| Global navigation satellite system(GNSS)is dominated by the United States,which has been widely used in military,aerospace,geodesy and other aspects.In the process of positioning and navigation,interfere can be treated as multipath signals of real signals.Based on this,the main purpose of this paper is to design a multifunctional navigation signal source,which can generate real GPS navigation signals,and can simulate various characteristics of multipath signals in the communication environment.Firstly,this paper introduces the basic principle of GPS system in four aspects,the satellite navigation system,satellite navigation and positioning principle,parameter calculation algorithm,the satellite signal receiver parameters calculation algorithm.The satellite parameters and receiver parameters are calculated,and the results are given.Then,this paper presents the system model of multipath signals and the signal design method in two aspects,star selection strategy and interference location selection.The method is mainly based on the sensitivity of the satellite pseudo range variation in the process of position calculation by the receiver.In the aspect of star selection strategy,two methods,pseudo range method and projection method,are proposed in this paper.It is proved that the two methods are consistent in nature and can be used according to different application scenarios.In the selection of interference location,this paper demonstrates in two aspects: direction selection and value selection.Because the spatial distribution of navigation satellites is different,their traction on the direction of deviation is also different.Based on this,this paper proposes a method to select the traction direction based on the spatial distribution of navigation satellites.The selection of the deviation value is mainly to avoid the RAIM detection of receiver.In order to achieve the maximum deviation from the minimum cost,and to avoid being detected by the receiver as much as possible,this paper analyzes the influence of receiver RAIM detection algorithm on multipath interference in detail,and proposes a multipath signal generation algorithm.Simulation results show that when 3 multipath signals are used,the desired deviation can be achieved,and the RAIM detection of the receiver can be well avoided.Finally,the actual function test is carried out through the LabVIEW platform.The design method and software interface are given,as well as the setting parameters of every part.And the function of each part is analyzed.Among them,the receiver positioning results can be controlled by setting the receiver’s motion path and the gain and delay of multipath signals.The design of multipath signal generation is emphasized.In order to fully demonstrate multipath interference,the paper designs 5 kinds of deception model,point,line,circle,specific direction and trajectory.In each mode,by setting the multipath signal gain and delay to control the receiver positioning.The strategy and effect were verified by common Android mobile phone test,and the accuracy of the theoretical analysis is proved. |
