Let us start a 3 semester course on communication

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Let us start a 3 semester course on
communication

• Comm. Engg. I (3rd Semester)
• Comm. Engg. II (4th Semester)
• Mobile Comm. (7th Semester)

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• Neetesh Purohit
• Lecturer, IIIT,
• Allahabad, UP, India
• http//profile.iiita.ac.in/np/
• (Other details, course material, assignments,
  midsem, endsem marks, notices etc are available.)

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General Information

• The Book for 3rd and 4th Sem Communication
  Systems, IV Edition, A. B. Carlson and others,
  McGraw Hills.
• Proportionate marks for attendance (10).
• Quiz marks (1010)
• Unsolved problems at the end of all chapters is
  an assignment. You should try to solve 5 problems
  within 2 days after completion of chapter in your
  assignment copy. (15)
• The problem numbers will be (your roll number
  x) mod N x0,4,8,12,16 And N number of problems

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What is communication?

• Some information is available at a place and the
  way of transferring this information to a distant
  place is called communication.
• Information may be an idea in someones mind or
  it may be a news that something has been happened
  or will happen etc.

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Various types of Comm. systems

• Postal system
• Telephone, mobile
• Fax, etc
• What is the common requirement of these systems
  to function properly?

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• The available information must be transformed in
  a form which is compatible with characteristics
  of the communication system
• What does it mean?

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Electrical Communication system

• Information Information

I/P Transducer
O/P Transducer
Electrical signal
Receiver
Transmitter
channel
Twisted Copper wire coaxial cable optical
fiber space
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Tx and Rx sections

• Each channel has some characteristics features
  e.g. copper cables carry voltages/currents, EM
  wave travels thru space etc. besides some
  fundamental limitations.
• The job of transmitter is to provide
  compatibility at this stage.
• The job of receiver is to perform inverse
  operation of Tx.

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Fundamental limitations

• Noise
• - thermal agitation of electrons produces
  thermal noise, as explained in kinetic theory of
  gases.
• - S/N ration must be maintained

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• Bandwidth
• - stored energy in inductances and capacitances
  can not be changed instantaneously.
• - Copper channels have distributed capacitances
  and inductances
• -Telephone cables act as low pass filters and
  attenuate high frequency components. It results
  in distortion.

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Designing of an Analog comm. system

• Estimation of BW of intended analog signals
• Select a channel such that
• BW of system gt BW of signal
• Design the Tx and Rx.
• Measure the performance in terms of fidelity

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Modulation

• Systematic alteration of a parameter of carrier
  wave (amplitude, phase and frequency) in
  accordance with instantaneous value of the
  message signal.
• Alteration in frequency domain properties of
  modulated signal

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Advantages of modulation

• Frequency Assignment and multiplexing
• Practicability of antenna (minimum dimension of
  an antenna should be at least ?/10)
• Reduce noise and interference

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• Unit I
• Line spectra and Fourier series, Gibbs
  phenomenon, Parsval theorem, Fourier Transform
  and its properties, Rayleigh theorem, Convolution
  operation, Impulses and Transforms in the limits
• Unit II
• Signal distortion in transmission, pulse
  response and rise time, Quadrature Filters and
  Hilbert Transform, Correlation functions,
  Schwartz inequality, Wienner Kinchie theorem, t
  domain analysis of linear systems.
• Unit III
• Advantages of modulation, DSB-SC, SSB and AM
  modulation techniques, Modulators and
  Transmitters for AM

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• Unit IV
• Frequency modulation technique, Deemphasis,
  capture effect in FM, Signal transmission and
  detection, Commercial FM Transmitter and super
  heterodyne receiver.
• Unit V
• Analog to digital conversion Sampling theorem,
  Natural and flat top sampling, uniform and
  non-uniform quantization, Reconstruction of
  signal, PCM, delta and adaptive delta modulation,
  ADPCM.
• Unit VI
• Noise Thermal noise, white noise, available
  power, noise equivalent bandwidth, noise
  temperature, circuit and system noise, noise
  figure, the concept of signal space, Gram Schmidt
  procedure.