| With the advent of 5G information,people have more requirements on the performance of mobile terminal devices,and the space left for antenna design in the terminal has been increasingly improved.The MIMO(multiple-input multiple-output)antenna technology has attracted extensive attention in the communication field due to its advantages of enhancing the channel capacity of the system and reducing the negative impact of multi-path interference.Therefore,how to realize the decoupling of multi-band antenna array and the miniaturization of antenna design in the limited smart phone has become a very challenging topic nowadays.In recent years,China has put forward the application in 5G mobile terminals of several Sub-6 GHz frequency LTE42(3.4GHz to 3.6GHz)/(3.6 GHz to 3.8GHz)43/46(5.15GHz to 5.925GHz)/(4.8GHz to 5GHz),and 5.8GHz centered frequency of WLAN band(5.725GHz to 5.875GHz),in this paper,based on the above several frequency design several applications in mobile terminal MIMO antenna,here are the paper's main work and research results are as follows:Firstly,a ten-unit multifrequency MIMO antenna is designed for Sub-6GHz,the antenna unit form for the slot antenna,in the middle of the original "U" type slot antenna change add troubles to the "E" type antenna,high frequency matching can be improved,and after adding the junk "E" type antenna top add open side to introduce a quarter wavelength low-frequency resonance point;The antenna is fed through the coupling of "L" branch,which greatly improves the impedance matching characteristics of the antenna.Will through the space diversity and polarization diversity antenna array technology group,reducing the coupling effect between the antenna,through comparing different set of array form,eventually optimize the bandwidth of the antenna to 2.92 to 3.96GHz and 5.56 to 5.94GHz(10dB),covering LTE42/43 Sub-6GHz band and the WLAN band centered around 5.8GHz frequency,degree of isolation between antennas above 10dB,ECC is less than 0.1,meets the design requirements of the terminal antenna.Secondly,a miniaturized 16-unit MIMO antenna is designed for 3.5GHz frequency band.The antenna element is a slot antenna.The matching characteristics of the antenna are improved through "L" type branch coupling feed.The size of the optimized unit antenna is finally(3.5GHz wavelength),and the antenna is composed of 16 unit MIMO antenna.The total size of the two adjacent antennas with spacing is 0.19.By adding the mutual coupling between the "L" type feeder lines of adjacent units and the improved inductance unit antenna,the 16-unit antenna after the final optimization can meet the bandwidth of 3.4GHz to3.6GHz(-6dB),the isolation degree between the antennas is more than 10dB,and the ECC of the antenna array is less than 0.25,which can be applied to the design of mobile terminal antenna.Thirdly,a broadband high isolation two-unit MIMO antenna is designed for mobile terminal equipment,the antenna unit form for the slot antenna,through a small gap in the quarter wave of an inverted "L",and adding in the low frequency to introduce a new resonant mode,so as to realize the direction of the antenna to the low frequency deviation,add a new low frequency spectrum bandwidth,the bandwidth of the antenna is 3.36GHz to 6.93GHz(6dB).It can cover the sub-6GHz band of LTE43 and LTE46,4.8GHz to 5GHz and the WLAN band with 5.8GHz as the center frequency point.Due to the particularity of antenna structure,the isolation between two adjacent input and output ports is improved.An ideal spatial diversity is achieved through antenna array,and the final isolation between antennas is greater than 20dB and ECC is less than 0.03,which meets the design requirements of terminal antenna. |
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