Unit 5 Radio Frequency and microwave Applications Words and expressions History ext and notes Grammar Exercises Reading material 上海海事学信息工程学院
上海海事大学信息工程学院 Unit 5 Radio Frequency and Microwave Applications Words and expressions History Text and notes Grammar Exercises Reading material
Words and expressions (7 Active adj.有源的 Alleviate vt.减轻;缓和 ■ Antenna n.天线 ■ Carrier n.载波 a Cautery n.烙(术):烙器;烧灼剂 ■ Channel n.频道;信道 Coax n.同轴电缆 Collision n.碰撞;抵触 ■ Coordinate n.坐标(用复数) ■ Diffraction n.衍射 ■ Entity n.实体;存在;本质 ■ Hemorrhage n.出血 Incident adi.入射的,投在或射在一表面的 Interference n.干扰 ■| onosphere n.电离层 ■ Magnetism n.磁性;磁力 上海海学信息工程学院
上海海事大学信息工程学院 Words and expressions ◼ Active adj. 有源的 ◼ Alleviate vt. 减轻；缓和 ◼ Antenna n. 天线 ◼ Carrier n. 载波 ◼ Cautery n. 烙(术)；烙器；烧灼剂 ◼ Channel n. 频道；信道 ◼ Coax n. 同轴电缆 ◼ Collision n. 碰撞；抵触 ◼ Coordinate n. 坐标(用复数) ◼ Diffraction n. 衍射 ◼ Entity n. 实体；存在；本质 ◼ Hemorrhage n. 出血 ◼ Incident adj. 入射的，投在或射在一表面的 ◼ Interference n. 干扰 ◼ Ionosphere n. 电离层 ◼ Magnetism n. 磁性；磁力
Words and expressions 7 Meteorology n.气象学,气象状态□ Metropolitan a.大都市的 Optical adj.眼镜的;视力的;光学的 ■ Orientation n.定位;定向 Ozone n.新鲜的空气,[化]臭氧 Propagation n.(声波,电磁辐射等)传播 ■■■ Sterilization n.杀菌,绝育 Surveillance n.监视,监督 Via prep经由;取道 Cut-off frequency 截止频率 a Transverse MagnetIc (TM) 横磁(性)的 ■ Lay the foundation of 给.打下基础,为..奠定基础 Line-of-sight 视线,瞄准线 ■ Modulating signal 调制信号 上海海学信息工程学院
上海海事大学信息工程学院 Words and expressions ◼ Meteorology n. 气象学，气象状态 ◼ Metropolitan a. 大都市的 ◼ Optical adj. 眼镜的；视力的；光学的 ◼ Orientation n. 定位；定向 ◼ Ozone n. 新鲜的空气，[化]臭氧 ◼ Propagation n. (声波，电磁辐射等)传播 ◼ Sterilization n. 杀菌，绝育 ◼ Surveillance n. 监视，监督 ◼ Via prep.经由；取道 ◼ Cut-off frequency 截止频率 ◼ Transverse Magnetic (TM) 横磁(性)的 ◼ Lay the foundation of 给…打下基础，为…奠定基础 ◼ Line-of-sight 视线，瞄准线 ◼ Modulating signal 调制信号
History(from google James clark Maxwell: (1831-1879 In the 1860s and 1870s, James Clerk Maxwell developed the theory of electric and magnetic forces, summarized in his famous four equations. these equations encapsulated all that had been discovered about electricity and magnetism in the experiments done over the previous few hundred years by Faraday, Volta, and many others. They showed that electricity and magnetism were two aspects of the same force. The equations also predicted that there should be a form of radiation which came to be known as electromagnetic radiation Maxwell realized that light was a form of electromagnetic radiation Around 1862 he wrote We can scarcely avoid the conclusion that light consists in the transverse undulations of the same medium which is the cause of electric and magnetic phenomena The equations predicted that electromagnetic radiation could exist with any wavelength. The various colors of light have wavelengths less than a thousandth of a millimeter. Much longer wavelengths are possible 上海海学信息工程学院
上海海事大学信息工程学院 History (from google) ◼ James Clark Maxwell: (1831-1879) ◼ In the 1860s and 1870s, James Clerk Maxwell developed the theory of electric and magnetic forces, summarized in his famous four equations. These equations encapsulated all that had been discovered about electricity and magnetism in the experiments done over the previous few hundred years by Faraday, Volta, and many others. They showed that electricity and magnetism were two aspects of the same force. The equations also predicted that there should be a form of radiation, which came to be known as electromagnetic radiation. Maxwell realized that light was a form of electromagnetic radiation. Around 1862 he wrote, "We can scarcely avoid the conclusion that light consists in the transverse undulations of the same medium which is the cause of electric and magnetic phenomena." ◼ The equations predicted that electromagnetic radiation could exist with any wavelength. The various colors of light have wavelengths less than a thousandth of a millimeter. Much longer wavelengths are possible
History(from google) Oliver Heaviside(1850-1925 I Heaviside and Kennelly, in 1902, predicted that there should be an ionised layer(电离层) in the upper atmosphere that would reflect radio waves. They pointed out that it would be useful for long distance communication, allowing radio signals to travel to distant parts of the earth by bouncing off the underside of this layer. The existence of the layer, now known as the heaviside layer or the ionosphere, was demonstrated in the 1920s If radio waves bounce off the inside of the ionosphere, then they must also bounce off the outside so any radio waves from outside the earth would not get through to the ground -- they would bounce back into space a Thus the predictions by Heaviside, combined with Planck's radiation theory, probably discouraged further attempts to detect radio waves from the Sun and other celestial objects. For whatever reason, there seem to have been no attempts for 30 years, until Jansky's unexpected discovery in 1932 Later it was learned that the reflection from the ionosphere is very dependent on the frequency (or wavelength) it reflects most of the radiation of frequency less than about 20 MHz. but the ionosphere is not a barrier to frequencies above about 50 MHZ Radio astronomy had to wait for the development of high frequency radio receivers 上海海学信息工程学院
上海海事大学信息工程学院 History (from google) ◼ Oliver Heaviside (1850-1925) ◼ Heaviside and Kennelly, in 1902, predicted that there should be an ionised layer (电离层） in the upper atmosphere that would reflect radio waves. They pointed out that it would be useful for long distance communication, allowing radio signals to travel to distant parts of the earth by bouncing off the underside of this layer. The existence of the layer, now known as the Heaviside layer or the ionosphere, was demonstrated in the 1920s. ◼ If radio waves bounce off the inside of the ionosphere, then they must also bounce off the outside. So any radio waves from outside the earth would not get through to the ground -- they would bounce back into space. ◼ Thus the predictions by Heaviside, combined with Planck's radiation theory, probably discouraged further attempts to detect radio waves from the Sun and other celestial objects. For whatever reason, there seem to have been no attempts for 30 years, until Jansky's unexpected discovery in 1932. ◼ Later it was learned that the reflection from the ionosphere is very dependent on the frequency (or wavelength). It reflects most of the radiation of frequency less than about 20 MHz. But the ionosphere is not a barrier to frequencies above about 50 MHz. Radio astronomy had to wait for the development of high frequency radio receivers