Propagation Characteristic Of Polarized Wave In Complicated Rainy Condition

The target detection based on the polarized radar is the frontier domain in radar science.In complicated weather condition,the weather medium like rain and fog affects a lot of the polarized detection of radar target and this issue draws lots of attention.For example,the raindrop will be obviously ellipsoidal when the rainfall rate is big.At the same time,raindrops will be canted with special angle with the effect of the wind field.So,it is very important to find the optimal polarized detection of target in different weather condition.Aimed at this issue,the extended MIE scattering method is proposed in this paper.Then,we combine the method with the raindrops with Fisher distribution and the wind field to structure the complicated weather condition.Last,we simulate and analyze the optimal polarized detection of radar target in the complicated weather condition.This paper contains three parts:Firstly,some electromagnetic scattering calculation methods are described.Then,we propose the extended MIE scattering method according to the stretched transformation method to analyze the scattering properties.The extended MIE scattering method can be used to calculate the scattered field of the ellipsoidal raindrop with arbitrary canted angle and the incident wave can irrigate in arbitrary directions with arbitrary polarized pattern.The proposed method is used to analyze the polarized scattering properties of the raindrop and the simulation result is compared with the ones from the equivalent sphere method and the Rayleigh approximation method.From the comparison,we can see that the extended MIE scattering method can simulate the scattering properties of the raindrop well free of the frequency,and it is a numerical analysis method based on the classical MIE method.Secondly,we combine the proposed method with the raindrops with Fisher distribution and the wind field to structure the complicated weather condition.First,we get the Fisher parameters by data fitting.Then,the average wind model,wind shear model and the turbulence wind model are used to constitute the complicated wind field which can be used to simulate the canted angle distribution of raindrops in actual air,and the complicated weather condition is obtained.The polarized scattering properties of the complicated weather are simulated which is the basis to analyze the target detection in complicated weather condition.Last,we set the simulation scene according to the rain cell and the full-polarized radar and linear polarization wave are used to detect the target in complicated weather condition.The relation between the RCS and the scattering matrix is analyzed,so we can analyze the detection performance according to the target's scattering matrix.Firstly,we change the angle between the linear polarization wave and the horizontal direction to analyze the relation between the scattering properties and the linear polarization pattern with the weather condition unchanged.Then,the weather condition will change as the time goes,and we analyze the target's scattering properties in different weather condition with the linear polarization pattern unchanged.The proposed method in this paper,the extended MIE scattering method,can be used to analyze the polarized scattering properties of the ellipsoidal raindrops with arbitrary incident direction of the incident wave free of frequency.Because the proposed method is not limited by the frequency,it can be used to analyze the scattering properties of the radar wave in X band or higher band when the radar is working in rain.Using three wind models to simulate the wind field can reflect the true angle distribution of the raindrops.Different complicated weather condition can be simulated setting different parameters.We get the conclusion that the detection result will usually be well if the horizontal polarized radar wave is used and we will get the optimal polarized detection if we adjust the polarized angle according to the weather condition.