电子科技大学：《无线系统中的微波与射频 Microwave and RF Design in Wireless Systems》课程教学资源（课件讲稿）ch04 Antennas and Propagation for Wireless System

●●● ●●●● 5.Directivity ●●●●● ●●●0 ●●●●0 ●●●0 Definition: ●●●● ●● The ratio of the maximum radiation intensity in the main beam to the average radiation intensity over all space: 主瓣最大辐射强度与整个空间平均辐射强度之比 max 4π max 4nUmax U avg Prad ∫2U(0,9)sin6a6d0 Pna=∫∫UsinOd0do =4πUmg 4 Foma+oma） （af+,）sn6wouo 101g D (dB) 16

5．Directivity Definition: The ratio of the maximum radiation intensity in the main beam to the average radiation intensity over all space:       max max max 2 0 0 2 2 max max 2 2 2 0 0 4 4 , sin 4 sin avg rad UU U D U P U dd F F F F dd                                ＝ 10lg D   dB 2 0 0 sin 4 rad avg avg P U dd U               16 主瓣最大辐射强度与整个空间平均辐射强度之比

●●● ●●●● 6.Radiation Efficiency ●●●●● 辐射效率 ●●●0 ●●●●0 ●●●0 ●●●● Definition: The ratio of the desired output power to the supplied input power 辐射功率与输入功率之比 erad Pn-Pos=1- Pin Nonperfect metal,dielectric material->inherent 非理想金属，介质损耗均来自内部 Impedance mismatch,Polarization mismatch-> External to the antenna,could be eliminated. 阻抗失配，极化失配均可以消除 17

6．Radiation Efficiency Definition: The ratio of the desired output power to the supplied input power 辐射功率与输入功率之比 in loss in in loss in rad rad P P P P P P P e      1 Nonperfect metal, dielectric material inherent 非理想金属，介质损耗均来自内部 Impedance mismatch, Polarization mismatch  External to the antenna, could be eliminated. 阻抗失配，极化失配均可以消除 17 辐射效率

●●● ●●●● ●●●●● ●●●0 7.Gain ●●●●0 ●●●● ●●● ● ● Definition:the product of directivity and efficiency 方向性系数与效率的乘积是增益 G=eaa·D=l10lgG(dB) ea=63%=-2dB,D≈32400=45dB,G=43dB 18

7．Gain Definition: the product of directivity and efficiency G  erad  D  10lg G dB e D rad＝63％＝-2 ， ＝ dB 32400 45dB, G=43dB  18 方向性系数与效率的乘积是增益