Research On Design Technology Of UAV Aerial Survey GNSS Receive System

In recent years,along with the steady promotion of four major Global Navigation Satellite Systems of GPS,GLONASS,GALILEO,BDS(i.e.,GNSS),the navigation technology of GNSS gains tremendous growth driven by international cooperation among China,Russia,the United States and Europe,which work in a joint effort to build service platform,share service information and status information.Compared with the traditional positioning and receiving system based on the single satellite,navigation receiving technology of GNSS get significant improvement in positioning accuracy when put into practical use.It means a lot for both of social production and daily life,especially when applied in UAV aerial survey.The receiving system of GNSS is compatible with four major global navigation satellite system,which can achieve more real time satellites observation in positioning and thus avoid lock loss of satellites caused by losing the tracking satellites in UAV aerial survey.In addition,the positioning accuracy of the receiving system of GNSS gets great enhancement by combining RTK of the carrier phase difference and the Multifrequency differential technology.The UAV aerial survey has been extensively applied in all different kinds of application scenarios,including engineering survey,topographical reconnaissance,agricultural plant protection,etc.Due to high demand on precision and dynamic highaltitude operation,there remains particular requirements for faster and real time positioning technologies of UAV.What's more,continuous operation further calls for lightweight design of aerial system based on high positioning accuracy.Therefore,this paper aims to discuss the critical technologies of GNSS receiving system in the following aspects:(1)Analyze key technologies of GNSS receiving antenna design by studying the frequency features of GNSS signal.In the process of designing microstrip antenna with single layer radiation structure,the paper aims to change the distribution of radiated electric field and realize the resonance of the antenna at multifrequency by slotting radiation patch.In addition,circular polarization of the antennas is realized by considering both of the corner cut of the radiating element and feeding points of antennas so as to guarantee light weight.(2)Based on analyses of the structural features of GNSS signals and relevant principles of data acquisition and tracking,Fourier transform is used to convert the operation of captured GNSS signal and receiving code to frequency domain,which will be later converted to time domain through IFFT.By doing so,signal is successfully captured and the corresponding acquisition time is reduced.Moreover,high precision tracking of GNSS signal carrier and phase is achieved by Costas loop and DLL.(3)Research on the embedded interactive system of the UAV aerial system.Specially,Wifi module and UART interface of CPU Cortex-A8 guarantee reliable GNSS data transmission.Meanwhile,parsing original data from receiving terminals and calling data to the interactive interface for real-time monitoring makes it possible for interactive application of UAV.