\documentclass{article}
\usepackage{ifthen}
\usepackage{epsfig}
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\usepackage{newunicodechar}
  \newunicodechar{⁻}{${}^{-}$}% Superscript minus
  \newunicodechar{²}{${}^{2}$}% Superscript two
  \newunicodechar{³}{${}^{3}$}% Superscript three

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\begin{document}
$ y=\sqrt E_s \exp(j \phi) +n = (\sqrt E_s \cos(\phi)+n_1)+j(\sqrt E_s \sin(\phi)+n_2) $
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$n_1$
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$n_2$
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$\sigma^2$
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$ A=E^2(\sqrt E_s \cos(\phi)+n_1)= E_s \cos^2(\phi) $
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$ B = E[ ( \sqrt E_s \cos(\phi)+n_1)^2] = E_s \cos^2(\phi)+\sigma^2 $
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$ B^2-A = \sigma^2 $
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$2^m$
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$ N_0 $
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$m$
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\end{document}
