Research On Circularly Polarized Antennas Of Satellite Navigation System

The circularly polarized antennas of satellite navigation system are studied in this thesis based on the research projects.The main contents are as follows:Firstly,the related concepts involved in the thesis are introduced,the current status and existing problems of research are discussed,the background and significance of circular polarized antennas of satellite navigation systems are elaborated,the basic theories and methods used in the thesis are also discussed.Secondly,the circularly polarized antennas of satellite navigation system are studied.The specific research work contains three parts:1.Research on miniaturized GPS missile-borne navigation circularly polarized conformal arrayThe first part of the thesis is the research on miniaturized GPS missile-borne navigation circularly polarized conformal array.The specific research work includes the following two sections:1)In order to meet the miniaturization performance requirements of circularly polarized antennas of missile-borne navigation systems,doubly-fed square-shaped circular microstrip patches are used as array elements to study circularly polarized conformal arrays of missile-borne navigation.In this thesis,the coupling feeding structure is used to improve the impedance matching characteristics of the array unit,and the surface current path of the square-ring patch is increased by the recessed structure,thereby the miniaturization of the antenna is achieved.The antenna unit is processed and tested in the dissertation.The designed miniaturized GPS missile-borne navigation circularly polarized conformal array unit has an impedance bandwidth(VSWR?2.0)of 1.280GHz?1.720GHz,an axial ratio bandwidth(AR?3d B)of 1.572GHz?1.589GHz,and a maximum radiation direction gain of 1.3d Bic.The electrical dimension of the array unit is only0.19₀?×0.19₀?×0.004₀?(excluding floor and power divider),which meets the arraying requirements of the miniaturized GPS missile-borne navigation circularly polarized conformal array.2)Design of miniaturized GPS missile-borne navigation circularly polarized conformal arrayOn the basis that the performance of the array unit meets the requirements of the array,the array units are arrayed and conformal.Then the array is simulated and analyzed under the condition of loading the missile-borne.The simulated results show that the designed miniaturized GPS missile-borne navigation circularly polarized conformal array satisfies VSWR?2.0 in the frequency range of 1.220 GHz to 1.720 GHz,and AR?3 d B in the frequency range of 1.572 GHz to 1.589 GHz.The direction(?=90°,?=0°?360°)satisfies Gain?-2.9d Bic,and the out-of-roundness is 0.3d B,which meets the requirements of the missile-borne navigation system.2.Research on Beidou&GPS navigation laminated dual-frequency circularly polarized microstrip antennaIn the first part of the thesis,the miniaturized circularly polarized antenna of the missile-borne navigation system is studied,but the antenna works in a single frequency band.Considering compatibility and reliability issues with multiple navigation systems,Beidou&GPS navigation laminated dual-frequency circularly polarized microstrip antenna is studied in the second part of the thesis.The specific research contents are as follows:According to the dual band and miniaturization requirements of satellite navigation systems for circularly polarized antennas,a laminated microstrip antenna structure is selected to achieve dual frequency bands.U-shaped slots are used to generate perturbations to the current distribution of the patch to achieve circularly polarized radiation.Miniaturization of the antenna is achieved through the ring structure patch and the introduction of the RIS structure.The antenna is processed and tested,and the measured results show that the designed Beidou&GPS navigation laminated dual-frequency circularly polarized microstrip antenna meets VSWR?2.0 and AR?3d B at two frequencies:BDS-B3(1.268GHz)and GPS-L1(1.575GHz),the impedance matching characteristics and circular polarization performance are good,the size of the antenna is 77.5×77.5×6.2(mm³),which meets the miniaturization requirements of circular polarization antennas of satellite navigation system.3.Research on circularly polarized cross dipole antenna with wide bandwidth and axial ratio beamwidthThe second part of the thesis studies the miniaturization and dual-band of circularly polarized antennas for satellite navigation systems,but it can not meet the requirements of working frequency bands of multiple satellite navigation systems at the same time and wide AR beamwidth requirements.Therefore,in the third part of the thesis,a circularly polarized cross dipole antenna with wide bandwidth and AR beamwidth is developed.The specific research contents are as follows:In response to the satellite navigation system's application requirements for the circularly polarized antenna's wide frequency band and wide AR beamwidth,a curved arm and parasitic structure are adopted to widen the AR beamwidth of the cross dipole.The working bandwidth of the antenna is broadened by the slot coupling feed structure and Wilkinson power-division feed network.The antenna is processed and tested,and the results show that the designed circularly polarized cross dipole antenna with wide bandwidth and axial ratio beamwidth has an impedance bandwidth(VSWR?2.0)of1.20GHz?2.00GHz and an AR bandwidth(AR?3d B)of 1.22GHz?1.98GHz,the 3d B power beamwidth and 3d B AR beamwidth reach 155°and 210°,respectively,which meets the wide band and wide beamwidth application requirements of satellite navigation system.Finally,the main results of the thesis are summarized,and the problems that need further research are pointed out.