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Complex Propogation Constant |
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The propagation constant  in general is complex |
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The wave amplitude varies as  . That is  denotes the exponential decay of the wave along its
direction of propagation. therefore is called the 'Attenuation Constant' of the line . It has the unit Neper/m .
For =1 Neper/m, the wave amplitude reduces to 1/e of its initial value over a distance of 1m. |
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Many times the attenuation of a wave is measured in terms of dB/m. therefore can be given in dB/m, where |
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Note |
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In voltage/current expressions,  should always be in Neper/m. Therefore if  is given in dB/m it should be
converted to Neper/m before it is used in the voltage/current equations. |
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The wave phase has two components |
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Time phase  |
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Space phase  |
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The parameter  gives the phase change per unit length and hence called the 'Phase Constant' of the line.
Its units are Radian/m. |
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Now for a wave the distance over which the phase changes by  is called the ' wavelength '  .
Therefore the phase change per unit length |
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