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1、Introduction to Communication SystemIt 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 a channel. F
2、igure 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.SourceTransmitterReceiverDestinationFigure 1 simple communication s
3、ystemThe source or information 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
4、, while analog high-fidelity 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 electri
5、cal signals.A communication 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
6、 radio link through 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 signa
7、l is also known as the 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 re
8、al world signals digitally 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 a
9、nd healthcare. For 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 d
10、ata storage and error 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 conges
11、tion, 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 window, then developed au
12、tomatic 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 the micro-controller
13、 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 devices are being discus
14、sed. 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 phase . Combinations are
15、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 among the signals, the pro
16、cess 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 range 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 enhan
