EL323 Analog & Digital Communication- Lab Department of Electrical Engineering Prepared by: Engr. M. Sajid Iqbal and Engr. Qurat-ul-Ain, FAST-NU Karachi 3 Student ID: ___________________Section:______ Lab Number 1 Introduction to Elements of a Communication System ___________________________________________________________________________ After this lab you will be able to: Understand basic concepts of communication system Identify elements of communication system Understand analog & digital signals Understand the process of modulation & demodulation ___________________________________________________________________________ Communicationisthebasicprocessofexchanginginformation.Themainbarriertosignal communication is distance. Human communication took a dramatic turn in the late nineteenth century, when electricity was discovered and its many applications were explored. Well known forms of electronic communications such as telephone radio and television have increased our ability to share information. Today they are major part of our lives and now it is hard to imagine what our lives would be like without the knowledge and information that arrive from around the world by electronic communications. Communication System Allelectroniccommunicationsystemshavethreebasiccomponents,atransmitter,a communicationchannelormediumandareceiver.Inmostsystems,ahumangeneratesa messagethatwecalltheinformationsignal.Thissignalisinputtedtothetransmitterwhich thentransmitsthemessageoverthecommunicationchannel.Themessageispickedbythe receiver and is relayed to another human. Along the way, noise is added to the message in the communication channel. Noise is the general term applied to any interference that degrades the transmitted information. A typical communication system is shown in figure 1.1 below. Figure 1.1: A simple communication system In telecommunication, a communications system is a collection of individual communications networks,transmission/receivingsystems,relaystationanddataterminalequipment(DTE) usuallycapableofinterconnectionandinteroperationtoformanintegratedsystem.The components of a communications system serve a common purpose, are technically compatible, use common procedures, respond to controls, and operate in union. EL323 Analog & Digital Communication- Lab Department of Electrical Engineering Prepared by: Engr. M. Sajid Iqbal and Engr. Qurat-ul-Ain, FAST-NU Karachi4 Figure 1.2: Illustration of a wireless communication system Elements of a Communication System A communication system consists of a transmitter, a medium and a receiver. Whereas noise is also added to the transmitted signal. These elements are briefly described below. Transmitter (TX) It is a collection of electronic components and circuits designed to convert the information into a signal suitable for transmission over a given communication medium. It may be as simple as a microphone or as complex as a microwave radio transmitter. Communication Channel Thecommunicationchannelisthemediumbywhichtheelectronicsignalissentfrom one placetoanother.Thechannelcanbewiredorwireless(radio).Wiredchannelcanusethe mediumofcopperwireswhichcarryinformationfromoneplacetoanotherintheformof electriccurrentoritcanbeopticalfiberthatcarriesmessageonalightwave.Ontheother hand, the channel may be wireless or radio which carries information as electromagnetic waves. Receiver (RX) Thereceiverisanothercollectionofelectroniccomponentsandcircuitsthatacceptthe transmittedmessagefromthechannelandconvertitbackintoasimplefromwhichis understandable by humans. Noise Noiseisrandom,undesirableelectricenergythatentersthecommunicationsystemviathe communicationmediumandinterfereswiththetransmittedmessage.Noisecomesfromthe atmosphere,outerspaceradiationsandelectricalinterferencecreatedbymanufactured equipment.Noisecannotcompletelyeliminated, howeveritcanbecontrolledorfilteredfor correct signal reception. Types of Signals The signals in a communication system are either analog or digital. Analog Signals An analog signal is a continuously varying voltage or current. A typical analog signal is a sine wave tone. Voice and video voltages are analog signals. EL323 Analog & Digital Communication- Lab Department of Electrical Engineering Prepared by: Engr. M. Sajid Iqbal and Engr. Qurat-ul-Ain, FAST-NU Karachi 5 Digital Signals A digitalsignalisa physicalsignalthatisarepresentationofasequenceof discretevalues. Data used in computers is also digitized where binary codes representing numbers, letters, and special symbols are transmitted by wire or radio. Intodaysworldanalogdataisalsoconvertedintodigitalformandthentransmitted.One advantage of digital information is that it tends to be far more resistant to be transmitted and interpreted errors than information symbolized in an analog medium. Modulation & Demodulation Modulationistheprocessofmodifyingthecharacteristicofonesignalinaccordancewith some characteristic of another signal. In most cases, the information signal, be it voice, video, binary data or some other information is used to modify an attribute of high frequency signal known as carrier.The information signal is called the modulating signal, and the high frequency signal which is beingmodulatediscalledthecarrierandthesignalresultasamodulationprocessincalled modulated signal. The carrier is generally a sine wave while modulating signal can be of any shape, permitting both analog and digital signals to be transmitted. If modulating or information signal is analog then this is called analog modulation and if it is digital then this is called digital modulation. In most cases the carrier frequency is considerably higher than the highest information frequency to be transmitted.Theretrievalofinformationfromthemodulatedwaveatthereceivingendisknownas Demodulation process. Data and Information Datareferstothelowestabstractorarawinputwhichwhenprocessedorarrangedmakes meaningful output. Information is usually the processed outcome of data. EL323 Analog & Digital Communication- Lab Department of Electrical Engineering Prepared by: Engr. M. Sajid Iqbal and Engr. Qurat-ul-Ain, FAST-NU Karachi 6 Lab Exercise 1.What is the purpose of a transducer in a communication system? Explain with an example. ______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ 2.What are the advantages of modulation? _________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ _________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ __________________________________________________________________________________________________________________________________________ 3.Differentiate between data and information with examples. _________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ _______________________________________________________________________________________________________________________________________________________________________________________________________________