信息科学与电子工程专业英语Lecture

1、1任爱锋电子(dinz)工程学院 E-mail: afren Office: 新科技楼A901 Phone: 88202830-607 Mobile:六十七页2Unit 3 电磁场, 天线(tinxin)和微波EM Fields, Antenna and MicrowavesUnit 3-1 电磁场Electromagnetic Field 共六十七页3New Wordsvicinity邻近，附近stationary 静止的，不变的charge 电荷quantum 量子photon 光子oscillate 振荡atom 原子ultraviolet 紫外线的catast

2、rophe 大灾难，大祸photoelectric effect 光电效应emission 发射，散发metallic 金属的incident 入射的eject 喷射，强制离开 electrodynamics 电动力学dynamics 动力学gravitational 重力的entity 实体共六十七页4The electromagnetic field is a physical field produced by electrically charged objects. It affects the behavior of charged objects in the vicinity

3、of the field. The electromagnetic field extends indefinitely throughout space and describes the electromagnetic interaction. It is one of the four fundamental forces in the nature (the others are gravitation, the weak interaction, and the strong interaction) 电磁(dinc)场是由带电物体产生的物理场。它会影响场附近的带电物体的行为。电磁(

4、dinc)场在空间无限延伸，描述电磁(dinc)相互作用。它是自然界中四个基本作用力之一（其余为万有引力，弱相互作用，强相互作用）。Unit 3-1 电磁场共六十七页5The field can be viewed as the combination of an electric field and a magnetic field. The electric field is produced by stationary charges, and the magnetic field by moving charges (currents); these two are often des

5、cribed as the sources of the field. The way in which charges and currents interact with the electromagnetic field is described by Maxwells equations and the Lorentz force law. 电磁场可以看成是电场和磁场的结合(jih)。电场是由静止电荷产生的，磁场由运动电荷（电流）产生；这两种（电荷）通常被描述为电磁场的源。电荷和电流与电磁场相互作用的方式由麦克斯韦方程组和洛伦兹力定律所描述。Unit 3-1 电磁场共六十七页6From

6、 a classical point of view, the electromagnetic field can be regarded as a smooth, continuous field, propagated in a wavelike manner, whereas from a quantum mechanical point of view, the field can be viewed as being composed of photons. 从经典的角度，电磁场可认为是平滑、连续的场，以波动方式传播；而从量子力学的角度，场可看作(kn zu)是由光子组成的。Unit

7、 3-1 电磁场共六十七页7The electromagnetic field may be viewed in two distinct ways.Continuous structure: Classically, electric and magnetic fields are thought of as being produced by smooth motions of charged objects. For example, oscillating charges produce electric and magnetic fields that may be viewed i

8、n a “smooth”, continuous, wavelike manner. 电磁场可用两种截然不同的观点来看。连续结构：经典地，电场和磁场被认为是由带电物体的平滑运动产生(chnshng)的。例如，振荡电荷产生(chnshng)电场和磁场，可看成光滑的、连续的波动方式。Unit 3-1 电磁场电磁场的结构(jigu)共六十七页8In this case, energy is viewed as being transferred continuously through the electromagnetic field between any two locations. For

9、instance, the metal atoms in a radio transmitter appear to transfer energy continuously. This view is useful to a certain extent (radiation of low frequency), but problems are found at high frequencies (see ultraviolet catastrophe). This problem leads to another view. 这时，能量可以看成是在任意两个位置之间通过电磁场连续地传递。例

10、如，在无线电发射机中的金属原子（看来(kn li)是）连续地传递能量。这个观点在一定程度上（低频辐射）是有用的，但是高频时就有问题（如紫外灾难）。由此产生了另一种观点。Unit 3-1 电磁场电磁场的结构(jigu)The ultraviolet catastrophe, also called the Rayleigh-Jeans catastrophe, was a prediction of early 20th century classical physics that an ideal black body at thermal equilibrium will emit radi

11、ation with infinite power. 共六十七页9Discrete structure: The electromagnetic field may be thought of in a more “coarse” way. Experiments reveal that electromagnetic energy transfer is better described as being carried away in photons with a fixed frequency. Plancks relation links the energy E of a photo

12、n to its frequency n through the equation: E = h n离散结构：电磁场可以一种比较“粗略”的方式来考虑。实验表明：电磁场的能量传递可以更好地描述(mio sh)为用固定频率的光子来传递。普朗克的关系式将光子的能量E及其频率v 通过下式联系起来：E = h nUnit 3-1 电磁场电磁场的结构(jigu)共六十七页10where h is Plancks constant, named in honor of Max Planck, and n is the frequency of the photon. For example, in the

13、photoelectric effect the emission of electrons from metallic surfaces by electromagnetic radiation it is found that increasing the intensity of the incident radiation has no effect, and that only the frequency of the radiation is relevant in ejecting electrons.1其中h是为纪念马克斯普朗克而命名的普朗克常量。v是光子的频率。例如在光电效应

14、中，即因电磁辐射(din c f sh)而从金属表面发射电子的现象，我们发现增加入射辐射的强度并无影响，只有辐射频率与发射的电子有关。Unit 3-1 电磁场电磁场的结构(jigu)共六十七页11This quantum picture of the electromagnetic field has proved very successful, giving rise to quantum electrodynamics, a quantum field theory describing the interaction of electromagnetic radiation with

15、charged matter.已经证明电磁场的量子描述是非常成功的，引出了量子电动力学。量子电动力学是一种描述电磁辐射(din c f sh)与带电物体之间相互作用的量子场理论。Unit 3-1 电磁场电磁场的结构(jigu)共六十七页12In the past, electrically charged objects were thought to produce two types of field associated with their charge property. An electric field is produced when the charge is station

16、ary with respect to an observer measuring the properties of the charge and a magnetic field (as well as an electric field) is produced when the charge moves (creating an electric current) with respect to this observer. 过去，认为带电物体会产生与它们电荷性质有关的两种场。相对于测量电荷性质的观察者，电荷静止时产生电场(din chng)，电荷运动（产生电流）时产生磁场（和电场(d

17、in chng)）。Unit 3-1 电磁场电磁场的动力学(Dynamics of the electromagnetic field)共六十七页13Over time, it was realized that the electric and magnetic fields are better thought of as two parts of a greater whole the electromagnetic field.2 随着时间的推移(tuy)，人们认识到电场和磁场是电磁场这一整体的两个部分。Unit 3-1 电磁场电磁场的动力学(Dynamics of the elect

18、romagnetic field)共六十七页14Once this electromagnetic field has been produced from a given charge distribution, other charged objects in this field will experience a force (in a similar way that planets experience a force in the gravitational field of the Sun). If these other charges and currents are co

19、mparable in size to the sources producing the above electromagnetic field, then a new net electromagnetic field will be produced.3 一旦给定的电荷分布产生了电磁场，那么(n me)在电磁场中的其它带电物体就会受到一个力的作用（就像行星受到太阳重力场的力一样）。如果这些电荷和电流的大小与产生上述电磁场的源是可比的，那么(n me)将产生一个新的净电磁场。Unit 3-1 电磁场电磁场的动力学(Dynamics of the electromagnetic field)

20、共六十七页15Thus, the electromagnetic field may be viewed as a dynamic entity that causes other charges and currents to move, and which is also affected by them. These interactions are described by Maxwells equations and the Lorentz force law. 这样，电磁场可以认为是一个动力学实体，它促使其它电荷和电流(dinli)运动，同时又受它们影响。这些相互作用可由麦克斯韦方

21、程和洛伦兹力定律来描述。Unit 3-1 电磁场电磁场的动力学(Dynamics of the electromagnetic field)共六十七页16Unit 3 电磁场, 天线(tinxin)和微波EM Fields, Antenna and MicrowavesUnit 3-2 微带天线Microstrip Antenna共六十七页17New Wordsmicrostrip antenna 微带天线patch 片fabricate 制造etch 蚀刻insulate 绝缘dielectric 介电的，电介质substrate 基底rectangular 矩形的elliptical 椭圆

22、的eschew 避开spacer 定位架子robust 牢固，稳健profile 轮廓，姿态conformable 适合的，顺从的UHF (ultra-high frequency) 特高频dBi (decibel isotropic) 全向性分贝resonant 谐振的lithographic 平板印刷的transmission line 传输线fringe 加边饰，条纹共六十七页18New Wordsimpedance 阻抗cavity 空腔polarization 极化，偏振diversity 多样，差异性asymmetric 非对称的virtual shorting plane 虚拟短

23、路平面共六十七页19In telecommunication, there are several types of microstrip antennas (also known as printed antennas) the most common of which is the microstrip patch antenna or patch antenna. A patch antenna is a narrowband, wide-beam antenna fabricated by etching the antenna element pattern in metal tra

24、ce bonded to an insulating dielectric substrate with a continuous metal layer bonded to the opposite side of the substrate which forms a ground plane.1 通信中，有几种微带天线（又叫印刷天线），其中最普通的是微带片状天线 或片状天线。片状天线是一种窄带宽波束(bsh)的天线，通过将天线单元图样蚀刻到粘贴在绝缘基底上的金属轨迹而制成，基底的另一面则粘贴连续的金属层形成接地平面。Unit 3-2 微带天线共六十七页20Common microstri

25、p antenna radiator shapes are square, rectangular, circular and elliptical, but any continuous shape is possible. Some patch antennas eschew a dielectric substrate and suspend a metal patch in air above a ground plane using dielectric spacers; the resulting structure is less robust but provides bett

26、er bandwidth. 通常微带天线辐射器的形状有正方形的，矩形的，圆形的和椭圆的，而任何连续的形状都是可以。一些片状天线为了避免绝缘基底，在接地平面的上空用绝缘逆电流器悬挂(xungu)一个金属贴片；这种结构的鲁棒性不是很好，但能提供更好的带宽。Unit 3-2 微带天线共六十七页21Because such antennas have a very low profile, are mechanically rugged and can be conformable, they are often mounted on the exterior of aircraft and spac

27、ecraft, or are incorporated into mobile radio communications devices.2因为这种天线外形低矮，机械强度大，并且形状上适应性强，通常装在飞机或太空飞行器外表，或组合在移动(ydng)无线电通信设备上。Unit 3-2 微带天线共六十七页22Microstrip antennas are also relatively inexpensive to manufacture and design because of the simple 2-dimensional physical geometry. They are usual

28、ly employed at UHF and higher frequencies because the size of the antenna is directly tied to the wavelength at the resonant frequency. A single patch antenna provides a maximum directive gain of around 6-9 dBi. 因为其简单的二维形状，所以微带天线的生产和设计相对来说不算(b sun)太贵。微带天线通常用于UHF（超高频）和更高的频率，因为天线的尺寸直接受制于谐振频率的波长。一个简单的片

29、状天线可以提供最大为69dBi的定向增益。Unit 3-2 微带天线dBi: decibel isotropic, the forward gain of an antenna compared with the isotropic antenna, which uniformly distributes energy in all directions. 共六十七页23 It is relatively easy to print an array of patches on a single (large) substrate using lithographic techniques.

30、Patch arrays can provide much higher gains than a single patch at little additional cost; matching and phase adjustment can be performed with printed microstrip feed structures, again in the same operations that form the radiating patches. 通过平板印刷技术我们很容易在单个大绝缘体上印刷贴片阵列。以很少的额外成本，贴片阵列比单个贴片能提供更高的增益，用形成辐射

31、电波的片状微带天线的同样机理，可对印刷微带天线的馈电结构进行(jnxng)匹配和相位调节。Unit 3-2 微带天线共六十七页24The ability to create high gain arrays in a low-profile antenna is one reason that patch arrays are common on airplanes and in other military applications. 以低矮的天线构成高增益阵列的能力(nngl)是片状天线广泛用于飞机和其他军事应用的原因之一。Unit 3-2 微带天线共六十七页25The most comm

32、only employed microstrip antenna is a rectangular patch. The rectangular patch antenna is approximately a one-half wavelength long section of rectangular microstrip transmission line. When air is the antenna substrate, the length of the rectangular microstrip antenna is approximately one-half of a f

33、ree-space wavelength. 最普遍应用(yngyng)的微带天线是矩形贴片。矩形贴片天线长近似为矩形微带传输线的一段，其长度等于半波长。当空气作为天线基底时，矩形微带天线的长度大约为自由空间波长的一半。Unit 3-2 微带天线共六十七页26Since the antenna is loaded with a dielectric as its substrate, the length of the antenna decreases as the relative dielectric constant of the substrate increases. The res

34、onant length of the antenna is slightly shorter because of the extended electric “fringing fields” which increase the electrical length of the antenna slightly. 因为天线是负载绝缘体作为它的基底，所以天线的长度会随着基底的相对介电常数的增加而减小。天线的谐振长度略短一些，这是因为“边缘(binyun)场”稍微增加了天线的电气长度。Unit 3-2 微带天线Fringing fields: the electric fields prod

35、uced by scattered electrons in an electron microscope.共六十七页27An early model of the microstrip antenna is a section of microstrip transmission line with equivalent loads on either end to represent the radiation loss.微带天线的一个早期模型是一段微带传输线，在一端(ydun)具有等效负载，代表辐射损耗。Unit 3-2 微带天线共六十七页28The dielectric loading

36、 of a microstrip antenna affects both its radiation pattern and impedance bandwidth. As the dielectric constant of the substrate increases, the antenna bandwidth decreases which increases the Q factor of the antenna and therefore decreases the impedance bandwidth.3 微带天线的介电负载影响(yngxing)天线的辐射模式和阻抗带宽。随

37、着基底介电常数的增大，天线的带宽减小，其Q值提高，因而阻抗带宽减小。Unit 3-2 微带天线共六十七页29This relationship did not immediately follow when using the transmission line model of the antenna, but is apparent when using the cavity model which was introduced in the late 1970s. The radiation from a rectangular microstrip antenna may be und

38、erstood as a pair of equivalent slots. 当使用天线的传输线模型(mxng)时这种情况并没有发生，到了七十年代后期出现空腔模型(mxng)时这种情况就显现出来了。Unit 3-2 微带天线共六十七页30These slots act as an array and have the highest directivity when the antenna has an air dielectric and decreases as the antenna is loaded by material with increasing relative diele

39、ctric constant.矩形(jxng)微带天线的辐射可以理解为一对等效的狭缝。这些狭缝就像一个阵列，当天线使用空气电介质时方向性最好，但是当天线的负载材料的相对介电常数增加时方向性会减弱。Unit 3-2 微带天线共六十七页31An advantage inherent to patch antennas is the ability to have polarization diversity. Patch antennas can easily be designed to have various polarizations, using multiple feed points

40、, or a single feed point with asymmetric patch structures.4 This unique property allows patch antennas to be used in many types of communications links that may have varied requirements. 贴片天线固有的优点是能有极化分集。片状天线能很容易地通过多个馈点或在非对称片结构上采用单一馈点设计(shj)成具有各种极化特性。这个独特的性质使得贴片天线应用于有不同需求的通信链接的许多领域。Unit 3-2 微带天线共六十七

41、页32The half-wave rectangular microstrip antenna has a virtual shorting plane along its center. This may be replaced with a physical shoring plane to create a quarter-wavelength microstrip antenna. This is sometimes called a half-patch. 半波矩形微带天线沿其中心有一个虚拟短路平面。用物理短路平面替代上述(shngsh)虚拟短路平面就可以做成四分之一波长微带天线。有

42、时称四分之一波长微带天线为半贴片。Unit 3-2 微带天线共六十七页33The antenna only has a single radiation edge (equivalent slot) which lowers the directivity/gain of the antenna. The impedance bandwidth is slightly lower than a half-wavelength full patch as the coupling between radiating edges has been eliminated.这种天线只有(zhyu)单一

43、的辐射边缘（等效狭缝），因此会降低天线的方向性/增益。由于没有辐射边缘之间的耦合，所以阻抗带宽也比半波长全贴片窄。Unit 3-2 微带天线共六十七页34Unit 3 电磁场, 天线(tinxin)和微波EM Fields, Antenna and MicrowavesUnit 3-3 微波(wib)Microwaves共六十七页35New Wordsterahertz 特赫，1012赫兹boundary 边界，分界线infrared 红外线apparatus 设备，装置，仪器lumped element集总元件opaque 不透（明）的transparent 透明的，可透过的vacuum t

44、ube 真空管，电子管ballistic motion 冲击运动magnetron 磁电管，磁控管klystron 速调管traveling wave tube 行波管gyrotron 振动陀螺仪clump 簇，团dipole 偶极子moment 矩friction 摩擦，摩擦力resonance 谐振，共振convection 对流penetrate 穿透，渗透共六十七页36New Wordsdeposit 存放，堆积antenna 天线van 货车，篷车advent 到来multiplex 复用bluetooth 蓝牙metropolitan 都市的interoperability 互操作

45、性coax cable 同轴电缆plasma 等离子体reactive ion etching 反应离子刻蚀vapor deposition 汽相淀积，蒸镀beam 发送，传送，光束maser 迈泽radio astronomy 射电天文学共六十七页37Microwaves are electromagnetic waves with wavelengths longer than those of terahertz (THz) frequencies, but relatively short for radio waves. Microwaves have wavelengths app

46、roximately in the range of 30cm (frequency = 1GHz) to 1mm (300GHz). This range of wavelengths has led many to question the naming convention used for microwaves as the name suggests a micrometer wavelength.1 微波是波长比频率为特赫兹(hz)（THz）的波更长，但比无线电波短的电磁波。微波的波长范围大约在30厘米（频率= 1 GHz ）到1毫米（ 300 GHz）之间。这个波长范围已经使人对

47、命名习惯提出了问题，因为微波使人联想到微米波长。Unit 3-3 微波(wib)共六十七页38However, the boundaries between far infrared light, terahertz radiation, microwaves, and ultra-high-frequency radio waves are fairly arbitrary and are used variously between different fields of study. The same equations of electromagnetic theory apply a

48、t all frequencies. 然而，远红外光，赫特辐射，微波，超高频无线电波(wxin dinb)之间的界限相当随意的，在不同的学科领域有不同的用法。电磁理论的同一个方程组应用于所有频率。Unit 3-3 微波(wib)共六十七页39Apparatus and techniques may be described as “microwave” when the wavelengths of signals are roughly the same as the dimensions of the equipment, so that lumped-element circuit th

49、eory is no longer accurate. 当信号的波长(bchng)和设备的尺寸大致相同时，仪器和技术可被描述为“微波”，因此集总元件电路理论不再准确。Unit 3-3 微波(wib)共六十七页40The term microwave generally refers to “alternating current signals with frequencies between 300MHz (3108Hz) and 300GHz (31011Hz).” However, both IEC standard 60050 and IEEE standard 100 define

50、“microwave” frequencies starting at 1 GHz (30 cm wavelength).微波这个术语一般是指“频率为300 MHz和300GHz之间的交流电信号” 。但是，IEC标准60050和IEEE标准100都定义“微波”频率从1 GHz（ 30厘米(l m)波长）开始。Unit 3-3 微波(wib)共六十七页41The existence of electromagnetic waves, of which microwaves are part of the frequency spectrum, was predicted by James Cle

51、rk Maxwell in 1864 from his equations. In 1888, Heinrich Hertz was the first to demonstrate the existence of electromagnetic waves by building an apparatus that produced and detected microwaves in the UHF region. 詹姆斯克拉克麦克斯韦于1864年根据(gnj)他的方程组预言了电磁波存在，而微波只是电磁波频谱中的一部分。 1888年，亨利希赫兹构建了在UHF频段产生和检测微波的装置，首次

52、证明了电磁波的存在。Unit 3-3 微波(wib)共六十七页42In 1894 J. C. Bose publicly demonstrated radio control of a bell using millimeter wavelengths, and conducted research into the propagation of microwaves. The microwave range includes ultra-high frequency (UHF) (0.33GHz), super high frequency (SHF) (330GHz), and extre

53、mely high frequency (EHF) (30300GHz) signals. 1894 J. C. Bose公开展示了用毫米波长(bchng)对钟进行的无线电控制，并引导了微波传播的研究。微波范围包括超高频（UHF）（0.3-3 GHz），甚高频（SHF）（3-30GHz）以及极高频(EHF）（30-300 GHz）信号。Unit 3-3 微波(wib)共六十七页43Above 300GHz, the absorption of electromagnetic radiation by Earths atmosphere is so great that it is effect

54、ively opaque, until the atmosphere becomes transparent again in the so-called infrared and optical window frequency ranges. 地球(dqi)大气对高于300 GHz的电磁辐射的吸收是如此之大，以至于变得实际上是不透明，直到所谓的红外线和可见光窗口的频率范围，大气又变得透明。Unit 3-3 微波(wib)共六十七页44Vacuum tube based devices operate on the ballistic motion of electrons in a vac

55、uum under the influence of controlling electric or magnetic fields, and include the magnetron, klystron, traveling wave tube (TWT), and gyrotron.2基于电子管的器件是在受控制电场和磁场影响(yngxing)的真空内由电子的冲击运动而工作的，包括磁控管，速调管，行波管和振动陀螺仪。Unit 3-3 微波(wib)器件共六十七页45These devices work in the density modulated mode, rather than t

56、he current modulated mode. This means that they work on the basis of clumps of electrons flying ballistically through them, rather than using a continuous stream.3这些(zhxi)器件工作在密度调制模式而不是电流调制方式。这意味着它们是基于真空管发出的电子簇工作的，而不是用连续的电子流。Unit 3-3 微波(wib)器件共六十七页46A microwave oven works by passing microwave radiat

57、ion, usually at a frequency of 2450MHz (a wavelength of 12.24cm), through the food. Water, fat, and sugar molecules in the food absorb energy from the microwave beam in a process called dielectric heating. 微波炉是通过穿过食物的微波辐射工作的，通常频率是在2450 MHz（波长12.24厘米(l m)）。食物中的水、脂肪和糖分子在称为电介电加热的过程吸收微波波束的能量。Unit 3-3 微波

58、(wib)用途共六十七页47Many molecules (such as those of water) are electric dipoles, meaning that they have a positive charge at one end and a negative charge at the other, and therefore rotate as they try to align themselves with the alternating electric field induced by the microwave beam. 许多分子（如那些水）是电偶极子，

59、这意味着它们一端带正电，另一端带负电(fdin)，因此它们力图与微波波束所引起的交变电场保持一致而发生旋转。Unit 3-3 微波(wib)用途共六十七页48This molecular movement creates heat as the rotating molecules hit other molecules and put them into motion. Microwave heating is most efficient on liquid water, and much less so on fats and sugars (which have less molecu

60、lar dipole moment), and frozen water (where the molecules are not free to rotate). 旋转分子撞击其它分子使他们运动，这种分子运动产生热量(rling)。微波加热对液态水是最有效的，其次为脂肪和糖类（分子偶极矩较少）以及冷冻水（分子不能自由转动）。Unit 3-3 微波(wib)用途共六十七页49Microwave heating is sometimes incorrectly explained as a rotational resonance of water molecules: such resonan