Design Of Compact Microstrip Antenna Arrays With Low Mutual Coupling

In recent years the needs of wireless communication increase very fast,especially the demand for high frequency and high speed data communication.Multiple-input multiple-output?MIMO?technology can improve channel capacity and transmission reliability without the increase in transmission bandwidth and transmitting power,which makes the multi-port antenna array attract increasing research and applications.Nowadays,many technologies and applications have been developed to be allocated in different operation frequencies.The devices which can be applied and operated in several frequency operations in same time are needed,such as an antennas array with multiple bands.In the research fields of antenna engineering,the microstrip patch antennas are widely used because of their several advantages.In its development,recently microstrip patch antennas have been approached from antenna characteristics optimized to antenna array characteristics.This research proposes compact microstrip antenna array designs with low mutual coupling,which can be applied and operated in such cases.Firstly,the thesis introduces the background of the research,and then summarizes the progress in the research of decoupling microstrip antenna array in recent years.Furthermore,the basic theory of antennas and the theory and design techniques of microstrip antenna are briefly explained.Then,the neutralization technique is firstly used to reduce the mutual coupling between the two antenna elements of microstrip array.The working mechanism of neutralization line is analyzed,and the neutralization lines are used in the proposed single-frequency and dual-frequency microstrip antenna arrays.By varying the related design parameters of the neutralization line,the S₁₂ of the array at the resonant frequency is reduced obviously.It means that the mutual coupling of the array has been suppressed effectively.Finally,the function of the U-shaped resonators in mutual coupling suppression of the microstrip antenna array is studied.By adjusting the dimensions of the U-shaped resonator,good mutual coupling reduction can be achieved at the resonant frequency of the array.By using the combination of the resonators with different sizes,the mutual coupling of the dual-frequency array can be suppressed at the two resonant frequencies.The neutralization line and resonator techniques are applied separately in several designs,including the single-frequency and dual-frequency microstrip antenna arrays.Details of the designs are presented and the simulation results are discussed to analyze the radiating characteristics of the array.The results show that by using the neutralization line and resonator techniques,the microstrip antenna array which generally has high mutual coupling characteristics can be successfully reduced to low mutual coupling.