Líneas de Transmisión

1. 7e Applied EM by Ulaby and Ravaioli
2장 전송선 본문1

2. 2. TRANSMISSION LINES
Applied EM by Ulaby, Michielssen and Ravaioli
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3. Chapter 2 Overview
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4. Transmission Lines
A transmission line connects a generator to a load
Transmission lines include:
• Two parallel wires
• Coaxial cable
• Microstrip line
• Optical fiber
• Waveguide
• etc.
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5. Transmission Line Effects
Is the pair of wires connecting the voltage
source to the RC load a transmission line?
Yes.
The wires were ignored in circuits courses.
Can we always ignore them? Not always.
Delayed by l/c
At t = 0, and for f = 1 kHz , if:
(1) l = 5 cm:
(2) But if l = 20 km:
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6. Dispersion
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7. Types of Transmission Modes
TEM (Transverse
Electromagnetic):
Electric and
magnetic fields
are orthogonal to
one another, and
both are
orthogonal to
direction of
propagation
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8. Example of TEM Mode
Electric Field E is radial
Magnetic Field H is azimuthal
Propagation is into the page
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9. Transmission Line Model
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10. Expressions
will be
derived in
later
chapters
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11. Transmission-Line Equations
ac signals: use phasors
Telegrapher’s
equations
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12. Derivation of Wave Equations
Combining the two equations leads to:
Second-order differential equation
complex
propagation constant
attenuation
constant
Phase constant
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13. Solution of Wave Equations (cont.)
Proposed form of solution:
Using:
It follows
that:
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14. Solution of Wave Equations (cont.)
In general:
wave along +z because coefficients of t and z
have opposite signs
wave along –z because coefficients of t and z have
the same sign
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15. Example 2-1: Air Line
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18. Lossless Microstrip Line
Phase velocity in dielectric:
Phase velocity for microstrip:
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19. Lossless Microstrip Line
Quasi-TEM
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20. Microstrip (cont.)
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21. Microstrip (cont.)
Inverse process:
Given Z0, find s
The solution formulas are based on
two numerical fits, defined in terms
of the value of Z0 relative to that
of the effective permittivity.
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24. Lossless Transmission Line
If
Then:
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26. Voltage Reflection Coefficient
At the load (z = 0):
Reflection
coefficient
Normalized load
impedance
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27. Voltage Reflection Coefficient
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