Design And Implementation Of The High Gain And Low Sidelobe Circularly Polarized Microstrip Array Antenna

In 1970 s,due to the development of microwave integrated technology and the urgent requirement of space technology for low profile antenna,microstrip antenna has attracted the attention of more and more researchers.Microstrip antenna has many merits,such as small size,light weight,thin profile,easy to be conformal to carrier surface,flexible feed,easy to achieve functions such as circular polarization and dual band,can be integrated with active circuits,suitable for large-scale production and low cost.It has been widely used in military and civil fields.However,microstrip antenna also has a few drawbacks such as narrow band,large loss,small power capacity,etc.Based on the actual needs,a high gain and low sidelobe circularly polarized microstrip array antenna is designed in this paper.The main contents of this paper are as follow:1.The basic theory and technology of microstrip antenna are studied,such as the definition,type and structure of microstrip antenna,operation principle,analysis methods and basic parameters,feeding modes of microstrip antenna element,radiation characteristics and feeding modes of microstrip array antenna.It provides theoretical basis for the design of the antenna.2.In the aspect of the microstrip antenna unit design,a single rectangular microstrip with adjustable chamfers is used as an antenna unit,and single feed method is used to realize circular polarization.Thus there are a lot of benefits such as easy to adjust the impedance and axis ratio,good for reducing the complexity of the feed network,good for reducing the feed loss and improving the gain of the antenna.The Ansoft HFSS software is used to simulate and optimize the design of microstrip antenna.The simulation results show that the polarization characteristics and the impedance matching characteristics of the microstrip antenna unit are good.3.In the aspect of the microstrip antenna array design,array antenna is composed of eight antenna units,in which two sub arrays are symmetrically placed.The two sub arrays are fed in parallel by two signals of the opposite phase with the same amplitude,that is,the phase difference of the two signals is 180 degrees,which guarantees the maximum antenna gain.In the four-unit sub array,4 antenna units are fed in parallel by a continuous rotating structure,that is,the phase difference of each radiating unit is 90 degrees,and the broadband characteristic of the antenna is extended.The Ansoft HFSS software is used to simulate and optimize the design of the antenna array,which is based on the spacing of antenna unit in the array,side lobe,circularly polarized array,feed network and the whole antenna array.The simulation results show that the high gain and low sidelobe target of the array antenna are satisfied.4.In the aspect of the antenna manufacturing and testing,the circularly polarized microstrip array antenna is machined and assembled,and the electrical performance of the antenna array is tested.The experimental results show that the array antenna has the impedance characteristics of wide band,good circular polarization,high gain and low sidelobe.The measurement results are in agreement with the simulation result,which shows that the design method of the array antenna is correct and has certain application value.