U-shaped slots of different sizes on the patch.The impedance matching of the antenna is adjusted by slotting in the grounding plate,so that the frequency band covered by the antenna are 1.88~1.92 GHz,2.41~2.45 GHz,3.47~3.57 GHz,5.19~5.30 GHz.It can be applied to NB-IoT,WiMAX,WLAN(802.11n)communication band.3.Based on the decoupling principle of floor branche and slot,a tri-band four elements MIMO antenna is proposed,combining the multi-resonant mode characteristics of monopole antenna.A Y-shaped structure with a slot in the middle is designed,which combines the traditional decoupling methods of floor branch and floor slot,and reduces the coupling caused by surface current and space wave of metal grounding plate simultaneously.Combining the structure with four rectangular slots,the four elements MIMO antenna is decoupled.Using these two methods,the coupling between different antenna elements is suppressed,so that the isolation of the antenna in the band when exteed 2.4GHz is higher than 15 dB.In order to verify the actual performance of the designed antenna,the three antennas are fabricated and measured.The measured results are in alignment almost with the simulation results,which meets the communication requirements of miniaturized intelligent terminal equipment. |
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