Embed Size (px)
DESCRIPTION
Basics of a Communication System
Citation preview
COMMUNICATION SYSTEMS
Elements of Communication Sytems!
The Source!
The Channels!
Types of Modulation!
Signal Bandwidth
OUTLINE
ELEMENTS OF
COMMUNICATION SYSTEM
SOURCE TRANSMITTER RECEIVER DESTINATION
CHANNEL
ELEMENTS OF
COMMUNICATION SYSTEM
SOURCE* TRANSMITTER RECEIVER DESTINATION
CHANNEL
• need to be in FORM to pass through CHANNEL
!• to employ
*SOURCE
TRANSMITTER and RECEIVER
ELEMENTS OF
COMMUNICATION SYSTEM
`
SIGNAL MODULATED CARRIERS
about 300 Hz - 3 kHz
High-Fidelity Music
about 20 Hz - 20 kHzFrequency (Hz)
!
"
A N A L O G
about 4.2 Mhz
⇛SOURCEVoice
Video (TV)
ELEMENTS OF
COMMUNICATION SYSTEM
SOURCE
SIGNAL FREQUENCIES
Voice
Alphanumeric
ANY Bandwidth !!!DEPENDENT: !□ Transmission (bps) □ Method to convert binary 1’s & 0’s to electrical signal
Frequency (Hz)!
"
D I G I T A L
Video
⇛
ELEMENTS OF
COMMUNICATION SYSTEM
CHANNEL (a path for transmission of signal)
TYPES
Modulated Carriers !
• information signal • modulating signal • baseband
BASEBAND Frequency spectrum of information signal
"⇛
Carrier Signals
!
Analog
Digital
Carrier Frequency HIGHER THAN Information Signal
CONDUCTOR PAIRS (DIRECT)
FIBER OPTICS
FREE SPACE
RADIO LINK !
• Not OK for DIRECT LINK • Needs HIGHER ANTENNA • INTERFERENCE • Needs CARRIER
• Process by which some characteristics of the carrier wave is varied in accordance with an information-bearing signal.$
• Done at Transmitter (TX)!• Demodulation (Detection) done at Receiver (Rx)$!
MODULATION
! Carrier is Sine Wave!
e(t) = Ec sin (wct + θ)!!
where e(t) = instantaneous voltage as a function of time$$ Ec = peak voltage (Amplitude)$$ wc = frequency in radians per second$$ t = time in seconds$$ θ = phase angle in radians$
SIGNAL BANDWIDTH
!I = ktB!
! where I = amount of information to be sent!! k = a constant dependent on modulation type (i.e. AM, FM, PCM etc.)!! t = time available!! B = channel bandwidth$
Hartley’s Law
FREQUENCY DIVISION MULTIPLEXING (FDM)
! Combining of two or more information signals.$
Multiplexing
! Process of dividing available frequency range among signals.$
Frequency Division Multiplexing (FDM)
TYPES OF MODULATION
SOURCE* TRANSMITTER RECEIVER DESTINATION
CHANNEL
• need to be in FORM to pass through CHANNEL
!• to employ
*SOURCE
TRANSMITTER and RECEIVER
