Research And Verification Of Key Technology Of Interference Source Direction Finding On UAV Platform

In current satellite television broadcasting,the non-encrypted direct retransmission feature of the satellite transponder makes it easy for criminals to use the ground-side satellite uplink transmitter to interfere with and suppress normal television broadcasting.This project aims at this phenomenon,based on a single unmanned platform for low-altitude satellite uplink signals for spectrum monitoring and interference source orientation.In this paper,a single direction-finding link is designed to perform direction finding on the incoming wave signal,which supports the positioning of the late interference source and completes the physical layer link design and board verification.The article first compares the commonly used radio direction finding methods.According to the actual needs of the project,a single baseline interferometer direction finding mode is used.Some of the indicators were analyzed to illustrate the feasibility of implementation and a complete single-machine direction finding solution was proposed.The main content of this article includes the following aspects:First,a single baseline interferometer direction finding algorithm was designed and performance simulations were performed for the technical specifications.The algorithm adopts the phase difference-based unambiguous direction finding scheme.According to the actual hardware design,the system calibration algorithm is proposed and the influence of the channel and the hardware itself is eliminated.Measurable signal bandwidth of 5 0 0 K H z :5 M H z,including most of the satellite uplink signal bandwidth;direction error can be guaranteed within 10°,because it is low-altitude measurement,positioning accuracy within 200 meters,fully meet the design requirements.Since the positioning data is transferred into the frequency domain for measurement,the waveform modulation method,the power size,and other factors are less affected,so the range of the measurable signal is wide.Second,according to the single baseline no-fuzzy direction finding algorithm and calibration algorithm,the implementation of FPGA hardware code is accomplished by using system generator graphical development method,including data calibration,buffering,frequency domain conversion,calibration,smooth accumulation,parameter solving,and several function modules.According to the data flow processing flow,the implementation of each functional module is described in detail.Some functions of calibration and direction finding are similar.In the design,automatic switching is used to reuse functions,which saves hardware resources.Third,the functional verification of the direction-finding link was performed on the u SDR software radio platform designed by the team.The signal input and output of each function module was tested first,and the correctness of the module function was verified.After the transceiver link is synthesized and tested in the actual channel,compared with the fixed-point simulation,the error in the direction-finding accuracy is within 10°.The unambiguous direction finding algorithm and its implementation scheme designed in this paper have met the design requirements.The test results in the actual channel have been effectively verified and have certain theoretical and practical values.Can provide reference and support for similar direction finding and positioning technology.