【作者】 柳碧澜；

【导师】 张钦宇；

【作者基本信息】 哈尔滨工业大学 ， 通信与信息系统， 2009， 硕士

【摘要】 超宽带信号是就信号的相对带宽而言,当信号的带宽与中心频率之比大于25%时称为超宽带信号。超宽带电磁波因其频带宽、分辨率高、回波信号能携带被测目标丰富的特征信息等特点,被广泛应用于目标探测和成像领域。本文利用时域有限差分方法对室内环境下电磁波传播特性进行了数值模拟。分别仿真验证了二维,三维情况下FDTD方法的有效性,分析了超宽带脉冲源的性质以及传播特性。本文所做的工作就是基于电磁波的基本理论:首先介绍了FDTD格式以及各分量节点的取法。然后介绍了FDTD方法的数值稳定性和数值色散问题:包括时间间隔的稳定性要求以及Courant稳定性条件--即空间步长和时间间隔之间所需满足的关系。此外,还介绍了时域有限差分方法的边界条件:先从波动方程角度介绍了FDTD的吸收边界条件,由此引出了Mur的一阶、二阶条件;然后又介绍了一种吸收效果较好的完全匹配层(PML)吸收边界条件。通过分析FDTD的基本算法和将其应用于超宽带电磁脉冲信号的仿真研究需特殊处理的一些方面,建立超宽带电磁脉冲信号传播的FDTD二维及三维算法。分析超宽带电磁脉冲在空气中的能量衰减特性。以FDTD方法理论为基础,制定程序流程,利用MATLAB 7.0软件编程实现。分别以自由空间中高斯脉冲源问题和电偶极子辐射问题为例对程序进行了校验,数值模拟结果与解析结果能很好地符合,证实了所编写程序的有效性和正确性。分析了超宽带电磁脉冲在空气中及在室内环境下与物体作用的传播特性。同时数值模拟分析比较了PML层FDTD仿真中的作用。最后数值模拟分析了超宽带电磁脉冲信号在实际成像中的一个简单应用:模拟简单的室内环境进行FDTD模拟仿真。更多还原

【Abstract】 A signal is called an Ultra-band signal (UWB) if its ratio of bandwidth to center-frequency exceeds 25%. Since it has many advantages such as high frequency bandwidth, high resolving power, its echo can take abundant characteristic information of the detected target, it has been widely used in target detection and imaging technology. In this paper, the response characteristic of ultra-wideband in indoor environment is simulated numerically based on Finite Difference Time Domain Method. Based on time domain Maxwell Equation, the basic theory of FDTD Method of two-dimensional and three dimensional under Cartesian coordinates are introduced in detail, and the validity of FDTD method is verified by simulation on propagation of UWB pulse in free space.This paper is based on the basic principle of electromagnetic wave. The FDTD formulation and cell concept are introduced in two-dimensional and three-dimensional Cartesian coordinates. And then, the stability and numerical dispersion of the FDTD method are investigated. The absorbing boundary conditions for FDTD are also discussed in this paper. We first derive the Mur’s absorbing boundary conditions, then, an efficient boundary condition is introduced, which is so-called perfectly matched layer(PML).This paper builds the two-dimensional and three-dimensional FDTD algorithm of UWB EM pulse propagation based on the electromagnetic wave principle and FDTD algorithm. We analyze energy attenuation character of UWB in free space and other dielectric objects. Based on theory of FDTD method, we realizing the simulation of FDTD method using MATLAB 7.0 software. The validity and correctness of the simulations are verified by researching on propagation of Gaussian pulse and electric dipole transmitted in free space. And the result turns out the numerical solutions are consistent with analytic solutions. We also analyze the function of the PML layer in FDTD simulation. Finally, we did simulation in an indoor environment using the FDTD method.更多还原