Optimization Research On Massive And Broadband Microstrip Antennas

The antenna is the carrier of sending and receiving signals for wireless communication systems.The research on antennas with high performance will directly result in whether the new generation wireless communication technology can achieve some unique features,such as massive capacity,ubiquitous connectivity,super energy efficiency,high peak data rate,and full applications,etc.In massive multiple-input and multiple-output(MIMO)systems,deploying an antenna array at the base station can obtain the array gain,diversity gain,and multiplexing gain,then the transmission reliability spectrum efficiency can be effectively improved.However,the large number of antennas causes some technical problems such as sharply increased power consumption and high computational complexity.Thus,how to effectively improve energy efficiency while ensuring spectrum efficiency is one of the key issues for future wireless communication technologies.Besides,with the further enrichment of application scenarios for the new generation wireless communication systems,broadband antennas designed for multiple wireless communication standards and multiple wireless communication scenarios have been rapidly developed to reduce the restriction of the number of antennas on the performance of the entire communication systems.As a result,the realization of the broadband antenna is another vital issue for future wireless communication technologies.This thesis intends to fully explore the potential advantages of both antenna forms and antenna structures.Based on two prerequisites of the ideal point-source antenna and non-ideal point-source antenna,this thesis studies the optimization techniques on massive and broadband microstrip antennas by focusing on the system's spectrum efficiency,energy efficiency,bandwidth,and radiation characteristics.The main work of the thesis includes:(1)In terms of a uniform array of ideal point-source,a joint optimization method of security and resource is proposed for massive antennas hybrid beamforming.Considering that the Massive MIMO systems exit some problems such as large power resource consumption and poor security and confidentiality performance,an equivalent secure channel matrix is defined,and the secure energy efficiency(SEE)and secure achievable rate(SAR)is optimized for multi-user Massive MIMO eavesdropping systems,which is the non-convex optimization problem.The continuous relaxation algorithm is used to convert the non-convex problem into a convex problem.And a SEE-SAR joint optimization algorithm based on the successive convex approximation is proposed.The initial optimized variable of the analog precoding matrix can be solved by the phase quantization method.The simulation results show that the proposed algorithm effectively improves the SEE-SAR tradeoff range,and the SAR keeps around 28-40b/s/Hz when the SEE is 1.9-2.4bit/Joule/Hz.(2)In terms of the non-uniform array of ideal point-source,the optimization methods of the geometric structures of massive arrays based on group intelligence algorithm and ensemble learning are proposed,respectively.The geometric structures of the antenna array can affect beamforming,which further affects the system's spectrum efficiency and energy efficiency.On one hand,to minimize the peak side lobe level(PSLL),the geometric structures of the symmetrical sparse linear array are optimized using the hybrid group intelligence algorithm ICACO based on Imperial Competition Algorithm(ICA)and Ant Colony Optimization(ACO),in which the ICACO combines the advantages of the convergence speed of ICA and the global optimal search of ACO.The simulation results show that the PSLL optimized by the proposed ICACO is 0.27dB lower than ICA.On the other hand,the geometric structures of sparse concentric ring array(SCRA)are optimized by the proposed two-stage method based on ensemble learning K-BAG,which applies the weak learner based on K-Nearest Neighbor in Bootstrap aggregating(Bagging).The simulation results show that the simulated efficiency of the proposed method is about twice that of the improved genetic algorithm while the PSLL is basically unchanged.(3)In terms of non-ideal point-source antenna,the optimization methods for broadband planar inverted-F antenna(PIFA)with three resonant modes and the broadband circularly polarized antenna based on the symmetrical parasitic patch are proposed.As for linearly polarized PIFA,based on the original TM1/2,2 and TM3/2,o two resonant modes,a new TMRs resonant mode is excited by cutting a rectangular slot near the zero-electric field of the radiation patch.By adjusting the length of the rectangular slot and radiation patch,the three resonant modes are closed to each other to enhance the impedance bandwidth.The simulated and measured results show that the impedance bandwidth is expanded to 33.33%(5-7GHz),which is about 7.41 times larger than that of the traditional PIFA.As for circularly polarized microstrip antenna,through cutting a rectangular slot larger than the area of the radiation patch at the ground plate,and adjusting the size and position of the microstrip feeding line,two orthogonal resonant modes with equal amplitude and 90° phase difference can be generated at the ground plate to achieve a circularly polarized antenna.To expand the 3dB axial ratio bandwidth.two symmetrical rectangular parasitic patches are loaded on the left and right sides parallel to the central radiation patch,and a rectangular slot is cut on the lower right side of the central radiation patch.The simulated and measured results show that the 3dB axial ratio bandwidth is enhanced to 15.19%(28.77-33.5GHz)within the impedance bandwidth(35.97%,22.8-33.8GHz).(4)In terms of the non-uniform array of non-ideal point-source,an optimization method for higher gain and lower PSLL microstrip array using the broadband element with the dual-resonant modes is proposed.Firstly,the broadband microstrip array element with TM10 and TM02 dual-resonant modes is optimized.By cutting the symmetrical rectangular slots on the left and right sides of the radiation patch and loading a shorting pin at the center of the radiation patch to short the radiation patch and ground plate,the dual resonant modes are closed to each other to expand the impedance bandwidth.Furthermore,a series feed network is used to combine the array elements to achieve a linear array,and the PSLL of the proposed linear array can be effectively reduced by cutting symmetrical circular slots at each radiation patch of the array element.Then,the multi-parameter joint optimization algorithm based on ICA is proposed to optimize the array parameters,including the array element parameters and the feeding network parameters.The simulated and measured results show the peak gain and PSLL of the proposed array are 13dB and-19dB within the impedance bandwidth(6%,28.41-30.1 6GHz),respectively.