Analog Communication, Summaries of Communication

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EEE 431

Analog Communication

Lecture

Course Overview

Lecture Overview

 The objectives of today’s lecture are

 Explain the course mechanics  Provide an overview of the course  Describe the major components of theDescribe the major components of the course  List the prerequisite knowledge required

 Reading

 Chapter 1  Chapter 2

Required Course Materials

 Textbook:  B.P. Lathi, Modern Digital and Analog Communication Systems, 4th Ed., Oxford University Press, 2010.  References:  Simon Haykin, Communication Systems, 4th ed., John Wiley & Sons, 2001.John Wiley & Sons, 2001.  Mischa Schwartz, Information Transmission, Modulation and Noise, 4th Ed., McGraw-Hill,1990.  A.B. Carlson, P.B. Crilly, J. C. Rutledge, Communication Systems, 4th Ed., McGraw-Hill, 2002.  H.P. Hsu, Analog and Digital Communcations, Shaum’s Outline Series, McGraw-Hill.  Software:  Matlab for Windows

Course Components

 The course has four main components:  Lectures – These are meant to introduce the key concepts in the course and provide you with fundamental understanding. This is the primary source of information in the class. I will provide you with lecture notes on the website typically the weekend before class (no guarantees though). As part of the lectures we will have in-class drill problems which allow you to interact with the material and keep you involved. Attending the lectures is absolutely crucial to successfully completing thislectures is absolutely crucial to successfully completing this course!  Book –This is meant to supplement the lectures and provide more detail that cannot be covered in lecture times.  Exams – These are meant to show me how well you have grasped the material.

Course Objectives

 After successfully completing this course the student should be able to  Compute the Fourier transform and the energy/power spectral density of communications signals.  Calculate the bandwidth and signal-to-noise ratio of a signal at the output of a linear time-invariantof a signal at the output of a linear time-invariant system given the signal and the power spectral density of the noise at the input of the system.  Explain the operation of amplitude and angle modulation systems in both the time and frequency domains including plotting the magnitude spectra and computing the power and bandwidth requirements of each type of signal.

Course Objectives (cont.)

 After successfully completing this course the student should be able to  Design a basic analog communication system including: (1) the selection of a analog modulation format, (2) the block-diagram design of a transmitter for the system, (3) the block-of a transmitter for the system, (3) the block- diagram design of a superheterodyne receiver for the system, (4) the design of a time or frequency division multiplexing scheme, as appropriate to meet performance requirements.  Evaluate a given analog communication system in terms of the complexity of the required transmitters and receivers and the power and bandwidth requirements of the system.

Overview of the Course

 The course can be broken down into

two basic segments:  Section I – Signals and System Theory applied to communicationsapplied to communications  Section II – Analog Communication

What is Communication?

 Definition: Communication is the transfer of information at one time or location to another time or location.

 Generic Communication System:Generic Communication System:

Channel

Transmitter Receiver

Received signal

Transmitted signal Communication System

Estimate of message signal

User of information

Source of information (^) Message signal

Primary Communication Resources

 Transmitted power

 The average power of the transmitted signal

 Channel bandwidth

 The band of frequencies allocated for the transmission of the message signal  band-limited channels  Telephone systems: 300-3100 Hz  Power-limited channels  Satellite channel

A Communication System

 Source of Information

 Information may take many forms: computer data, image, voice, music, video.  Information can be either analog or digital.  Analog information can also be ‘digitized’.  Information is defined as the amount ofInformation is defined as the amount of “surprise” at the rx.

 Transmitter

 Processes information and puts it into a form suitable for transmission  This typically means transforming into an electromagnetic signal  Can be either ‘baseband’ or ‘bandpass’

A Communication System (Contd.)

 Modulation

 Modification of the message signal by the transmitter in a form suitable for transmission. Demodulation

Modulated signal

Message signal

Carrier

 Demodulation

 Recreation of the message signal from received signal (a degraded version of the transmitted signal)

Modulation

 Continuous-wave (CW) modulation  A sinusoidal wave is used as the carrier  Amplitude modulation (AM)  Frequency modulation (FM)  Phase modulation (PM)

 Pulse modulationPulse modulation  Carrier consists of periodic sequence of rectangular pulses  Analog pulse modulation  Pulse-amplitude modulation (PAM)  Pulse-duration modulation (PDM)  Pulse-position modulatiob (PPM)  Digital pulse modulation  Pulse-code modulation (PCM)

Examples of Communication Systems

 Broadcast Radio  Music and voice are transmitted from a broadcast station to large number of receivers (i.e., radios) over the air  Broadcast Television  Images are transmitted from a broadcast station to a large number of receivers (i.e., TVs) over the air  Telephone system  Voice (digital data also possible) transmitted from one point toVoice (digital data also possible) transmitted from one point to another point (i.e., one phone to another) through wires (both copper and optical fiber)  Cellular telephone  Voice (digital data also possible) transmitted from one point to another point through both wires and over the air  Internet (computer networks)  Digital data transmitted from one point to another point through wires  Satellite communication systems  Digital data or voice transmitted from one point to another point using satellite as an intermediate transmitter/receiver

What Makes a Good Communication System

 Good Received Signal Fidelity  Analog System: high Signal-to-Noise Ratio (SNR)  Digital System: low Bit Error Rate (BER)

 Low Transmit Signal Power

 A large amount of information isA large amount of information is transmitted

 Signal occupies a small bandwidth

 System has a low cost (complexity?)  Complex digital operations have steadily grown cheaper

 Communications engineers must trade off all of these