Research On Key Technologies For Over The Horizon Detection Of Radar Ship

The radar is the most important link in the modern naval battle. with the development of the science and technology, information warfare and electronic warfare is becoming the first combat mode in the war, how to give full play of the detection performance of the warship-radar has a close relation to the results of the battle, so accurately evaluating and predicting the spreading condition of the electromagnetic wave in the atmospheric environment has become the radar research focus.The atmospheric duct has a large negative refractive index gradient which can make the radio wave bent; especially when the curvature of the ray is beyond the earth itself, some of the ray can spread forward in the duct layer. The evaporation duct has a highest occurrence frequency and a longest duration in all kinds of the atmospheric duct, it can not only make the region where the radio wave would have reached appear the shadow zone, but also make the radio wave spread to a farther distance with a very strong signal, so it has a highest effect on the detection performance of the warship-radar.Several problems are discussed in the paper, such as observation method and prediction theory in the evaporation duct, distribution of the spatial field, and the key technique of over-the-horizon detection. The paper describes some concepts and characteristic parameters of the atmospheric duct, and then establishing the observation method and prediction theory of the evaporation duct, by introducing a similarity parameter—pseudo refractive index from the radio meteorological parameters, the modified refractivity of unstable atmosphere layer, stable atmosphere layer and neutral atmosphere layer is given. Through the analyzing the Helmholtz equation, the parabolic equation is got, and then the distribution of electromagnetic field is giving basing on the split-step Fourier algorithm. By building differential calculation method basing on ray tracing technology, the localization chart is drawn in the evaporation duct, and the error correction model is set up. Finally the simulation analysis of the shadow zone of radar which is caused by the evaporation duct is given. The results show that a certain area of shadow zone can be formed in the near-surface under the evaporation duct, and with the antenna height increasing, the starting position of the shadow zone is increasing constantly, and the shadow zone of radar is reducing. The distribution of the shadow zone is basically consistent with the standard environment.