Design Of Microstrip Reflectarray Antenna Based On Multiple Resonant Elements

As a commonly used high-gain antenna,the microstrip reflectarray antenna plays a very important role in modern communication systems.It is a combination of traditional parabolic antenna and array antenna.As a result,it has the advantages of these two antennas,such as low profile,light weight,small size,low cost,high directivity,simple structure,and low design difficulty.It is precisely because of these advantages that microstrip reflectarray antennas are widely used in many fields and are increasingly being valued by people.The microstrip reflectarray antenna is composed of a feed antenna and a flat reflect array.The spatial phase delay from the feed antenna to the reflecting surface of each unit is different.In order to realize the highly directional radiation beam in the specified direction,it is necessary to adjust the structure of the unit to compensate for the phase difference at different positions.However,the traditional microstrip reflection unit has large size,narrow bandwidth and small range of phase shift.In this paper,a novel type of multi-resonant microstrip reflection element is designed based on the Archimedes spiral structure,which improves the phase compensation performance of the unit and broadens the gain bandwidth of the antenna.The main work is composed of the following two parts:(1)Design of microstrip reflectarray antenna based on Archimedes spiral multi-resonant elementThe basic reflection unit consists of four rotationally symmetrical Archimedes spiral elements.A 10×10 microstrip reflectarray antenna is proposed based on the element.The unit period is 0.39?₀,and the dimension of the reflection surface is 200 mm×200 mm.The simulation results show that at the operating frequency of 5.8 GHz,the antenna gain is 18.7 dBi,and the1.5-dB gain bandwidth is 22.1%(5.56-6.84 GHz).The phase shift compensation characteristics of the element are improved by loading the ring element in the center of the spiral.Under the same aperture size,the measured results show that the antenna gain is increased to 18.9 dBi,the 1.5-dB and 3-dB gain bandwidth are 23.1%(5.50-6.84 GHz)and 31.4%(5.31-7.13 GHz)respectively.(2)Design of microstrip reflectarray antenna based on double Archimedes spiral rings elementIn view of the idea of multi-resonance,a 11×11 microstrip reflectarray antenna is designed using double Archimedes spiral rings as the reflection unit.The element size is reduced to 0.348?₀,which realize miniaturization.And the aperture size of the reflection surface is 198 mm×198 mm.The simulation results show that the antenna gain is 19.1 dBi,the side lobe level is lower than-15.4 dB,the cross polarization is less than-29.7 dB,and the 3-dB gain bandwidth is 34%(5.30-7.27 GHz).