[工程科技]微波遥感理论与技术基础2.ppt

微波遥感理论与技术基础（第二周） 董晓龙 国家863计划微波遥感技术实验室 中国科学院空间科学与应用研究中心 提纲 第二章：电磁波及其与物质的相互作用（2-4） 电磁波的基本参数与性质 电磁波与物质相互作用简介 电磁波波谱及其与物质相互作用的特点 物体的微波散射特性（面散射与体散射） 物体的微波发射特性 遥感探测的基本形式和微波遥感器 一、电磁波的基本参数与性质 The 1st requirement for remote sensing is to have an energy source to illuminate the target (unless the sensed energy is being emitted by the target). This energy is in the form of electromagnetic radiation. Electromagnetic radiation: consists of electrical field(E) : varies in magnitude in a direction perpendicular to the direction in which the radiation is traveling； magnetic field (M): oriented at right angles to the electrical field. Both E M fields travel at the speed of light (c). Transient and Harmonic EM Waves Form of time varying Transient-time domain description Waveform Time domain function Harmonic-frequency domain description Harmonic functions Sine or cosine representation The characteristics of EM waves: Frequency/wavelength Phase/time Amplitude Polarization Coherence Frquency/wavelength Phase/time Amplitude Amplitude Represents the energy carried by the EM waves; Orientation of E M fields Polarization directions Two different definitions: With respect to incident plane; With respect to ground plane. Polarization forms: Varying of polarization with time. Arbitrary polarized EM waves can be presented as the linear combination of two perpendicular polarization components. These two have different phase and amplitude relationships. Linear polarization H and V (polarization does not change with time) Circular polarization Right hand Left hand Elliptical polarization Representations of polarization Stokes vector Poincare Sphere Partial Polarized and Full Polarized Completely Unpolarized: Q=U=V=0; Completely Polarized: Paritally Polarized Coherence Coherence describes correlation of two different EM signals. 二、电磁波与物质的相互作用简介 电磁波谱 电磁波谱与物质运动的关系 Electromagnetic Spectrum Radio waves Microwaves Infrared Visible light Ultraviolet X rays Gamma ray