Research On Antenna Pattern Based On Theory Of Characteristic Mode

With the advent of the information age,the requirements of equipment for communication quality are gradually increasing.In order to improve the data transmission rate,multiple in multiple out(MIMO)antenna mobile phones put forward high requirements for low correlation multiple antennas.The characteristic mode theory has a clear physical concept.Starting from the working mechanism of the antenna and according to the independent characteristics of each characteristic mode,the excitation of the specified radiation far field can be realized.In this dissertation,a four-port antenna system at 2.4 GHz is designed exciting quasiomnidirectional total patterns for the first time by analyzing the characteristic mode of loading frame on ultra-thin metal substrate.On the two main planes,the gain variation is only 3.4 d B and 3.6 d B.The isolation between antennas is more than 15 d B and the correlation is less than0.01.Maintain a complete ground level and a small clearance of 2mm.Then an eight port antenna system is designed by using the clearance between the metal substrate and the frame.The center frequency of the eight antenna units is 2.4 GHz,the antenna bandwidth is 90 MHz,and the correlation between antennas remains below 0.07.The antenna system is fabricated,and the measurement results are in good agreement with the simulation results.In this dissertation,we also research the pattern synthesis of single antenna based on the characteristic mode theory,and solves the feeding information of antenna through the target pattern.Firstly,according to the calculation formula of the correlation coefficient between the far-field of the two antennas,the calculation formula of the mode weight is derived,and the mode weight coefficient of the characteristic mode far-field in the total far-field is obtained.Then the compressed sensing algorithm is used to optimize the antenna feed solution results,and a complete set of pattern optimization algorithm is obtained.The algorithm is applied to the ship three-dimensional antenna structure,and the correlation coefficient between the synthesized pattern and the target pattern reaches 0.71,which shows that they have high correlation,and the algorithm has application potential.Based on the theory of characteristic mode,this dissertation studies the pattern of mobile phone antenna and ship antenna,and realizes the construction of full circle pattern of mobile phone MIMO antenna and the pattern synthesis of low elevation omnidirectional ship antenna respectively.Despite the large volume difference between them,the characteristic mode theory is still a powerful tool to study the antenna pattern.