专业英语考试复习

考试涉及的课后Notes 内容

1. The output of the differential amplifier is fed to the circuit’s output stage via an offset-compensation

network, which causes the op-amp’s output to center at zero volts. The output stage takes the form of a complementary emitter follower, and provides a low-impedance output.差动放大级的输出通过一个失调补偿网络与输出级相连, 目的是使运放的输出以0 V 为中心。 输出级采用互补的射极 跟随器的形式以使输出阻抗很低。

2. Because of the very high open-loop voltage gain of the op-amp, the output is driven into positive

saturation (close to +V) when the sample voltage goes slightly above the reference voltage, and driven into negative saturation (close to-V) when the sample voltage goes slightly below the reference voltage.由于运放的开环电压增益很高, 当取样电压略高于参考 电压时, 输出趋向于正向饱和状态(接近+V)。 当取样电压低 于参考电压时, 输出趋向于负向饱和状态(接近-V) 。

3. The fundamental purpose of an electronic communication system is to transfer information from one

place to another.电子通信系统的基本作用是把信息从此地传送到彼地。

4. The original source information can be in analog (continuous) form, such as the human voice or

music, or in digital (discrete) form, such as binary-coded numbers or alphanumeric codes.原始的信息源既可以是模拟(连续) 的, 例如语音或音乐; 也可以是数字(离散) 的, 例如二进制编码数或字符码。

5. Digital transmission system-embodied by telegraph systems-were developed in the 1850s before

analog systems-the telephone-in the twentieth century.以电报为代表的数字传输系统研发于19世纪

50年代, 早 于以电话为代表的模拟系统, 它是20世纪才开发的。

6. The signal-processing block at the transmitter conditions the source for more efficient transmission.

发射机中的信号处理单元对信源进行调理, 以便更有效 地传送。

7. In addition, the signal processor may also add parity bits to the digital word to provide channel

coding so that error detection and correction can be used by the signal processor in the receiver to reduce or eliminate bit errors that are caused by noise in the channel.此外, 信号处理器还可以给数码字加入奇偶校验位, 即提 供信道编码, 使得接收机的信号处理器可以进行误码检测和 纠错, 以减少或消除由信道噪声所引起的误码。

8. In digital communication systems, the modulating signal (e. g., message) may be represented as a

time sequence of symbols or pulses, where each symbol has mfinite states. Each symbol represents nbits of information, where n=log2m bits/symbol.在数字通信系统中, 调制信号(比如消息) 用符号或者脉冲 的时间序列来表示, 每一个符号有m 个有限状态。 每个符号 表示n 比特的信息, 这里n ＝log2m 比特/符号。

9. The power efficiency, ηp (sometimes called energy efficiency) of a digital modulation scheme is a

measure of how favorably this tradeoff between fidelity and signal power is made, and is often expressed as the ratio of the signal energy per bit to noise power spectral density (Eb/No) required at the receiver input for a certain probability of error (say 10-5).数字调制方法的功率效率ηp(有时也称为能量效率) 用来衡 量精确度和信号功率之间平衡的好坏程度, 通常以接收机的输 入满足给定误码率

(比如10-5) 时, 单位比特信号能量与噪声的 功率谱密度之间的比值(Eb/No)来表示功率效率。

10. Depending on the relationship between the signal frequencies and the sampling rate, spectral

inversion may cause the shape of the spectrum in the baseband to be inverted from the true spectrum of the signal.根据信号频率和采样频率之间的关系的不同, 可能出现 “频谱反转”现象——基带频谱的形状和信号真实频谱的形 状正好相反。

11. If a universal microprocessor solution existed with which every design could realized, the electronics

industry wouldn’t be a very competitive place.假如存在可用以实现任何设计的通用微处理器的话, 电 子行业就不会竞争得如此激烈了。

12. As such, every new version of the product requires a redesign and trips through the foundry, an

expensive proposition, and an impediment to rapid time-to-market.而且, 每次推出一个新产品都需要重新设计并经历所有 制造流程。 这样做不但造价昂贵, 而且不利于迅速上市。· time-to-market 的意思为“上市时间”。

13. However, for applications in which the end product must process answers in real time, or must do so

while powered by consumer batteries, GPPs comparatively poor real time performance and high power consumption all but rules them out. 然而, 在最终产品必须实时响应的应用中, 或者必须在 电池供电下实现实时响应的应用中, 由于GPP 实时性能较差、 功耗大， 因此就被排除在外了。

14. Intensity is a measure of power per unit area, and even a laser that emits only a few milli-watts can

produce a lot of intensity in a beam that’s only a millimeter in diameter. 强度是每单位面积上能量的度量，即使一个仅产生几毫 瓦能量的激光器也能产生一个直径只有1毫米的高强度光束。

15. Laser beams have been produced in every color of the rainbow (red is the most common laser color),

as well as in many kinds of invisible light, but each laser can emit one color and one color only.激光束可以是彩虹中的每一种颜色(红色是最常见的激 光颜色), 还可以是许多种看不见的光, 但每个激光器能且只 能发出一种颜色的光。

16. This network could enhance communications between teachers and staff, allowing students to gain

more of their teacher’s time for instruction, personal attention, and an enriched curriculum. 这个网络可以加强教职员之间的交流，使得老师们有更多的时间用来给学生们授课、个别辅导，以及开更多的课程。

17. Furthermore, this information would be a vailable to the patient’s private physician and to this (or

another) hospital in case of a subsequent readmission or transfer to another facility. 而且，万一以后重进医院或转入其他地方，病人的私人 大夫和这家（或其他）医院都可以看到这些信息资料。

18. The capabilities mentioned in the paragraphs above are all possible; it remains only for the

applications and products to be designed to take advantage of this communications technology. 以上各段提到的功能都是可能的，所剩下的只是更好地 运用通信技术来设计产品并应用它们。

19. When an image uses only a small portion of the available gray scale levels, histogram equalization

can be used to spread out the usage of gray scale levels over the entire available range.当一幅图像

只使用了可用灰度级的一小部分时, 可以使 用直方图均衡的方法将灰度级的使用扩展到整个可用的范围。

20. Low pass filters blur images, high pass filters emphasize sharp changes in gray scale level, and

edge filters locate edges in an image． 低通滤波器使图像变得模糊, 而高通滤波器突出了图像 的灰度锐变, 边缘滤波器则对图像边缘进行定位。

21. The phase spectrum carries the best information about the locations of the objects in the image．相

位谱携带着图像中目标位置的信息。

22. CT scans are X-rays taken in many directions in a single plane of an object.CT技术是使用X 射线从

不同方向对目标的某个平面进行 扫描。

23. Lossless compression means that a file is compacted without losing any information, so that the

reconstructed file is identical to the original．无损压缩是不损失任何信息地将文件进行压缩, 重建得 到的文件和原文件是完全一样的。

24. JPEG, an extremely common image compression scheme, uses the discrete cosine transform (DCT)

to concentrate most of the information about an 17×17 sub-block of an image into a few significant coefficients.JPEG 是一种极其常用的图像压缩方法, 该方法使用离散 余弦变换将图像中17×17小块的大部分信息集中到少数几个 重要系数上。

25. How we obtain news and entertainment, conduct business and education, and accomplish

scientific and technical research will all be affected.我们获得新闻和娱乐、 处理事务和进行教育以及完成科 学研究的方式将全部受到影响。

26. Networks can be analog, in which information is represented by continuous smoothly varying signals,

or digital, in which information is represented by discrete on/off signals.网络可以是模拟的, 其中信息以连续平稳变化的信号表示; 也 可以是数字的, 其中信息以离散的有/无信号表示。

27. As these networks have grown in popularity, they have begun to interconnect, creating a global

collection of people and computers that are able to electronically communicate with one another.由于这些网络渐渐普及, 它们已开始互联, 创建了一种 全球性的人机集合, 使他们彼此间可以进行电子化通信。

28. An example you may be familiar with is the cellular telephone network, which is made possible by

dividing a geographical area into hexagonal-shaped cells, each with a base station.你可能熟知的一个例子是蜂窝式电话网, 其构成通常是 把一块地理区域划分为若干六边形的单元, 每个单元具有一个基站。

29. On a bus network computers are simply connected by a cable routed along a path in the vicinity of

each device that must be connected to it.在总线形网络上, 计算机由一根电缆简单地连接, 电缆的 路由是按附近每个必须连接到电缆上的设备的路径而定的。

30. As the satellite received a signal from a ground or earth station, a communications complex that

transmitted and/or received satellite signals, it relayed its own signal to earth.当卫星接收了从地面或地球站发来的信号后， 卫星上 的通信设备将要发送的和（或）已接收的卫星信号复合起来 后再发往地球。

31. Today’ communications satellites, for the most part, have followed suit and are placed in what are

called geostationary orbital positions or “slots”.对于当今的通信卫星, 绝大部分都遵循此道, 放置在被称 之为相对地面静止轨道的位置上。