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So, the normalized power for unipolar NRZ scheme is $\frac{1}{2}V^2$. According to my book, the normalized power required for polar NRZ is half that of unipolar NRZ. So, the power should be $\frac{V^2}{4}$.

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However, the normalized power for polar NRZ seems to me to be $\frac{1}{2}V^2+\frac{1}{2}(-V)^2=V^2$. Can someone please explain this contradiction?

Diagrams from Data Communications and Networking, Behrouz A. Forouzan, p. 101-2

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If the levels of the polar signal were $\pm V$ you would be right, but then it wouldn't be a fair comparison with the unipolar signal with levels $+V$ and zero. A fair comparison would be to have the same difference between the two levels. So we look at a polar signal with levels $\pm V/2$, which has a power of $V^2/4$.

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  • $\begingroup$ ok so if for unipolar nrz the levels are 5V and 0V, then for polar nrz we have to use +2.5V and -2.5V? $\endgroup$ Nov 20, 2023 at 6:47
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    $\begingroup$ @tryingtobeastoic: Yes, for the comparison to be fair. $\endgroup$
    – Matt L.
    Nov 20, 2023 at 7:06

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