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LECTURE 1

LECTURE 1. INTRODUCTION TO PRINCIPLES OF COMMUNICATION ENGINEERING PART 1. WHAT DO YOU UNDERSTAND . of COMMUNICATION SYSTEM?. DEFINITIONS OF COMMUNICATIONS. Humans exchanging information Machines exchanging information Conveying thoughts, feelings, ideas, and facts

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LECTURE 1

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

  2. WHAT DO YOU UNDERSTAND of COMMUNICATION SYSTEM?

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

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

  5. 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

  6. 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

  7. Communication systems

  8. Basic components:  Transmitter  Channel or medium  Receiver  Noisedegrades or interferes with transmitted information.

  9. 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.

  10. 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).

  11. Communication Systems Receivers • A receiveris 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

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

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

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

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

  16. 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.

  17. 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

  18. 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.

  19. 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

  20. Modulation at the transmitter

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

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

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

  24. 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.

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

  26. Modulation and Multiplexing

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

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

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

  30. FREQUENCYANDWAVELENGTH • 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.

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

  32. Frequency and wavelength compared T  + 0 time f = 1/T distance

  33. CALCULATING WAVELENGTH AND FREQUENCY  = 300/f f = 300/  = wavelength in meters f = frequency in MHz

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

  35. 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

  36. 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

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

  38. 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.

  39. 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

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

  41. 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.

  42. 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

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