| Satellite navigation systems are widely used in fields such as unmanned driving,agricultural machinery navigation,disaster monitoring,public transportation,and rescue,and have formed a huge industrial chain for military and civil use.With the gradual completion of the Beidou-3 satellite navigation system independently developed by China,satellite navigation and its applications have become research hotspots in Research field.At the same time,some theories and technologies have matured and become a paradigm.For example,undergraduate majors in communications engineering,Satellite Navigation has become a professional course.The course has the characteristics of close integration of theory and practice,theoretical abstraction,complicated formula derivation,large amount of calculation,and difficulty for beginners to get started.In the actual teaching process of the course,it is usually affected by factors such as limited experimental hardware conditions and insufficient teaching hours,which makes the students have insufficient theoretical depth and the corresponding technology cannot obtain the opportunity of perception and understanding through experimental practice,thus greatly reducing the teaching effect.In response to this situation,this article uses Matlab and STK as tools,with strong principle display,simple operation,flexible interaction,and progressive hierarchy as the experimental construction concept,combining the characteristics of basic theoretical knowledge and the needs of students at the initial stage Design the experiment with the mastered knowledge framework.Finally,in the form of pure software,this paper implements a series of GPS / BDS dual-mode satellite navigation experiments with a typical and practical knowledge of the key and difficult knowledge of the course,which is suitable for satellite navigation courses.Of experimental teaching:(1)From the perspective of the principle of satellite signal transmission,a spread spectrum communication simulation experiment was established.Three spreading codes,m-sequence,gold-sequence,and orthogonal gold-sequence,were generated.The modulation information generation,spread spectrum,modulation,demodulation,and despreading in the entire spread spectrum communication process were demonstrated step by step;(2)Set up a GPS C/A code simulation experiment from the perspective of satellite signal generation and transmission principles,and generate simulated navigation messages,C/A codes,L1 carriers,and corresponding processes such as spreading,modulation,and noise;(3)Set up a BDS pseudo-random code simulation experiment from the perspective of satellite signal generation and transmission principles,and realize the processes of generating navigation messages,generating pseudo-random codes,spread spectrum modulation,generating carriers,carrier modulation,and adding Gaussian white noise;(4)Set up a GPS C/A code acquisition experiment from the perspective of satellite signal reception principles,and verify the traditional acquisition method and parallel code phase search method to visually display the acquisition results.For these two algorithms,the acquisition time and carrier Comparative analysis of frequency,code phase and Doppler frequency shift;(5)Take all GPS navigation satellites as a whole,set up a GPS constellation simulation experiment,simulate the GPS constellation,design a visual simulation platform for the navigation constellation,establish a constellation scene,and analyze the visibility and accuracy factor of the GPS navigation constellation To analyze characteristics such as the coverage of a single target or area;(6)Treat all BDS navigation satellites as a whole,set up a BDS constellation simulation experiment,simulate the BDS constellation,design a visual simulation platform for the navigation constellation,establish a constellation scene,and view the BDS navigation constellation visibility and accuracy To analyze characteristics such as the coverage of a single target or area.This series of experiments covers the generation,transmission and reception of satellite navigation signals and the navigation constellation of satellite navigation systems,combining theoretical knowledge from shallow to deep systems.Through testing,each experimental process can be run and realized correctly.The pure software experiment form also greatly reduces the experiment cost,which is beneficial to the popularization of satellite navigation course experiment.In the teaching,teachers and students operate the simulation experiment platform to conduct experiments.Users can set their own initial conditions and modify variable parameters.Users can view the input and output graphics in the system at any time to obtain related phenomena,results,and various performance indicators.In the operation,users can make abstract theoretical knowledge specific Change.This allows students to gain an intuitive feeling,stimulates students' interest and motivation in learning,and achieves the purpose of this course experiment. |
