| Dual circularly polarized microstrip antennas have the advantages of low profile,resistance to multipath effects,easy to conform to the carrier surface,etc.,and are widely used in radio systems such as radar and communications.Aiming at the low-cost and miniaturized project requirements of a dome-shaped antenna array system with integrated X-band transceivers,this thesis uses microwave multilayer circuit technology to conduct a threedimensional integrated dual circularly polarized microstrip antenna array and feeding network.The main work and innovations are as follows:(1)Aiming at the demand for compact array of dome antennas,a design method of miniaturized directional coupler based on the T-shaped equivalent method is proposed.The size of the device is reduced by 40% compared with the traditional design.On this basis,a lowprofile dual circularly polarized antenna unit in the form of a microstrip patch is designed.The antenna realizes the connection between the circular radiating patch and the miniaturized coupler through metalized vias.The simulation results show that the gain of the antenna unit in the 10% bandwidth of the X-band is higher than 4.2d Bi,and the axial ratio is less than 1.7d B.Then,according to the sub-array-level layout scheme of the dome-shaped antenna array system,a semi-regular hexagonal 12-element sub-array based on a triangular grid arrangement was designed,with a gain higher than 14.2d Bi and an axial ratio lower than 2.17 d B.(2)Aiming at the requirement of double circular polarized sub-array double feeding network,a compact feeding network structure is proposed,which is based on the bent one-tothree and one-to-four power dividers through 50Ω cascade lines and metallized vias realize the interconnection of signals.After stacking design,total input port feeding structure design,basic power divider design and layout design,two sets of compact and integrated parallel feeding networks are developed,which are used for receiving and sending.The 12-element sub-array of the common antenna is fed by left-handed and right-handed circular polarization.The simulation results show that the insertion loss of the one to twelve power divider is less than12.98 d B and 12.88 d B,respectively,within the 10% bandwidth of the X-band of the left-handed and right-handed circularly polarized feeding networks.(3)Two forms of transition structure of microstrip line-microstrip line and microstrip linestrip line between the array antenna and the feeding network are designed,and the integration of the 12-element sub-array and the double feeding network is completed.Integrated design and simulation,and physical processing and testing have verified the correctness of the design scheme in this paper.The test results show that the isolation between the polarization ports of the array is greater than 19.15 d B,the axial ratio is less than 3.5d B,and the fluctuation ranges of the left-hand and right-hand circular polarization gain are 11.71 d Bi-13.32 d Bi and 10.82 d Bi-13.08 d Bi respectively.Compared with the existing design scheme,not only the gain and axial ratio performance are improved,especially,the number of metal layers in the multi-layer microwave board is reduced from 10 to 6 layers,the blind holes in the middle layer are saved,and significantly reducing processing complexity and antenna cost. |
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