lecture 7-8 dsb-sc am mod i - at

8/18/2019 Lecture 7-8 Dsb-sc Am Mod i - At

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Communication Systems-

Communication Systems

Instructor: Dr. Muhammad Arif

[email protected]

The University of Lahore –Islamaad !ampus

Lecture 7-8Date 14 March 2016

mailto:[email protected]:[email protected]


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"

Overview

Chapter 4.1-4.2, Basics of amplitude modulation Baseband vs Carrier Modulation

Why Modulation

Double Side Band Carrier Suppressed Modulation (BSD-SC)

Types o Modulators

– Multiplier Modulator

– !inear Modulator

– Switchin" Modulator

– #in" Modulator

$re%uency Convertor

Demodulation o DSB-SC Si"nals


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Baseband and Carrier

Communication Baseband&

− Describes si"nals and systems whose ran"e o re%uencies is measuredrom ' to a maimum bandwidth or hi"hest si"nal re%uency

− oice& Telephone '-*+,./0 CD '-11+',./

− ideo& 2nalo" T 3+,M./4 T channel is '-5M./+ Di"ital4 dependin"on the si/e4 movement4 rames per second4 6

− 7ample& wire4 coaial cable4 optical iber4 8CM phone

Carrier Communication&− Carrier& a waveorm (usually sinusoidal) that is modulated to

represent the inormation to be transmitted+ This carrier wave is usuallyo much hi"her re%uency than the modulatin" (baseband) si"nal+

− Modulation& is the process o varyin" a carrier signal in order to usethat si"nal to convey inormation+

http://en.wikipedia.org/wiki/Waveformhttp://en.wikipedia.org/wiki/Sinusoidalhttp://en.wikipedia.org/wiki/Modulationhttp://en.wikipedia.org/wiki/Transmission_(telecommunications)http://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Carrier_wavehttp://en.wikipedia.org/wiki/Informationhttp://en.wikipedia.org/wiki/Informationhttp://en.wikipedia.org/wiki/Carrier_wavehttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Transmission_(telecommunications)http://en.wikipedia.org/wiki/Modulationhttp://en.wikipedia.org/wiki/Sinusoidalhttp://en.wikipedia.org/wiki/Waveform


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Communication-

Modulation


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Modulation Modulation

− 2 process that causes a shit in the ran"e o re%uencies o a si"nal+ 9ain advanta"es

− 2ntenna si/e& hal o the antenna si/e+ Thousands o miles or baseband

− Better usa"e o limited bandwidth& less side lopes

− Trade bandwidth or S:#& CDM2

− #obust to inter-symbol-intererence (multipath delay)

− #obust to errors and distortions

Types−

2nalo"& 2M (DSB4 SSB4 SB)4 $M4 Delta modulation− Di"ital& 2S4 $S4 8S4 ;2M4 6

− 8ulse modulation& 8CM4 8DM4 6 $iber4 phone

2dvanced& CDM2 (*9)4 O$DM (W!2:4 WM2:)4 6+


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#

2M-DSB-SC

7ample 3+<

0

0

Upper sideband (USB)Lower sideband (LSB)

0

→t

→t

→t

)( t m

)t(

ϕ

↑

)( ω M

→ω

)( ω Φ

→ωcωcω−

)t(ϕ

)tcos( cω

)= t c$% ω cos(

cω

π

→ω

)( t m)cos( ct ω


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Communication Systems

lecture 7-8 dsb-sc am mod i - at

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