| Research on Galileo satellite navigation system is significant, for Galileo is theonly satellite navigation system under constructed by Europe. With the first pair ofsatellites, IOV I and IOV II, launched successfully in2011, the development ofGalileo comes back to life again, which attracts more scholars’ attention toresearches on Galileo system. In this paper a software IF signal simulator forGalileo Satellite Navigation System in E1frequency band is designed and developedon c++platform, which can provide not only a good simulation environment fordesign and test of Galileo receivers, but also a platform for verification of newtechniques and new schemes of Galileo system.Firstly, basic information of Galileo satellite navigation system is introduced.Then BOC (Binary Offset Carrier) modulation technique applied in Galileo systemis presented, with its features, the reason why it is applied and power spectraldensity characters of modulated signal analyzed. In addition, the theory ofcoordinate systems transformation involved in Galileo software signal simulator isintroduced and analyzed.Secondly, the design scheme of the a software IF signal simulator for GalileoSatellite Navigation System in E1frequency band on C++platform is proposed, andthe mathematical model of the IF signal sent to user receiver RF frontend. Thedesign scheme is divided into4functional parts, which are respectively parameterssetting, pseudo-random code producing, navigation message generating andmulti-satellite signals compositing. The implementation principles of each part areanalyzed in detail, and then the specific implementation processes and callingrelationships of subprograms are presented.At last, the output IF signal produced by the proposed Galileo E1softwaresignal simulator is tested and verified based on matlab platform. The testing isdivided into4parts. First the time domain waveform and power spectrum density ofthe signal are simulated, and the simulated results are compared with theoreticalvalues and curves to prove their consistency. Second the simulation of satellitecapturing and tracking processes are verified, and the validity of the signal simulatoris confirmed furtherly. In the last, the data recovery process of the navigationmessage is simulated. The recovered data is demonstrated to be consistent to theoriginal ephemeris data, which finally proves the validity of the proposed Galileo E1software signal simulator in this paper. |
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