2. Course Information
• Lecture Timings
- Monday @ 11.30 a.m- 12.30 p.m
- Thursday @ 11.30a.m- 1.30 p.m
• Text Book
- Modern Analog and Digital Communication System by
B.P. Lathi, 4th Edition
3. Course Outline
Signal/Spectral Analysis
Power Spectral Density
Analog Modulation
AM-Suppressed Carrier, Single Side Band Modulation, Noise in AM
systems, Angle Modulation
Analog/ Digital Conversion
Sampling Theorem, Quantization (Types, Error), Pulse Modulation
Digital Transmission and Reception
Frequency and Phase Relationship, Amplitude Shift Keying (ASK), Frequency Shift
Keying (FSK),Phase Shift Keying, Transmission Media
Trends in Digital Communication Technology
Radio Systems, Satellite Communication Systems, Optical Communication Systems
5. Electrical Communication System
• Provide for electronic exchange of data
* Voice, data, video, music, email, web pages, etc.
• Information is converted to Electrical Signals for
transmission over copper, fiber optics or free space
Examples: Radio and TV broadcasting, Satellite systems, Cellular
Phones, Computer Networks, Optical Communication Systems
8. Communication System
Parts of communication system
•Source originates a message
•Transmitter modifies the message for efficient
transmission
•Channel is medium to convey electric signal
•Receiver processes the received signal to get
the actual message
9. Key Challenges
• Channel acts partly like a filter, which
attenuates
attenuates the signal and distorts
distorts the wave
form
- Loss in strength is attenuation
- Alteration of signal is distortion
10. Key Challenges
• Attenuation increases with the length of
the channel.
• Waveforms are distorted due to physical
phenomena e.g multipath effects,
frequency-selective channel or Doppler
shift
Factors causing Attenuation and Distortion
11. Types of Distortions
• Linear and Non linear
-Linear distortion slightly changes the
shape e.g square pulse changes to round
-Non-Linear distortion varies the signal
amplitude.
12. Noise
• Over the communication channel signals not only
experience distortion but also Noise
SO what is noise ?
It is unwanted form of energy which tends to
interfere with the desired signal
13. • The signal strength decreases along the
path while the noise level remains the
same.
Solution for attenuation problem ??
Amplification
15. Analog and Digital Messages
Digital Messages
- are combinations of finite symbols
Analog Messages
- characterized by data whose values vary
over a continuous range
16. • Document written in English is a digital message
digital message
constructed from the ASCII keyboard of 128
symbols
• Temperature or atmospheric pressure varies over
a continuous range of values.
Analog and Digital Messages
17. Current Trends
• Digital technology is replacing the old analog technology
-- Cell phones (first generation analog to digital
offspring)
-- VHS cassette system to DVDs
18. Why digital is BETTER ?
•Digital messages are transmitted as a finite set of
electrical waveforms.
•Each character in the alphabet is represented by
one waveform.
19. Why digital is BETTER ?
Sending a message which consists of two symbols e.g F
and G. An electric pulse of amplitude +ve A/2 can
represent F and a pulse of –ve amplitude for G
20. • Message extraction in easier from digital
signals than from analog
• Finite symbols leads to noise and interference
immunity.
Why digital is BETTER ?
