Design And Implementation Of The Three Generation Of BDS Multi-frequency Satellite Signal Simulator

The three generation of BDS multi-frequency satellite signal simulator can provide analog satellite signals at any time and position in real time,and can generate high-precision and high-dynamic BDS satellite signals in various complex environments.In order to verify the performance of the three generation of BDS receiver,the satellite signal simulator is required to reproduce the BDS satellite signal under different conditions in real time.The three generation of BDS multi-frequency satellite signal simulator has guiding significance for the development of high performance and high steady state receivers.Based on the design and implementation of the three generation of BDS multi-frequency satellite signal simulator,this paper firstly analyzes the signal system of the B1 C and B1 I frequency.Describing the key technologies involved in the signal simulator such as BOC signal modulation,spatial coordinate synchronization,signal propagation error,satellite position and pseudorange real-time calculation and frequency synthesis.Analyze and compare the advantages of BOC modulation performance,and propose a method to calculate the frequency control word by using the carrier change rate during the interruption interval,and establish the simulation model of the three generation of BDS multi-frequency satellite signal simulator.The overall scheme of the three generation of BDS multi-frequency satellite signal simulator is designed.Firstly,the software and hardware development platform structure of DSP+FPGA is analyzed.Then the circuit of each sub-module is elaborated.Finally,Analyzing the algorithms of carrier and satellite position calculation,ephemeris update and message writing in DSP.The carrier generation,pseudo code generation and signal modulation of FPGA are elaborated in detail.The focus is on the user's motion track state,initial carrier phase,initial code phase,and frequency control words.At the end of the paper,the IF signal of the B1 C and B1 I generated by the satellite signal simulator was tested and analyzed by the spectrum analyzer.In order to verify the accuracy and stability of the analog signal,commercial receivers were used to test the positioning accuracy of the static state and motion state of the carrier for a long time.The test results are as follows:(1)The carrier is in a static state,using the ublox-m8 n receiver for positioning analysis,the overall accuracy of the positioning error is ±6m;(2)the carrier is set to a uniform motion scene,and the generator generates a signal consistent with the preset trajectory.The performance of the three generation of BDS multi-frequency satellite signal simulator meets the design standards.