Why must X(s) occur in conjugate reciprocal pairs for a real x(t)?

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SUMMARY

The discussion centers on the necessity of conjugate reciprocal pairs for the Laplace transform X(s) of a real time function x(t). It establishes that while x(t) can be real, such as in the case of x(t) = e^{at}, leading to a real pole at s = a, sinusoidal functions result in complex conjugate poles in X(s). This distinction highlights the conditions under which poles appear in the Laplace domain based on the nature of the time-domain function.

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khdani
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Hello,
if i said that x(t) is real,
why X(s) must occur in conjugate reciprocal pairs ?
 
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It does not.
If [tex]x(t) = e^{at}[/tex], then [tex]X(s) = \frac{1}{s-a}[/tex], which has a real pole at s = a.
In the other way, if x(t) is a sinusoid, then X(s) will have complex conjugate poles.
 

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