1 ENE 429 Antenna and Transmission lines Theory Lecture 2 Uniform plane waves.
Transmission Lines Lecture 01
Transcript of Transmission Lines Lecture 01
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ECEn513 Lecture # 1
Transmission Lines
Ramel E. Recentes
La Salle University
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Introduction
Transmission Media can be generally
categorized as either
guided
unguided
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Guided media are those with some form ofconductor that forms a conduit between Tx and Rx.Unguided media include free space, air or even
water.
Guided Media can be further be categorised as
transmission lines or metallic cables
optical fibers
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A transmission lineis a metallic conductor
system used to transfer electrical energy from
one point to another. It is made up of 2 or more
electrical conductors separated by insulator.
When propagating signals at DC or low
frequencies the behaviour of TL is predictable.
However, at high frequencies it becomescomplex.
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Wave Basics
Types of waves
1. longitudinal waves the displacement
(amplitude) is in the direction of propagation.Examples: water waves, sound wave
2. transverse waves the direction of displacementis perpendicular to the direction of propagation.
Ex. TEM
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TEM (Transverse Electromagnetic Waves) are
waves consisting of electric and magnetic
components. Transmission of power along a TL
is in the form of TEM.
The TEM propagates primarily in the dielectric
part.
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In conductors, current and voltage are always
accompanied by an electric ( E) field and a
magnetic (H) field.
Electromagnetic waves that travel from sourceto load are called incident waves. Waves that
travel back are referred to as reflected waves.
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The Transverse Electromagnetic Wave
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Wave Velocity, Frequency and
Wavelength
Wave Velocity speed of TEM waves along a certainmedium.
Light Speed = 186.283 miles/ sec or 299,793,000 m/s
TEM waves travel slightly slower depending on thedielectric used. But generally it is approximated at
3 X 108
Frequency The rates at which the wave repeats
Wavelength The distance of one cycle.
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A wave
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Examples:
1. Calculate the wavelength of a wave with
frequency of 145Mhz.
2. Determine the frequency for electromagnetic
waves with wavelengths 1cm and 10m.
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Types of Transmission Lines
balanced
unbalanced
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Balanced Transmission Line
With two wire balanced transmission lines , both
conductors carry current; however , one conductorcarries the signal and the other is the return path.
Unbalanced Transmission Line
With unbalanced transmission line, one wire is atground potential, whereas the other wire is atsignal potential.
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Figure A . Differential or Balanced Transmission Line
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Figure A : Single ended or unbalanced transmission system
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Balun- A circuit device used to connect a
balanced transmission line to unbalanced
transmission line (balanced to unbalanced)
Examples of balun
transformer balun
bazooka balun or choke /sleeve
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Transformer Balun
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Metallic Transmission Lines
Standard metallic transmission lines can either
be :
Parallel Conductor TL
Coaxial (Concentric) TL
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Parallel Conductor TL are comprised of two or
more metallic conductors (usually copper)
separated by a nonconductive insulating
material called dielectric. Dielectrics canbe air, rubber, polyethylene, paper, mica,
glass, and Teflon.
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Common types
open wire TL
twin lead
twisted pair ( includes UTP or unshielded
twisted pair and STP or shielded twisted pair)
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Open Wire Transmission Line
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Twin Lead Transmission Line
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Twisted Pair Transmission Line
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EIA/TIA 568 UTP and STP levels and
Categories
UTP Unshielded twisted pair (100 ohms)
STP Shielded twisted pair (150 ohms)
Size of twisted pair varies from 16AWG to 26AWG.
Standards cable varies from 22AWG to 24AWG.
Minimum number of twists is 2 per foot.
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EIA/TIA 568 UTP and STP levels and
Categories
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Cat 5 cable
Most commonly used in todays local areanetworks
Comprised of 4 pairs of wires 2 are unused.
Pair 1 : blue/white stripe and blue
Pair 2 : orange/white stripe and orange
Pair 3 : green/white stripe and green
Pair 4 : brown/white stripe and brownCan be Cat5 flex or Cat5 solid
An improved version is CAT5E (enhanced)
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Proposed new categories
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Cat 5 cable
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Plenum Cable
a cable that is laid in the plenum spaces of
buildings. The plenum is the space that can
facilitate air circulation for heating and air
conditioning systems, by providing pathwaysfor either heated/conditioned or return
airflows.
A plenum type cable meets thermalrequirements to be used in the plenum.
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Coaxial Cables
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Coaxial Cables
Basic Types
(a)rigid air field
(b)solid flexible
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RG series cables (RG = Recommended
Guide)
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Coaxial cable Connectors
BNC Connector
BNC Barrel
BNC T
Type N
Type N barrel
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BNC Connector
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BNC Barrel
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BNCT
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Type N connector
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Type N Barrel
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Assignment
Choose a specific cable number ( parallel or
coaxial) and do the following:
(a) Secure a sample (at least 1 meter long)
(b) Research the specification
(c) Identify the common uses(d) Bring your cable and prepare a short
presentation for b and c.
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End of Part 1
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Now the engineering part.