Parallel Time-Domain Method For EM Scattering From Rough Surface With/without A Target Based On CUDA

In recently years,Compute Unified Device Architecture(CUDA)based on GPU parallel technology has been widely applied in electromagnetic simulation.Compared to traditional CPU parallel technology,GPU can achieve a significant speedup with powerful computing capability under low hardware cost,which improves the computational efficiency greatly.As a numerical method in computational electromagnetic,the finite difference time domain(FDTD)method has an advantage of high computational precision.In addition,update of electric field(magnetic field)only needs its value last time step as well as neighbor magic field(electric field),and it isn't relative to the other cells,which is suitable for parallel design.Time-domain physical optics(TDPO)method has a significant advantage of analysis for transient response and wide-band scattering from rough surface.In the dissertation,the FDTD method and time-domain physical optics for electromagnetic scattering from rough surface with or without a target are investigated in detail.On a single GPU platform,the parallel strategies of FDTD for one-dimensional and two-dimensional rough surface scattering are illustrated and optimized in detail,respectively;Also TDPO for two-dimensional rough surface scattering is parallelized and optimized.Furthermore,the FDTD and TDPO for rough surface scattering are also parallelized on the multiple GPUs.The main works are listed in the following:1.Parallel design and optimization are studied for FDTD to calculate electromagnetic scat-tering from one dimensional rough surface with or without a target.The parallel program without optimization achieves a speedup of 74.49×.A speedup of 101.41 x is realized through optimizations by shared memory texture memory and asynchronous transfer tech-nology,which improves computational efficiency.Furthermore,CUDA-FDTD is utilized to investigate the impact of incident angle,mean square height,correlation length and permit-tivity on scattering characteristic of soil.Bistatic scattering coefficient of electrical large sea surface with electrical large target is calculated.The influence of wind speed,incline angle of missile,height of missile and depth of ship on composite scattering is analyzed.The CUDA-FDTD is utilized to study transient response and wide-band scattering from rough surface with a pulsed wave illumination.2.Parallel design and optimization are investigated for FDTD to calculate electromagnetic s-cattering from two dimensional rough surface with or without a target.A speedup of 40.16×is obtained though comparing different FDTD meshes by an unoptimized program.Further-more,shared memory and register are used to cache global memory to improve bandwidth,and a speedup of 46.00x is achieved.A speedup of 49.63x is obtained by the use of asyn-chronous transfer technology to hide data transfer between CPU and GPU.The influence of incident azimuth ?i,wind speed,temperature,salinity,as well as ice layer on scattering characteristic of sea is discussed.Meanwhile,the variation of bistatic scattering coefficient of buoy and sphere on sea surface with incident angle,wind speed,as well as depth of buoy and sphere is analyzed.Furthermore,characteristics of electromagnetic scattering from sea with ship and missile are examined.3.Smooth surface illuminated by terahertz(THz)wave becomes rough because the wave-length is rather small.Due to a electrically large problem at this wave band,it's a challenge for CPU memory and CPU time in THz scattering.The GPU-FDTD method is applied to analyze the scattering characteristic of one-dimensional and two-dimension rough surface as well as two-layered rough surfaces.Moreover,the scattering characteristics of rough surface are compared at microwave band and THz wave band.4.TDPO method is utilized to investigate electromagnetic(EM)scattering from 2D electrical large rough surface in time domain.The formulation of TDPO is presented,which derives the far field by transforming the equivalent electric current density and far-field expression in the frequency domain to those in the time domain.Far field wide-band repose is obtained by making Fourier transformation on time-domain scattered field.GPU is also employed to expedite the TDPO for computation of 2-D electrical large rough surface,and the parallel scheme and computation flow are given in detail.Shared memory is utilized to optimize determinant calculation and matrix solution referring to occlusion judgment.5.The FDTD method and TDPO for computing the electromagnetic scattering from the rough surface with or without the target are performed parallelly on the multiple GPUs based on the single GPU.The parallel FDTD is applied to compute the electromagnetic scattering from one-dimensional rough surface with or without a target.The parallel FDTD method is applied to calculate the rough surface scattering based on two GPU cards.In order to solve the problem that the calculation of rough surface electrical length is restricted by the global memory size,GPU 1 card is extended along i direction to widen application of FDTD.Also,two GPU cards are used to expedite the calculation of the scattering from two-dimension rough surface.Occlusion judgment is executed on GPU 0.Meanwhile,integral of triangle and Fourier transformation run on GPU 1.