Design And Realization Of Long Wave Timing Signal Simulator

The Loran-C navigation system is greatly affected by factors such as the terrain and surface parameters on the propagation path,therefore,the development and performance verification of the receiver requires a large number of field tests.This is time-consuming and laborious.The existing simulator mainly lies in the generation of ideal signal,or simple channel noise,while not considering the influence of the ground parameters on the transmission path and the terrain fluctuation on the signal field strength,delay and deformation.This limitation makes the dynamic receiving point analog signal not accurate enough.So it is very important to study the long wave timing signal simulator for the development of the receiver.This paper analyzes the influence of terrain undulation and geodetic parameters on the amplitude and secondary phase delay of the long-wave timing signal.At the same time,the influence of complex terrain on the deformation of the signal is also considered.A design method of long-wave timing signal simulator based on complex terrain is proposed.On this basis,software design and hardware implementation are carried out.The work is as follows:Firstly,the function and composition of Loran-C system are briefly introduced.The pulse format and broadcast format of Loran-C signal are studied,and the coding and modulation modes of Loran-C signal are analyzed.Both the signal pulse group of the main station and the sub-station are simulated.Secondly,the software coding and modulation of the long wave timing signal are completed.The attenuation factor of ground wave on complex path is calculated by integral equation method,and the amplitude and phase are extracted.Fourier analysis is used to calculate the long wave timing signal,which is closer to the actual waveform.The simulation of the mixed station signal was continued,and the decoding verification was carried out.Thirdly,the overall design framework of the long-wave timing signal simulator is listed.The design of upper computer interface of the simulator is completed.The signal control parameters are calculated according to the parameters set by the user,and the timing message coding is generated.Besides,the signal communication control module is designed,the storage of signal control parameters is realized,and the software design of the simulator is completed.Fourthly,the control parameter reception,data processing,pulse modulation and signal coding are completed on the hardware development platform.At the same time,the signal is simulated by hardware.The digital signal of long-wave timing station is obtained.The signal is decoded and verified by outputting analog signal through digital-to-analog module.The hardware implementation of the long-wave timing signal simulator is completed.This paper has completed the design of a long-wave timing signal simulator based on complex terrain.At the same time,it provides navigation signals closer to the actual transmission path for the development,debugging,testing and maintenance of the receiver equipment of the long-wave timing system.