Research On Beam Measurement System Of Radio Telescope Based On UAV

Beam pattern is an important parameter for radio telescopes.For the limitation of signal frequency and intensity in astronomical measurement,this paper designs a beam measuring system for radio telescopes based on drones.The beam of the Tianlai telescope is measured through this drone-based system.The beam measuring principle and method of using the drone are analyzed from the astronomical measuring theory.Some key problems of this method like electromagnetic compatibility,high precision measurement of drone attitude,data matching between drone attitude measurement and power reception are studied.The overall system hardware includes drone,signal transmitting system,drone attitude measuring system and receiver system.The system software is composed of drone attitude measuring,path planning and data processing.The half wave dipole is designed as the transmitting antenna,which realizes the polarization matching to the feed in the telescope.The suitable devices of signal transmitting system like signal source,filter,attenuator and others are selected according to the link calculation.A data collection system of drone attitude measurement is developed through the drone secondary development,which solves the problem of data matching between drone attitude measurement and power reception.The software for path planning and data processing is also designed.The analysis of electromagnetic compatibility and the result of verification experiment show that the measuring system can meet the requirements of beam measurement for radio telescopes.The electromagnetic simulation software CST is used to simulate the beam pattern of three modules: the feed of telescope,a single dish telescope and the telescope array.The comparison between simulation and measurement is used to verify the accuracy of both beam research methods,which can help improve the design technique of radio telescopes.Selecting the dish telescope as the measuring object,the whole measuring process includes flight path planning,noise measurement,drone measurement,and data processing.Comparing with the Cassiopeia A,the beam range is expanded to the fourth side lobe by the drone.The amplitude difference within the half power beam width of two results is less than 1d B,which proves the accuracy of the drone measurement.Comparing with the simulation of telescope array,the angle difference of position and width of side lobes is within 1 °,which verifies the validity of drone measurement and simulation.The results with different flight height and time shows good agreements,which shows that the drone measurement is stable.The drone-based approach of beam pattern measurement is flexible and controllable,which has a good prospect of the beam measurement for radio telescopes.The beam measurement of the Tianlai radio telescope will lay the foundation for the calibration in astronomical observations.