微波技术与天线PPT.ppt

Chapter6 Antenna Basics  天线基础;Horn Antenna喇叭天线;偶极子;反射器;八木-宇田天线;天线阵;电基本振子;Near-Zone Fields 近区场;Far-Zone(Radiation) Fields 远区场;Spherical polar coordinates球坐标;;Antenna Pattern 天线的方向图;Common Types of Antenna Patterns 天线方向图的一般类型 Power Pattern - normalized power vs. spherical coordinate position. 功率方向图：基于球坐标的归一化功率图。 Field Pattern - normalized |E| or |H| vs. spherical coordinate position 场方向图：基于球坐标的归一化的电场或磁场的模值。;Isotropic Pattern - an antenna pattern defined by uniform radiation in all directions, produced by an isotropic radiator (point source, a non-physical antenna which is the only nondirectional antenna). ;Directional Pattern - a pattern characterized by more efficient radiation in one direction than another (all physically realizable antennas are directional antennas). ;Omnidirectional Pattern全向方向图;E-plane - the plane containing the electric field vector and the direction of maximum radiation. E平面-包含电场矢量和最大辐射方向的平面 H-plane - the plane containing the magnetic field vector and the direction of maximum radiation. H平面-包含磁场场矢量和最大辐射方向的平面;Antenna Pattern Parameters 描述方向图的参数;Side Lobe：旁瓣;Half-Power Beamwidth (HPBW) - the angular width of the main beam at the half-power points. 半功率波束宽度：主波束半功率点之间的夹角 First Null Beamwidth (FNBW) - angular width between the first nulls on either side of the main beam. 第一零点波束宽度：主波束两边第一个零点之间的夹角 ;;;Solid Angle立体角;在球面坐标下面元dA的表达式:;Radiation Power Density辐射功率密度;Radiation Intensity辐射强度;例题1：一个理想的等方向性辐射源的辐射强度为U0， 求其辐射的功率为多少，功率密度为多少？;Directivity方向系数;例题2：理想的等方向性辐射源的方向系数为多少？;例题3：电基本振子(电偶极子) 的方向系数为多少？;天线效率 Antenna Efficiency;Antenna Gain天线增益 ;Antenna Input Impedance天线的输入阻抗;辐射电阻Radiation Resistance;例题：求电基本振子的辐射电阻。;Definition: The polarization of the wave transmitted by the antenna. 定义： 天线辐射波的极化。; 辐射波的极化 Definition: The polarization of radiated wave is defined as that property of an electromagnetic wave describing the time varying direction and relative magnitude of th