| The large loop communication link of maritime satellite communication buoy-low-orbit satellite-ship end is an effective way to realize high-speed real-time information communication between the deep-sea communication buoy and the ship-based information center.Low-orbit satellite communication has the advantages of small space attenuation and transmission delay,which is conducive to real-time return of ocean exploration data.In the process of low-orbit satellite-to-ground communication,it is necessary to adjust the antenna beam pointing in real time.The use of the phased array antenna can quickly adjust the beam pointing to the sea surface communication area,and can achieve large-angle wide-area coverage.At the same time,the antenna of the sea surface buoy also needs to track the satellite in real time in complex sea conditions.Therefore,it is of great significance to study the low-orbit satellite spaceborne phased array antenna technology and the sea surface tracking satellite antenna technology for satellite-ocean communication.This paper mainly studies the key technologies of L-band spaceborne phased array antennas used in low-orbit satellite satellite-ground communications.In order to meet the link requirements,a relay communication load is carried on the satellite with an altitude of about 500 km in low-Earth orbit.Through the analysis of the satellite-ground link,the paper proposes a spaceborne phased array antenna design scheme with 15+1 array elements,in which 15 array elements form the receiving unit and one array element serves as the transmitting unit.In the limited array size of340mm×340mm,this antenna not only meets the communication requirements,but also realizes the reliability,stability and low cost of spaceborne phased array antenna.The simulation analysis of the antenna element and the phased array by the simulation software is completed in this paper.The antenna unit is in the form of an orthogonally symmetric oscillator,using a slotted coaxial balun to balance the feed,no complicated feeding network is required,and a rectangular metal cavity is added at the bottom to improve the gain.The receiving antenna unit has a VSWR<1.5 and an axial ratio of less than 2d B in the 1.60～1.75 GHz frequency range.The dipole antenna forms a 4×4 square array by rotating the feed.The receiving array can scan in a wide angle range of ±60°,and the gain is in the range of 12.7～16.4d B.The phased array antenna receives sea surface signals with right-handed circular polarization,which is isolated by polarization from signals such as Beidou short messages,and a cavity filter is added at the back end of the antenna to improve the anti-interference ability.The thesis completes the calibration and testing of the phased array antenna in a microwave anechoic chamber.And calculate the pointing angle to the ground when the satellite transits the communication sea area,and then convert it into the azimuth angle and elevation angle under the coordinate system of the phased array antenna,so as to synthesize the correct pointing beam.The test results verify the ±60°wide-angle scanning characteristics of the active phased array antenna.In addition,the paper proposes a communication antenna design scheme for tracking satellites at the buoy terminal according to the complex sea conditions,and conducts a simulation analysis to lay the foundation for the follow-up work. |
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