A Study Of Grazing-Incidence Multipath Model For Elevation Estimation In Metrewave Radar

Multipath effects have been one of the important problems on beam resolution and angle measurement up to the present day. Especially it degrades the estimation accuracy of the grazing-incidence target elevation. The metrewave radar gets the anti-stealth ability because of the comparability in size between operating wavelength and targets. However,it is more difficult to estimate target elevation in metrewave radar than microwave radar. By now, lots of methods have been proposed to solve the multipath effects based on different viewpoints. Among these methods, super-resolution algorithms have increased an interest in signal processing field. However, they almost used the multipath model which is with single reflection for simple point target. Up to now, little research on the multipath models for complex target is reported. So a kind of multipath models for complex target is presented in this paper.A multipath model is precise description of multipath propagation of radar echo. In order to build the model, two aspects are considered.First, multipath propagation of electromagnetic wave is discussed, including the reflection coefficient of mirror reflection and diffuse reflection, the effective reflecting region and reflecting point and the effects of non-uniform atmosphere on electromagnetic wave propagation. The reflection coefficient, which represents the change on the plane of reflection, is discussed in detail.Second, the target model with multi-scattering centers is described. In this model, the complex target can be represented by some discrete scattering centers. So, the research is begun with building the extended target model based on the multi-scattering center theory. Combining the extended target model with the characteristics of the reflecting surface and the targets'maneuver, the models for multi-scattering centers are presented.Comparing to the experimental data, the simulation results demonstrate that the multipath models presented here can describe the practical situation approximately by setting parameters. Furthermore, it can be concluded that there is relation between the multipath effects and the factors, the number of scattering centers, distribution of scattering centers and the reflection coefficient.