Research And Design Of 5G Filtering Antenna And MIMO Filtering Array

At the time of 4G development in the ascendant,the fifth-generation mobile communication（5G）has entered the fast lane of development,due to its greater information carrying capacity,faster transmission rate and more terminal support number.As a new generation of mobile communication technology,5G puts forward several higher requirements for RF front-end devices.First,the limited design area and the multiplied number of devices require each device to be smaller and more integrated.Second,the complex application scenarios and higher power requirements require the RF system has good robustness.Third,the wide application of multiple input multiple output technology（MIMO）requires low correlation between antennas.Based on these requirements,this thesis focuses on studying filter antenna that is the excellent candidate of 5G antenna.The filter antenna is an integrated design of antenna and filter.It has both function of radiating signal energy and filtering out unwanted signals.Using filtering antenna can not only reduce the overall size of the RF front-end,but also avoid the loss caused by cascade matching network,which is useful for improving the RF front-end performance and efficiency,and have a good prospect.According to the above requirements,this thesis has designed several filter antennas as solutions:Firstly,a planar quasi-Yagi filter antenna with integrated design is proposed.It is based on a parallel double-sided strip line structure.By improving the driver dipole,introducing a forward and backward parasitic structure and embedding a small band-stop structure,it achieves a good filter response.Meanwhile,it also has a wide working frequency band and an ultra-wide stop band.The thesis analyzes the design steps and principles of the filter antenna.To confirm the validity of the numerical simulation,a prototype was fabricated and measured.The measured results are 78.2%of 10-d B impedance bandwidth,4.4 d Bi in-band average gain,20.2 d B out-of-band suppression level,and upper bandedge of stopband is improved to up 3.1 f₀.Secondly,introducing an absorptive filtering antenna protects the power amplifier away from the instability effects in high-power applications.The absorptive filtering antenna based on the stacked patch.The out-of-band signal energy will be absorbed by this antenna,which prevent the energy reflect to the source to cause self-excited oscillation.The function of absoption is realized by the band-stop absorption branch that constructed by the defected ground structure.Therefore,the signal in the working band flows to the antenna and radiates,and the signal outside the working band is dissipated in the resistance.A unique"all-pass characteristic"is generated due to the great complementarity of the transfer function.The proposed absorptive filter antenna has a radiation bandwidth of 24%（3.3-4.2 GHz）,a reflection-less bandwidth of 70%,and the average gain is 7.9 d Bi.After that,a four-element MIMO absorptive filtering antenna array has been introduced for MIMO application.All the elements are orthogonal arrangement on the array.It not only realizes the absorptive filtering function in each antenna,but also the low correlation between elements.The isolation of prototype has been measured as more than 24 d B over whole spectrum,which is more than 25 d B in working frequency band.The envelope correlation coefficient（ECC）is less than 2×10^-4.In addition,a 4×2MIMO absorption filtering antenna array is proposed,in which two sets of elements work in the N77 frequency band and the N79 frequency band respectively.By comparing with the ordinary stacked patch array,the different frequency band decoupling advantage of the proposed absorptive filtering antenna element has been verified.Adopting this element,in multi-frequency band array,the isolations between the different frequency elements are improved by at least 8.3 d Bi.