Study On Inversion Of Atmospheric Duct Parameter From GPS Signal Propagation

Atmospheric duct is an anomalous atmosphere structure which can traped partly electromagnetic wave propagation far beyond the horizon with less attenuation. The atmospheric duct phenomenon greatly affects the capability of radar, communication, reconnaissance and some other electromagnetic radiation systems. Therefore, forecasting the real-time refractivity parameters in radar working area is both theoretically and military value to the studies on radar, communication, reconnaissance, etc.This dissertation firstly presents a thorough research on the subject including the parameter description, the principle of formation and classification of the atmospheric duct, then the condition of the atmospheric duct appearing and characteristic of electromagnetic wave propagation in atmospheric duct are analysed. The propagation paths of GPS signal propagation in the standard atmosphere and atmospheric duct including surfure duct and elevated duct are simulated by Ray-tracing technique, the ray which trapped in the duct is examined with GPS signal elevation angle 0.1 degree. Using the standard split-step Fourier Transform method to solve parabolic equation, low elevation angle GPS signal propagation is studied in the atmospheric duct, in particular for the initial field and boundary conditions. The power distribution of GPS signal propagation in different kinds of the atmospheric duct is also derived and calculated. Finally, using GPS signal power distribution in space and propagation model, the objective function is established. According to the simulated annealing algorithm, the parameter of atmospheric duct profile is inversed, which leads to obtain atmospheric duct profile. The numerical results show that the inversion profile fits well with the real measurement profile.