Research On UAV Image Transmission Signal Detection And Modulation Recognition Method

With the increasing maturity of UAV technology,UAVs have been widely used in people’s daily life,such as aerial photography,power inspections,and news reports.But it also brought a series of security issues,such as UAVs "black fly",transporting drugs,peeping on the privacy of others,etc.,which have caused serious threats to society and people’s lives,and attracted wide attention from professionals in various countries.Therefore,research on anti-UAVs technology is imperative.This paper studies the detection,modulation recognition and related param eter estimation methods of UAV image transmission signals,which are the premise of countering UAV positioning technology in the field of UAV,and have important theoretical significance.The main research contents are as follows:(1)The communication system of the UAV is studied as the theoretical basis of the UAV image transmission signal detection and modulation recognition,and the architecture of the combination of the AD9361 radio frequency agile chip and the digital signal processing system on chip is used to design the unmanned Machine image transmission signal receiving system.(2)Research the detection method of civil UAV image transmission signal.UAV remote control signal is used as a frequency hopping signal,while the image transmission signal is a non-frequency hopping communication signal.The time-frequency analysis method is used to analyze the two kinds of signals.Continuous features to detect the presence of video transmission signals.At the same time,a detection method of image transmission signal based on power spectrum is proposed.By calculating the cancellation ratio between the average power spectrum of the signal and the original power spectrum,the characteristic of the image transmission signal cancellation ratio is used to judge whether the received signal is an image transmission signal.(3)The modulation recognition and related parameter estimation algorithms of civil UAV image transmission signals are studied.First,the high-order cumulant of the OFDM signal is used to realize the modulation recognition of the OFDM signal and the single carrier signal.The simulation shows that the recognition accuracy of the algorithm is higher than 97%when the signal-to-noise ratio is greater than-4dB.Secondly,the OFDM modulation is studied.Signal-related parameter estimation algorithms mainly include bandwidth estimation algorithms based on power spectral density,time-domain parameter estimation algorithms based on signal cycle characteristics,and bandwidth-based sub-carrier number estimation algorithms,and are used in different channels,different cyclic prefix lengths,and different subcarriers.Three parameter estimation algorithms are simulated under the four conditions of the number of carriers and the number of different symbols.The simulation shows that when the signal-to-noise ratio is greater than 0dB,the estimation accuracy of each parameter is higher than 91%.Finally,the use of image transmission signals for non-frequency hopping communication The signal,bandwidth is about 9MHz,and the modulation method is OFDM.The UAV image transmission signal receiving,detection and recognition system is designed.