Textbook CHAPTER 7

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Textbook CHAPTER 7
TRANSMISSION LINES
INTRODUCTION
7.1 CHARACTERISTICS OF WAVE PROPAGATAION IN
TRANSMISSION LINES
7.2 DISTRIBUTED CIRCUIT REPRESENTATION OF
TRANSMISSION LINES
From 7.3 to 7.9 (pages 485 to 616 will be studied
later!)
7.10 SINUSOIDAL STEADY-STATE ANALYSIS OF
TRANSMISSION LINES
7.11 REFLECTIONS ON TRANSMISSION LINES WITH
SINUSOIDAL EXCITATIONS
7.12 7.16 TRANSMISSION LINE IMPEDANCES WITH
APPLICATIONS (SMITH CHART, IMPEDANCE
MATCHING, VSWR MEASUREMENTS)
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7.14 IMPEDANCE MATCHING OF LOSSLESS LINES
We feed a load through a transmission line,
and the load impedance is different from the
characteristic impedance of the transmission
line, i.e. REFLECTION occurs at the load.
(E.g. load is far from the power station, or an
antenna is far from the transmitter or receiver)
To (i) protect the generator, or (ii) to
minimize distortion of transmitted signals, or
(iii) Maximize power delivered to load
REFLECTION AT THE LOAD NEED TO BE ELIMINATED, or
at least MINIMIZED
Impedance matching at a single frequency, or in a
frequency band (Broad-band matching)
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IMPEDANCE MATCHING WITH A QUARTER-WAVELENGTH
TRANSFORMER
Transmission line feeding the load
Example 7.12
Dipole antenna at
Quarter wavelength matching
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IMPEDANCE MATCHING
QUARTER-WAVELENGTH TRANSFORMER
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SINGLE-STUB IMPEDANCE MATCHING
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7.15 VOLTAGE STANDING-WAVE RATION (VSWR) ALONG
LOSSLESS TRANSMISSION LINES
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Traveling wave
Standing wave
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Scattering (reflection) The Smith diagram
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The characteristic impedance (wave impedance) of
a lossless transmission line is
Example 1
The load impedance was measured
Determine the impedance at a distance
toward the generator .

Use the Smith Chart!
The normalized value of the load impedance is
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We read the normalized Impedance at B
The total field impedance
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Example 2
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Assignments Textbook Chapters 7.12, , 7.13,
7.14 Study examples 7.9, 7.11, 7.14
Homework 7.20, 7.23, 7.25
Homework deadline 20th March 2008