The Application Of Low Dispersion "M(2,4)FDTD+FDTD" Scheme In The Low Frequency Ground-wave Propagation

Low tfrequency ground-wave of Loran-C navigation system makes up the weak signal and vulnerable jamming of the satellite navigation system.It has played a great role in civil and military navigation.At present,the main problem facing the development of the navigation accuracy is poor.Therefore,it has become the key to development for prediction of high precision low frequency ground-wave.In a low frequency ground wave navigation system,accurately predicting phase delay is the key in improving the accuracy of positioning,navigation,and timing(PNT).The finite-difference time-domain(FDTD)method has proven to be capable of improving system accuracy dramatically.However,it suffers from very high computational.To solve this problem,a combined "M(2,4)FDTD and traditional FDTD" low dispersion method is proposed to improve the accuracy therefore reduce cost of the numerical simulation.The idea of "M(2,4)FDTD+FDTD" low dispersion numerical calculation the method is ground-wave propagation space division of FDTD implementation around the surface of numerical calculation,M(2,4)FDTD to achieve regional air low mesh density of high precision calculation.The method can further reduce the numerical dispersion errors of the air region,While reducing memory resources occupied,improve the calculation speed,so as to further improve the FDTD algorithm in low frequency wave propagation prediction of numerical dispersion error,improve the accuracy of the prediction phase.This paper from the basic theory of the FDTD and M(2,4)FDTD algorithm,analyzes the numerical dispersion characteristics and knowable M(2,4)FDTD algorithm is introduced in the correction factor,reducing algorithm single frequency all along the direction of the numerical dispersion error,can significantly reduce the numerical dispersion error of FDTD.Subsequently,the paper studies the "M(2,4)FDTD+FDTD" low dispersion numerical calculation method,and describes the implementation of the algorithm,gives the simulation model,and the model is validated and performance evaluation.In the visual studio 2012 platform,using C++programming to achieve the simulation of low frequency ground-wave propagation,and verify the correctness and effectiveness of this method.In order to FDTD simulation results as a reference,and ''M(2,4)FDTD+FDTD" low dispersion algorithm results were compared,including smooth flat surface,uneven piecewise smooth flat surface and the influence of the uneven not smooth and flat.Through the "M(2,4)FDTD+FDTD" low dispersion numerical calculation method of LF ground-wave propagation field and phase prediction simulation results show that this algorithm can achieve high precision and fast phase delay prediction of the low frequency ground-wave propagation.