1、中文 2040 字 Introduction to Communication System It is often said that we are living in the information age. Communication technology is absolutely vital to the generation, storage, and transmission of this information. Any communication system moves information from a source to a destination through
2、a channel. Figure 1 illustrates this very simple idea. The information from the source will generally not be in a form that can travel through the channel, so a device called a transmitter will be employed at one end and a receiver at the other. Figure 1 simple communication system The source or inf
3、ormation signal can be analog or digital. Common examples are analog audio, video signals and digital data. Sources are often described in terms of the frequency range that they occupy. Telephone-quality analog voice signals, for instance, contain frequencies from 300Hz to 3kHz, while analog high-fi
4、delity music needs a frequency range of approximately 20Hz to 20kHz. Digital sources can be derived from audio or video signals can have almost any bandwidth depending on the number of bits transmitted per second, and the method used to convert binary ones and zeros into electrical signals. A commun
5、ication channel can be almost anything: a pair of conductors, an optical fiber or a free space that we live. Sometimes a channel can carry the information signal directly. For example, an audio signal can be carried directly by a twisted-pair telephone cable. On the other hand, a radio link through
6、free space cannot be used directly for voice signals. Such situation require the use of a carrier wave will be altered, or modulated m, by the information signals in such a way that the information can be recovered at the destination. When a carrier is used, the information signal is also known as t
7、he modulating signals. Technology is at the core of many new and emerging digital information products and applications that support the information society. Such products and applications often require the collection, sometimes in real time. The ability of technology to handle real world signals di
8、gitally has made it possible to create affordable, innovative； and high quality products and applications for large consumer market for example: digital cellular mobile phone, digital television and video games. The impact of is also evident in many other areas, such as medicine and healthcare. For
9、example: in patient monitors for intensive care, digital X-ray appliances, advanced cardiology and brain mapping systems and so on, digital audio, for example: CD players； audio mixers and electronic music and so on. And personal computer systems for example: disks for efficient data storage and err
10、or correction, moderns, sound cards and video conferencing and so on. Most of the major cities in the domestic bus stop artificial voice. Every one of the key points from the driver or attendant to stop by voice. But sometimes due to various factors such as weather, vehicle congestion, Source Transm
11、itter Receiver Destination flight attendants are feeling the effects of the changes. There being given the stations reporting stations, especially for passengers not familiar with the topography of the city, causing a lot of unnecessary trouble. Well thus affect the image of a city construction wind
12、ow, then developed automatic stop system inevitable. As required before the docking system bus GPS information (latitude and longitude information, etc.), longitude and latitude information generated by the distance between bus stops with the message that this is going to experience the tedious, use
13、 the micro-controller difficult to achieve, and when using chips, the proper solution of this problem. Using radians per second in the mathematics dealing with modulation makes the equation simpler. Of course, frequency is usually given in hertz, rather than in radians per second, when practical dev
14、ices are being discussed. It is easy to convert between the two systems per second, when practical devices are being discussed. It is easy to convert between the two systems by recalling from basic AC theory, =2f. In modulation, the parameters that can be changed are amplitude E, frequency , and pha
15、se . Combinations are also possible. For example, many schemes for transmitting digital information use both amplitude and phase modulation. Multiplexing is the term used in communications to refer to the combining of two or more information signals. When the available frequency range is divided amo
16、ng the signals, the process is known as frequency-division multiplexing (FDM). Radio and television broadcasting, in which the available spectrum is divided among many signals, are everyday examples of FDM. There are limitations to the number of signals that can be crowded into a given frequency ran
17、ge because each requires a certain bandwidth, For example, a television channel only occupies s given bandwidth of 6MHz in 68MHz bandwidth of VHF. Parallel DSP chip to enhance the performance of a traditional improved through the use of multiply-add units and the Harvard structure, it goes far beyon
18、d the computational capabilities of the traditional microprocessor. A reasonable inference is: chip operations by increasing the number of modules and the corresponding number of bus linking computational modules. The chip can be doubled to enhance the overall operational capacity. Of course, such a
19、n inference two preconditions must be met : First, the memory bus bandwidth as necessary to meet the increase in the number of enhanced data throughput； In addition, various functional units involved in the parallel scheduling algorithm is its complexity can be achieved. An alternative method for us
20、ing a single communication channel to send many signals is to use time-division multiplexing (TDM). Instead of dividing the available bandwidth of the channel among many signals, the entire bandwidth is used for each signal, but only for a small part of the time. A nonelectronic example is the divis
21、ion of the total available time on a television channel among the various programs transmitted. Each program uses the whole bandwidth of the channel, but only for part of the time. It is certainly possible to combine FDM and TDM, For example, the available bandwidth of a communication satellite is d
22、ivided among a number of transmitter-receiver combinations called transponders. This is an example of FDM. A single transponder can be used to carry a large number of digital signals using TDM. This course presents a top-down approach to communications system design. The course will cover communicat
23、ion theory, algorithms and implementation architectures for essential blocks in modern physical-layer communication systems (coders and decoders, filters, multi-tone modulation, synchronization sub-systems). The course is hands-on, with a project component serving as a vehicle for study of different
24、 communication techniques, architectures and implementations. This year, the project is focused on WLAN transceivers. At the end of the course, students will have gone through the complete WLAN System-On-a-Chip design process, from communication theory, through algorithm and architecture all the way to the synthesized standard-cell RTL chip representation.
