电子工程专业外语考试题

电子工程专业外语考试题
1.The advantages of the transistor over the vacuum tube wereenormous. Compared totheold technology ,transistors were much smaller ,faster ,and cheaper to manufacture . They were also far more reliable and used much less power . The transistor is what started the evolution of the modern computer industry in motion. 和真空管相比，晶体管存在着巨大优势：晶体管的尺寸小得多，切换速度快得多，生产成本低得多；晶体管的性能更加可靠，耗能也更少。

晶体管的发明带来了计算机工业的蓬勃发展。

2. A special material is used to make these integrated circuits. While most materials either insulate from electrical flow (air , glass ,wood )or conduct electricity readily (metals ,water ), there are some that only conduct electricity a small amount ,or only under certain conditions . These are called semiconductors . the most commonly used semiconductor is of course silicon .
制造集成电路需要使用一类特殊材料。

多数材料要么对电流绝缘（如空气，玻璃，木头），要么很容易传导电流（如金属，水溶液），但也有一些材料只能传到少量电流，或只在特定条件下传导电流------这种材料被称作“半导体”。

硅是最常用的半导体材料。

3. A flip-flop is basically a bi-state circuit in which either a 0 or 1 state can resides. beacause its simplicity ,the flip-flop is extremely fast . as a basic element , the flip-flop is used in digital circuits and Ics .
A flip-flop will lose its state
when the supply votage is
removed.Therefore,itis volatile.
触发器是一种存储“0"或”1“的
双态电路。

由于结构简单，所
以触发器速度极快。

触发器是数
字电路和集成电路的基础构件。

由于电源电压去掉后，触发器的原有状态就失去了，因此触发器是易失的.
4.RAM standsforrandom-ac cess memory . RAM contains bytes of information , and the microprocessor can read or write to those bytes depending on whether the RD or WR line is signaled . One problem with today’s RAM chips is that they forget everything once the power goer off . that is why the computer needs ROM .
RAM 是随机存取存储器。

RAM 中包含着以字节为单位的信息，微处理器能够依据RD/WR 信
号哪个有效来决定字节的读、写。

当前RAM芯片的一个问题是，掉电后，所有保存在RAM
上的内容全部丢失。

这就是计算机需要ROM 的原因。

5.The test register is a
special latch that can hold values from comparisons performed in the ALU . An ALU can normally compare two numbers and determine if they are epual , if one is greater
than the other , etc. The test register can also normally hold a carry bit from the last stage of the adder . It stores these values in flip-flops and then the instrucion decoder can use the values to make decisions.
测试寄存器；一种保存ALU比
较结果的专用锁存器。

通常，ALU能够将两个数进行比较，
并判断出二者是否相等或者哪
个更大。

测试寄存器也可以保存加法运算最后一步的进位位。

这些数值保存在处罚期当中，指令译码器利用这些数值作出判决。

6.It is extremely hard to define dynamic range (DR) for an op amp, so let’s start with a digital-to-analog converter (DAC)where DR is defined as the ratio of the maximum output voltage to the smallest output voltage the DAC can produce .
由于很难定义运算放大器的”动态范围“，因此先给”数模转换器“的动态范围下定义。

DAC
的动态范围就是其最大输出电
压和最小输出电压之比。

7.The switching regulator
operates the power devices in
the full-on and cutoff states.
This then results in either large
currents passed through the
power devices with a low on
voltage or no current flowing
with high voltage across the
devece . This results in a much
lower power being dissipated
within the supply. The average
switching power supply
exhibits efficiencies of between
70 to 90 percent,regardless of
the input voltage .
开关电源中的功率器件工作在”
全开“和”截断“状态。

这样，
要么在大电流流经功率器件时，
导通电压很低；要么在大电压
时，没有电流通过器件。

因此，
电源内部消耗的功率就很少。

开
关电源的平均效率为70%-90%，
而且和输入电压无关。

8.Frequency synthesizers
use one or more Phase-Locked
Loops (PLL) to generate one to
many different frequencies on their outputs, from one or more referencesources.The reference frequency is usually generated by a crystal attached to the synthesizer. The design goal of frequency synthesizers is to replace multiple oscillators in a system, and hence reduce board space and cost.
通过使用一个或多个”锁相环“，频率合成器从一个或多个参考时钟源产生一个或多个不同的输出频率。

参考频率通常是由连接到合成器上的晶体产生的。

设计频率合成器的目的是用以替代系统中的多个振荡器，从而减少了电路板空间，降低了系统成本。

9. A block buffer is a device in which th output waveform directly follows the input waveform. The input wavefom propagates through the device and is redriven by the output buffers. hence, such devices have a propagation delay associated with them .In addition ,due to the differences between the propagation delay through the device on each input-output path ,skew will exist on the outputs .
时钟缓冲器是一种输出波形直接跟随输入波形的器件。

输入波形通过该器件并被输出缓冲器重新驱动。

因此，该类器件存在传输延迟。

此外，由于在每个输入，输出通道间存在传输延迟的差别，输出端将出现相位抖动10. A resistor at high frequency acts like a series combination of inductance with the resistor in parallel with a capacitor. A capacitor at high frequency acts like an inductor and resistor in series
combination with the capacitor
plates .
工作在高频的电阻表现为电感
和并联的电阻，电容之间的级
联。

工作在高频的电容表现为电
感，电阻和电容的级联。

11.In an area where the
number of users has grown to
the point that the system is
overloaded , the poer is
reduced , and the overloaded
cells are split int smller
microcells to permit more frequency reuuse. Telephone companies sometimes create temporary microcells, using portable towers with satellite links at sporting events , rock concerts , and other places where large numbers of mobile users congregate for a few hours .
在用户数量达到导致系统过载
程度的地区，为了实现更多的频率重用，需要降低功率并过载蜂窝小区分为更小的微蜂窝单元。

在体育赛事，摇滚音乐会及其他在几个小时内有大量移动用户
云集的场所，电话公司有时会使用卫星链接的便携发射塔创建
临时'微蜂窝”。

12.CDMA is completely different from AMPS.
D-AMPS, and GSM .instead of dividing the allowed frequency range into a few hundred narrow channels , CDMA allows each station to transmit over the entire frequency spectrum all the time .multiple simultaneous transmissions are separated using coding theory .
CDMA also relaxes the assumption that colliding frames are totally garbled. instead, it assumes that multiple signals add linearly . CDMA和AMPS ,D-AMPS 及GSM完全不同。

CDMA没有将可用频带分割为几百个窄带信道，而是允许信号在整个频谱范围内传送。

利用编码原理，CDMA可以将多个同时传送的信号分离开来。

在CDMA中，“相
遇数据帧会造成数据混淆”的想法不存在了--CDMA认为多路信号之间是线性相加的。

13. A base station communicates with mobiles using two types of radio channels, control channels to carry control information and traffic channels to carry messages .
基站使用两类无线信道和移动用户进行通信：传送控制信息的“控制信道”和传送消息的”通信信道“
14.In an FDMA scheme the available spectrum is divided into a number of frequency
channels of certain bandwidth
and individual calls use ifferent
frequency channels. all
first-generation cellular
systems use this scheme .
在FDMA方式中，可用频谱划
分为若干具有一定带宽的频道；
每个呼叫都使用不同频道。

第一
代蜂窝系统采用的都是FDMA
方式。

15.Some digital logic Ics
and their analog counterparts
(analog/digital converters, for
example ) are standard parts ,
or standard Ics . you can
select standard Ics from
catalogs and data books and
buy them from distributors .
systems manufacturers and
designers can use the same
standard part in a variety of different microelectronic systems (systems that use microelectronics or Ics)
有些数字逻辑集成电路和模拟集成电路（如模数转换器）是标准器件或者标准集成电路。

可以从产品目录和数据手册当中选择标准集成电路，从经销商处购买。

系统制造商和设计人员可以在各种不同的微电子系统（”微电子系统“是指应用微电子技术和集成电路的系统）中使用相同的标准的器件。

16. A hard core is a block of logic for a particular function on
a chip that is designed at the circuit level. microprocessors are typically hard cores , which ties them to a particular foundry’s
semiconductor process .microcontrollers or systems on a chip (socs) may be entirely hard cores or made up of hard (hardwired) cores and soft (programmable) cores .
硬核是一种在芯片电路级设计的，具有特定功能的逻辑模块。

微处理器就是典型的硬核，微处理器和特定芯片制造商的半导体生产工艺是联系在一起的。

微控器或片上系统可能全部都是硬核，也可能是由硬核和软核组合而成。

17.After a brief acquisition time , during which a sample is acquired , the sample and hold circuit holds the sample steady for the remainder of the sampling interval . this hold time is needed to allow time for an A/D converter to generate a digital code that best corresponds to the analog sample . 经过一段短暂的采集时间之后
（其间采集到一个样本），采样
保持电路将这个样本一直保持
到下一个采样间隔的开始。

A/D
转换器需要利用这个保持时间
生成模拟样本对应的码字。

18.DSPs are available in two
major classes : fixed point and
floating point . the fixed point
class represents real numbers in
a fixed number of bits . the
position of the binary point
(similar to the decimal point)
can be controlled by the
programmer , and determines
the range of numbers that can
be represented . as the range
increases , though , the
available precision goes down , since fewer bits lie to the right og th binary point .
DSPs 分为定点和浮点两大类。

定点DSPs使用固定的比特数来
代表实数。

二进制小数点的位置
可以由编程人员决定，这个位置
决定了可以表示的实数范围。

可
用精度会随着表示范围的增加
而下降，因为二进制小数点右边
的比特数减少了。

19.Floating point DSPs represent real numbers using a mantissa and exponent, similar to scientific notation: many combine mantissa and exponent into a 32-bit number . the dynamic range for floating point fevices is calculated from the largest and smllest multipliers , where E is the exponent . thus , for a representation that uses 24 bits for the mantissa and 8 bits for the signed exponent , the dynamic range is 20log
=1535.3 dB. A large dynamic range means the system has great power to represent a wide range of input signals , from
very small to very large .
浮点DSPs使用”尾数”和“指数”来表示实数，这种方法很像
科学计数法----将尾数和指数组
合成一个32位数。

浮点器件的
动态范围是用的最大值和最小
值进行计算的，此处E是指数。

对于24位尾数和8位有符号指
数的表示方法而言，动态范围
是。

大的动态范围意味着系统具
备更大的表示很宽范围输入信
号的能力，从很小的信号到很大
的信号。

20.The primary reason for processing real-world signals
is to extract information from them. this information normaly exists in the form of signal amplitude (absolute or relative ), frequency or spectral content , phase , or timing relationships with respect to other signas . once the desired information is extracted from the signal , it may be used in a number of ways .
“提取信息”是对现实世界信号进行处理的主要原因。

通常，信息的存在形式是信号幅度（绝对幅度或相对幅度），频率（或频谱成分），
相位（或者和其他信号之间的时序
关系）。

一旦把有用信息从信号中提
取出来，就能以多种方式使用这些
信息。

21.In addition to EFM, the
data are encoded in a format
called two-level
Reed-Solomon coding . this
involves combining the left and
right stereo channels along
with data for error detection
and correction . digital errors
detected during playback are
either ; corrected by using the
redundant data in the encoding scheme , concealed by interpolating between adjacent samples , or muted by setting the sample value to zero . these encoding schemes results in the data rate being triples , i.e ., 1.4 mbites /sec for the stereo audio signals versus 4.3 mbits /sec stored on the disc .
除了EFM之外，数据以二级“里德-所罗蒙编码”方式进行编码。

这种编码方法对左，右声道和检错，纠错数据进行组合。

播放时检测到的错误，可以使用编码机制中的冗余数据进行纠正，也可以用临近样本插值的方法去除，还可以用“样本置零”的方法使之“静音”。

这些编码机制使得数据率增至原来的三倍-即1.4mbps的立体声音频信号将以4.3mbps的数据率存储在光盘上。

22.Audio compression can be done in one of two ways. in waveform coding the signal is transfomed mathematically by a fourier transform into its frequency components . the amplitude of each component is then encoded in a minimal way . the goal is to reproduce the waveform accurately at the other end in as
few bits as possible .
音频压缩可以通过两种方式实现。

在“波形编码”中，用“傅里叶变换”这种数学方法将波形信号变换为频率分量。

每个分量的幅度采用最小方式进行编码，目的是用尽可能少的比特数在另一端准确重现波形。

另外一种方法就是“知觉编码”。

这种方法利用了人类听觉系统的缺陷，采用让人耳听不出来差别的方式对信号进行编码，尽管在示波器上观看重放波形差别很大。

知觉编码技术是建立在“心理声学”基础之上的。

'心理声学“研究的是人类感知声音的方式。

而MP3建立在知觉编码基础之上。

/doc/fdb8608671fe910ef12df8d0.htm l panding can be carried out in three ways :(1) run the analog signal through a nonlinear ircuit before reaching a linear 8 bit ADC , (2) use an 8bit ADC that internally has unequally spaced steps , or (3) use a linear 12bit ADC followed by a digital look-up table (12bits in ,8 bits out ) . each of these three options requires the same onlinearity , just in a different place : an analog circuit , an ADC , or a digital circuit .
压扩的实现方法有三种：（1）先用非线性电路对模拟信号进行处理，然后输出到8位线性ADC。

（2）使用内部采用非均匀量化间隔的8位ADC。

（3）使用12位线性ADC，之后使用一张”12位进-8位出“的数字查找表。

这三种方法所需的非线性处理是一样的，只不过这种非线性处理出现在不同的地方；模拟电路中，ADC或者数字电路。