An Accurate Modeling Method for Near-field Echo Characteristics

In order to study the near-field target characteristic of the radio fuse, an accurate near-field echo characteristics modeling algorithm based on Physical optics (PO) and physical theory of diffraction (PTD) and shooting and bouncing rays (SBR) methods is proposed to calculate the echo characteristics of fuse, including echo power and echo signal and RCS. This method fully considers the characteristics of near-field, such as the influence of antenna pattern, spherical wave irradiation, distance, polarization and so on. The main research work in this paper involves the followings: (1) Firstly, the expression of near-field irradiation field is presented as spherical wave propagation mode, which takes into count the influence of the near-field distance and spherical wave irradiation. (2) Establishing the system coordinate of antenna and the system coordinate of antenna local polarization, and then define the directivity function of near-field antenna to characterize the antenna pattern, local irradiation and near-field polarization conversion characteristics. (3) Introducing near-field polarization scattering matrix to unify the scattering characteristic components of different scattering mechanisms, and then calculate the echo characteristic of radio fuse by integrating those of the geometrical elements which are illuminated by antenna beam during missile target encounter. In addition, the proposed theoretical model in this paper is calibrated by actually-measured data. And the emulation results are with a good agreement with measured results. Finally, we consider a simplified missile model, and compute its echo characteristics under different antenna pattern and different distance and different polarization. The results show that scattering peaks correspond to the points of the wings of the missile. In addition, the results change obviously when using different antenna pattern. At the same time, the results are different under the different distance. Numerical results prove the proposed method high efficiency and preciseness. It would be especially valuable in engineering application.