new Lossless Transmission Line 2_2.ppt

8/14/2019 new Lossless Transmission Line 2_2.ppt

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Lossless Transmission Line

If

Then: All TEM, LC=

Selected conductors: High conductivitiesDielectric materials: negligible conductivities


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Voltage Reflection Coefficient

At the load ( z = 0):

Reflectioncoefficient

Normalized loadimpedance

(2.55)


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Voltage Reflection Coefficient


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Current Reflection Coefficient


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Standing Waves

voltage magnitude

current


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Standing Wave Patterns for 3 Types ofLoads

0

1

1


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Maxima & Minima (cont.)

S = Voltage Standing Wave Ratio

For a matched load: S = 1

For a short, open, or purely reactive load:


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Example 2-6: Measuring Z L with a Slotted Line


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Wave Impedance

At a distance d from the load:


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Input Impedance

At input, d = l :


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(cont.)

Cont.


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(cont.)


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Short-Circuited Line

For the short-circuited line:

At its input, the line appearslike an inductor or a capacitordepending on the sign of


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Open-Circuited Line


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Short-Circuit/Open-CircuitMethod

For a line of known length l , measurements of its inputimpedance, one when terminated in a short circuit and anotherwhen terminated in an open circuit, can be used to find itscharacteristic impedance Z 0 and electrical length


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Instantaneous Power Flow


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Average Power

new Lossless Transmission Line 2_2.ppt

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