COURSE TOPICS

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COURSE TOPICS

• Elements of a Communication System
• Fourier
• Noise
• Transmission Lines
• Antennas
• Waveguides
• Microstrip
• S parameters
• Radar

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ELEMENTS OF A COMMUNICATION SYSTEM

• Source
• Transmitter
• Channel
• Receiver
• Destination

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SOURCE EXAMPLES

• Analog/digital audio and video
• Data communications

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TRANSMITTER

• Radio and T.V. Stations
• Cell Phones
• Dispatch Sysytems
• INFORMATION SIGNAL IS COMBINED WITH A MODULATING
  SIGNAL

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CHANNEL

• Pair of Conductors
• Fibre Optic Cable
• Free Space

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RECEIVER

• Demodulator
• Detector

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DESTINATION

• Image Display
• Speaker
• Computer

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COMMUNICATION CONSIDERATIONS

• Types of Modulation A.M., F.M etc.
• equation for
• sine wave
• carrier
• Bandwidth I ktB k is modulation type constant
  and B channel bandwidth
• FDM
• TDM
• Band Allocations

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TYPES OF MODULATION

• ANALOG
• AM, FM and PM
• DIGITAL
• FSK, PSK, QPSK and QAM

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SIGNAL BANDWIDTH

• How much bandwidth is required by an unmodulated
  sine wave carrier?
• Shannon-Hartley Law
• What is the Baseband signal?
• - the band of frequencies occupied by the
  information signal.

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FREQUENCY DIVISION MULTIPLEXING

• Defininition
• When available spectrum is divided among many
  signals.
• What are some examples?
• 1. Television broadcast spectrum.
• 2. Radio broadcasting.

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FREQUENCY BANDS

• R.F. spectrum (refer to table)
• Frequency vs. wavelength

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v velocity of wave in m/s f frequency of
wave in Hz wavelength in meters
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RADIO WAVES IN FREE SPACE

• Velocity of radio wave is same as for light
  waves.
• c speed of light m/s

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WAVELENGTH EXAMPLE

• Determine and compare the wavelengths of a signal
  at 4 Ghz and 1 Mhz.

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Transmission and Distortions

• Distortions
• Harmonic
• Intermodulation
• Nonlinear frequency rresponse
• Nonlinear phase response
• Noise
• Interference

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FOURIER SERIES

• Any well-behaved periodic waveform can be
  represented as a series of sine and or cosine
  waves at multiples of its fundamental frequency
  plus a d.c. offset where it exists.
• f(t) Ao/2 A1 cos wt B1 sin wt A2 cos 2wt
  B2 sin 2wt A3 cos 3wt B3 sin 3wt where
• f(t) any well behaved function of time
• An and Bn real number coefficients
• w radian frequency of the fundamental
• f 1/T w 6.28f

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FOURIER POLYNOMIAL OF DEGREE n

• k 1,2n and repeats every 2

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Time Domain
V

1
0
1
-1
t (ms)
Frequency Domain
(V) Vp
1.0
f (kHz)
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Identify the location of harmonic content, in the
frequency domain, for the square wave below.
Hint Is this an odd function or even function
square wave?
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v (V)
1
t (ms)
1
Vp (V)
1 2 3
4 5 6
7
f (kHz)
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V
5 4 3 2 1 0
1 2
3 t (ms)
Find the Fourier series for the signal above.
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V
5 4.5 4 3.5 3 2.5
2 1.5 1 0.5 0

1 2
3 4
5
f (kHz)
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Filters and Signals

• Why is the output signal distorted?

Some significant frequency components have not
passed through the filter. Assume an input
frequency of 1 Mhz. Where does the cutoff
frequency of the filter fall?
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NOISE AND COMMUNICATIONS

• Where does noise originate in a communication
  system?
• 1. Channel
• 2. Equipment
• DEFINE
• -undesired random variations that interfere
  with the desired signal and inhibit
  communication.
• REMEDIES?
• 1. Reduce Bandwidth
• 2. Increase transmitter power
• 3. Low Noise Amplifiers

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TYPES OF NOISE

• TWO CATEGORIES
• 1. External Noise
• 2. Internal Noise

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EXTERNAL NOISE

• 1. Equipment Noise
• - automobile engines
• - electric motors
• - computers
• - light dimmers
• 2. ATMOSPHERIC NOISE (STATIC)
• - Lightning
• - Noise Blanking
• 3. SPACE NOISE
• - Radiation from the Sun (solar noise)
• - Stellar or Sky Noise (stars)