INTRODUCTION TO PRINCIPLES OF COMMUNICATION ENGINEERING PART 1 LECTURE 1 INTRODUCTION TO PRINCIPLES OF COMMUNICATION ENGINEERING PART 1

of COMMUNICATION SYSTEM? WHAT DO YOU UNDERSTAND of COMMUNICATION SYSTEM?

DEFINITIONS OF COMMUNICATIONS Humans exchanging information Machines exchanging information Conveying thoughts, feelings, ideas, and facts Sending and receiving information by electronic means

BARRIERS TO COMMUNICATIONS Language: human, computer, or electronic Distance: space between sending and receiving parties

COMMON FORMS OF COMMUNICATIONS Human voice: face-to-face conversations, public speakers, actors in plays, etc. Audio: CDs, tape, records, radio Body language: non-verbal Print: newspapers, magazines, books, etc. Film: still and movie Video: movies, graphics and animation Music: personal, concerts

FORMS OF ELECTRONIC COMMUNICATIONS Radio and TV broadcasting Telephone, wired and wireless Fax Pagers Computer networks: modem, e-mail, Internet and World Wide Web, wireless Satellites, radar, radio telescopes

Communication systems

Basic components:  Transmitter  Channel or medium  Receiver  Noise degrades or interferes with transmitted information.

Communication Systems Transmitter The transmitter is a collection of electronic components and circuits that converts the electrical signal into a signal suitable for transmission over a given medium. Transmitters are made up of oscillators, amplifiers, tuned circuits and filters, modulators, frequency mixers, frequency synthesizers, and other circuits.

Communication Systems Communication Channel The communication channel is the medium by which the electronic signal is sent from one place to another. Types of media include Electrical conductors Optical media Free space System-specific media (e.g., water is the medium for sonar).

Communication Systems Receivers A receiver is a collection of electronic components and circuits that accepts the transmitted message from the channel and converts it back into a form understandable by humans. Receivers contain amplifiers, oscillators, mixers, tuned circuits and filters, and a demodulator or detector that recovers the original intelligence signal from the modulated carrier

Communication Systems Transceivers A transceiver is an electronic unit that incorporates circuits that both send and receive signals. Examples are: Telephones Fax machines Handheld CB radios Cell phones Computer modems

Communication Systems Noise Noise is random, undesirable electronic energy that enters the communication system via the communicating medium and interferes with the transmitted message.

TYPES OF COMMUNICATIONS TX Channel RX Simplex: One-way Duplex: Two-way Half duplex: Alternate TX/RX Full duplex: Simultaneous TX/RX TX RX Channel(s) TX RX

TYPES OF COMMUNICATIONS SIGNALS Analog - smooth and continuous voltage variation. Digital - binary or two voltage levels. Time

COMMUNICATIONS SIGNAL VARIATIONS Baseband - The original information signal such as audio, video, or computer data. Can be analog or digital. Broadband - The baseband signal modulates or modifies a carrier signal, which is usually a sine wave at a frequency much higher than the baseband signal.

Basic analog communications system Baseband signal (electrical signal) EM waves (modulated signal) Transmitter Input transducer Transmission Channel Modulator EM waves (modulated signal) Carrier Baseband signal (electrical signal) Receiver Output transducer Demodulator

MODULATION An electronic technique in which a baseband information signal modifies a carrier signal (usually a sine wave) for the purpose of frequency translation and carrying the information signal via radio. The common types of modulation are amplitude, frequency and phase.

Why modulation is needed? To generate a modulated signal suited and compatible to the characteristics of the transmission channel. For ease radiation and reduction of antenna size Reduction of noise and interference Channel assignment Increase transmission speed

Modulation at the transmitter

AMPLITUDE MODULATION higher than the baseband frequency The modulating (baseband) signal is a sinusoid in this example. High-frequency carrier, normally much higher than the baseband frequency

FREQUENCY MODULATION The baseband signal controls the carrier’s frequency and the carrier’s amplitude remains constant.

FM Resting fc Increasing fc Decreasing fc Increasing fc Resting fc Modulating signal Carrier

MULTIPLEXING Multiplexing (MUX or MPX) - the process of simultaneously transmitting two or more baseband information signals over a single communications channel. Demultiplexing (DEMUX or DMPX) - the process of recovering the individual baseband signals from the multiplexed signal.

MULTIPLEXING AND DEMULTIPLEXING Single communications channel (radio or cable) MUX DEMUX Recovered baseband information signals Original baseband information signals

Modulation and Multiplexing

ELECTRONIC COMMUNICATIONS APPLICATIONS Radio broadcasting (AM & FM) Television broadcasting (analog & DTV) Cable TV Wireless remote control Paging Navigation and direction finding Telemetry

ELECTRONIC COMMUNICATIONS APPLICATIONS (Continued) Radio astronomy Surveillance RF identification (ID) Music services Telephones (wired, cordless, cellular) Facsimile Two-way radio

ELECTRONIC COMMUNICATIONS APPLICATIONS (Continued) Radar Sonar Amateur radio Citizens and family radio Data communications Networks Internet and World Wide Web

FREQUENCY AND WAVELENGTH Cycle - One complete occurrence of a repeating wave (periodic signal) such as one positive and one negative alternation of a sine wave. Frequency - the number of cycles of a signal that occur in one second. Period - the time distance between two similar points on a periodic wave. Wavelength - the distance traveled by an electromagnetic (radio) wave during one period.

PERIOD AND FREQUENCY COMPARED T = One period time One cycle Frequency = f = 1/T

Frequency and wavelength compared + T time f = 1/T  distance

CALCULATING WAVELENGTH AND FREQUENCY  = wavelength in meters f = frequency in MHz

THE ELECTROMAGNETIC SPECTRUM FROM 30 HZ TO 300 GHZ Wavelength ( = 300/f) 107 m 106 m 105 m 104 m 103 m 102 m 10-1 m 10-2 m 10-3 m 10-4 m 10 m 1 m Millimeter waves ELF VF VLF LF MF HF VHF UHF SHF EHF 30 Hz 3 kHz 300 Hz 30 kHz 3 MHz 3 GHz 300 kHz 30 MHz 30 GHz 300 MHz 300 GHz (f = 300/) Frequency

LOW AND MEDIUM FREQUENCIES Extremely Low Frequencies - 30 to 300 Hz Voice Frequencies - 300 to 3000 Hz Very Low Frequencies - 3 kHz to 30 kHz Low Frequencies - 30 kHz to 300 kHz Medium Frequencies - 300 kHz to 3 MHz

HIGH FREQUENCIES High Frequencies - 3 MHz to 30 MHz Very High Frequencies - 30 MHz to 300 MHz Ultra High Frequencies - 300 MHz to 3 GHz (1 GHz and above = microwaves) Super High Frequencies - 3 GHz to 30 GHz Extremely High Frequencies - 30 GHz to 300 GHz

THE ELECTROMAGNETIC SPECTRUM ABOVE 300 GHZ Wavelength 0.8 x 10-6 m 0.4 x 10-6 m 10-3 m 10-4 m 10-5 m Millimeter waves Ultraviolet Infrared X-rays Visible Gamma rays Cosmic rays 300 GHz

OPTICAL FREQUENCIES Infrared - 0.7 to 10 micron Visible light - 0.4 to 0.8 micron Ultraviolet - Shorter than 0.4 micron Note: A micron is one millionth of a meter. Light waves are measured and expressed in wavelength rather than frequency.

Noise, interference and distortion Noise:unwanted signals that coincide with the desired signals. Noise is random, undesirable electric energy. Two type of noise:internal and external noise. Internal noise: Caused by internal devices/components in the circuits. External noise:noise that is generated outside the circuit. Eg: atmospheric noise,solar noise, cosmic noise, man made noise. Interference-one type of external noise Distortion: signal being distorted

Limitations in communication system Physical constraint -Delay, attenuation, bandwidth limitation, etc Technological constraint hardware. Expertise - economy, law

Frequency Spectrum &Bandwidth The frequency spectrum of a waveform consists of all frequencies contained in the waveform and their amplitudes plotted in the frequency domain. The bandwidth of a frequency spectrum is the range of of frequencies contained in the spectrum.It is calculated by subtracting the lowest frequency from the highest.

Frequency Spectrum &Bandwidth (cont’d) Bandwidth of the information signal equals to the difference between the highest and lowest frequency contained in the signal. Similarly, bandwidth of communication channel is the difference between the highest and lowest frequency that the channel allow to pass through it