通讯工程方面的文献翻译

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1、译文： Electronics is the study of the flow of charge through various materials and devices such as semiconductors, resistors, inductors, capacitors, nano-structures and vacuum tubes. Although considered to be a theoretical branch of physics, the design and construction of electronic circuits to solve

2、practical problems is an essential technique in the fields of electronic engineering and computer engineering. This science starts about 1908 with the invention by Dr Lee De Forest of the valve (triode) Before 1950 this science was named Radio or Radio technics because that was its principal applica

3、tion. The study of new semiconductor devices and surrounding technology is sometimes considered a branch of physics. This article focuses on engineering aspects of electronics. Electronic systems are used to perform a wide variety of tasks. The main uses of electronic circuits are: The controlling a

4、nd processing of data. The conversion to/from and distribution of electric power. Both these applications involve the creation and/or detection of electromagnetic fields and electric currents. While electrical energy had been used for some time prior to the late 19th century to transmit data over te

5、legraph and telephone lines, development in electronics grew exponentially after the advent of radio. One way of looking at an electronic system is to divide it into 3 parts: Inputs Electronic or mechanical sensors (or transducers). These devices take signals/information from external sources in the

6、 physical world (such as antennas or technology networks) and convert those signals/information into current/voltage or digital (high/low) signals within the system. Signal processors These circuits serve to manipulate, interpret and transform inputted signals in order to make them useful for a desi

7、red application. Recently, complex signal processing has been accomplished with the use of Digital Signal Processors. Outputs Actuators or other devices (such as transducers) that transform current/voltage signals back into useful physical form (e.g., by accomplishing a physical task such as rotatin

8、g an electric motor). For example, a television set contains these 3 parts. The televisions input transforms a broadcast signal (received by an antenna or fed in through a cable) into a current/voltage signal that can be used by the device. Signal processing circuits inside the television extract in

9、formation from this signal that dictates brightness, colour and sound level. Output devices then convert this information back into physical form. A cathode ray tube transforms electronic signals into a visible image on the screen. Magnet-driven speakers convert signals into audible sound. Electroni

10、c devices and components An electronic component is any physical entity in an electronic system whose intention is to affect the electrons or their associated fields in a desired manner consistent with the intended function of the electronic system. Components are generally intended to be in mutual

11、electromechanical contact, usually by being soldered to a printed circuit board (PCB), to create an electronic circuit with a particular function (for example an amplifier, radio receiver, or oscillator). Components may be packaged singly or in more or less complex groups as integrated circuits. Typ

12、es of circuits Analog circuits Most analog electronic appliances, such as radio receivers, are constructed from combinations of a few types of basic circuits. Analog circuits use a continuous range of voltage as opposed to discrete levels as in digital circuits. The number of different analog circui

13、ts so far devised is huge, especially because a circuit can be defined as anything from a single component, to systems containing thousands of components. Analog circuits are sometimes called linear circuits although many non-linear effects are used in analog circuits such as mixers, modulators, etc

14、. Good examples of analog circuits include vacuum tube and transistor amplifiers, operational amplifiers and oscillators. Some analog circuitry these days may use digital or even microprocessor techniques to improve upon the basic performance of the circuit. This type of circuit is usually called mi

15、xed signal. Sometimes it may be difficult to differentiate between analog and digital circuits as they have elements of both linear and non-linear operation. An example is the comparator which takes in a continuous range of voltage but puts out only one of two levels as in a digital circuit. Similar

16、ly, an overdriven transistor amplifier can take on the characteristics of a controlled switch having essentially two levels of output. Digital circuits Main article: Digital circuits Digital circuits are electric circuits based on a number of discrete voltage levels. Digital circuits are the most co

17、mmon physical representation of Boolean algebra and are the basis of all digital computers. To most engineers, the terms digital circuit, digital system and logic are interchangeable in the context of digital circuits. In most cases the number of different states of a node is two, represented by two

18、 voltage levels labeled Low(0) and High(1). Often Low will be near zero volts and High will be at a higher level depending on the supply voltage in use. Computers, electronic clocks, and programmable logic controllers (used to control industrial processes) are constructed of digital circuits. Digital Signal Processors are another example. Building-blocks: Logic gates Adders Binary Multipliers Flip-Flops Counters Registers Multiplexers Schmitt triggers Highly integrated devices: Microprocessors