Design And Analysis Of Dual Circularly Polarized Microstrip Antenna

With the continuous development of satellite communication equipment in the direction of high integration and high communication efficiency,higher requirements have been put forward for the antenna.The dual circularly polarized microstrip antenna has a low profile,a light weight,and is easy to fabricate and realize circular polarization on the one hand;on the other hand,double circular polarization can improve spectrum utilization,reduce interference between adjacent channels,and improve communication quality.Therefore,dual circularly polarized microstrip antennas have become a research hotspot in the field of satellite communication.Firstly,the principle and analysis method of microstrip antenna are introduced.The conditions and realization methods of dual-circular polarized radiation for microstrip antenna are studied and summarized.The basic principles of linear array and planar array antenna are discussed.The phased array and its beam scanning principle are analyzed.Based on this,two dual-circular polarized microstrip patch antennas with laminated structure are designed.Both antennas are fed with dual feed points and use a broadband 3dB directional coupler to achieve dual-circular polarized radiation.The air medium reduces the Q value of the antenna,and the double layer patch increases the resonant point of the antenna,which improve the impedance characteristics of the antenna and widen the bandwidth of the antenna.To solve the problem of poor isolation between the two ports of the first dual circularly polarized microstrip antenna,a theoretical calculation and analysis was performed using the microwave network method.In order to verify the performance of the antenna,the proposed antenna is fabricated and measured.Secondly,a dual circularly polarized microstrip slot antenna was designed.By adjusting the slit width,the resonance frequency can be moved up and down.In the middle of the gap,metal branches are added to introduce perturbation,which causes the slot antenna to produce circularly polarized radiation.The two feed ports are symmetrically distributed on both sides of the symmetry centerline of the slot to achieve dual circular polarization.The lower half of the dual circularly polarized microstrip antenna was modified to a gradually changing slit structure,and the linearly polarized radiation was obtained by exciting the microstrip feed line at the bottom.Thus,a three-polarized microstrip slot antenna structure is proposed.Finally,a 4×4 cell array antenna was designed and applied to the SOTM(Satellite communication On-the-Move).In order to achieve beam coverage in the azimuth plane0~?360~?and elevation plane 0~?90~?,the array antenna uses mechanical scanning in the azimuth plane and one-dimensional phased array scanning in the elevation plane.Using high-isolation dual circularly polarized microstrip antennas as array elements,the array analysis,intercell mutual coupling analysis,low sidelobe design,direction graph analysis and phase scan analysis are carried out.