Calculation of Attenuation in Rain Medium with Realistic Rain drops Shapes Modeling by the FDTD Method

Total cross section (TCS) of rain drops with realistic shape model (Modified Pruppacher Pitter or MPP model) is calculated by Finite difference time domain (FDTD) method implemented in three dimensions. FDTD Results are validated by the volume integral equation (VIE) method through simulation of rain drop model in commercial software CST Microwave Design Studio. The accuracy of oblate spheroidal model as a simpler model for rain drops is also compared with MPP model results. Simulation are performed at the frequency of 30 GHz, in both vertical and horizontal polarizations of incident wave. TCS results are then used for the calculation of rain specific attenuation with Marshal-Palmer (M-P) rain drop size distribution (DSD). The specific attenuation of spheroidal and MPP rain drops models are calculated and compared for different rain rates in vertical and horizontal polarizations of incident wave. These results can be applied for applications with wave propagation in rainy mediums.