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< link rel ="dns-prefetch " href ="http://yoursite.com ">
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< title > DTFT | Hexo</ title >
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< meta name ="viewport " content ="width=device-width, initial-scale=1, maximum-scale=1 ">
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- < meta name ="description " content ="DTFT \begin{aligned} X(f) &= \int_{-\infty}^{\infty} x(t) e^{-j2\pi ft} dt\\ x^*(t) &= \int_{-\infty}^{\infty} X(f) e^{j2\pi ft} df\\ \end{aligned}When $\hat{x}(t) = x(t) p(t) = x(t) \cdot \sum \delta ">
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+ < meta name ="description " content ="DTFT \begin{aligned} X(f) &= \int_{-\infty}^{\infty} x(t) e^{-j2\pi ft} dt\\ x^*(t) &= \int_{-\infty}^{\infty} X(f) e^{j2\pi ft} df\\ \end{aligned} ">
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< meta property ="og:type " content ="article ">
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< meta property ="og:title " content ="DTFT ">
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< meta property ="og:url " content ="http://yoursite.com/2020/05/12/DTFT/index.html ">
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< meta property ="og:site_name " content ="Hexo ">
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- < meta property ="og:description " content ="DTFT \begin{aligned} X(f) &= \int_{-\infty}^{\infty} x(t) e^{-j2\pi ft} dt\\ x^*(t) &= \int_{-\infty}^{\infty} X(f) e^{j2\pi ft} df\\ \end{aligned}When $\hat{x}(t) = x(t) p(t) = x(t) \cdot \sum \delta ">
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+ < meta property ="og:description " content ="DTFT \begin{aligned} X(f) &= \int_{-\infty}^{\infty} x(t) e^{-j2\pi ft} dt\\ x^*(t) &= \int_{-\infty}^{\infty} X(f) e^{j2\pi ft} df\\ \end{aligned} ">
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< meta property ="og:locale " content ="en_US ">
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- < meta property ="article:published_time " content ="2020-05-12T23:16:42.809Z ">
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- < meta property ="article:modified_time " content ="2020-02-23T22:43:31.872Z ">
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+ < meta property ="article:published_time " content ="2020-05-13T03:56:48.428Z ">
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+ < meta property ="article:modified_time " content ="2020-05-13T03:56:48.428Z ">
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< meta property ="article:author " content ="dassein ">
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+ < meta property ="article:tag " content ="DSP ">
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+ < meta property ="article:tag " content ="math ">
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< meta name ="twitter:card " content ="summary ">
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< link rel ="alternative " href ="/atom.xml " title ="Hexo " type ="application/atom+xml ">
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< li > < a href ="/archives/index.html "> 归档</ a > </ li >
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+ < li > < a href ="/categories/index.html "> 分类</ a > </ li >
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< nav class ="header-smart-menu ">
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< nav class ="header-nav ">
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</ nav >
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< nav class ="header-menu js-header-menu ">
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- < li style ="width: 50% "> < a href ="/ "> 主页</ a > </ li >
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+ < li style ="width: 25% "> < a href ="/ "> 主页</ a > </ li >
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+ < li style ="width: 25% "> < a href ="/archives/index.html "> 归档</ a > </ li >
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+ < li style ="width: 25% "> < a href ="/categories/index.html "> 分类</ a > </ li >
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+ < li style ="width: 25 % "> < a href ="/tags /index.html "> 标签 </ a > </ li >
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</ ul >
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</ nav >
@@ -163,7 +177,7 @@ <h1 class="article-title" itemprop="name">
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< a href ="/2020/05/12/DTFT/ " class ="archive-article-date ">
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- < time datetime ="2020-05-12T23:16:42.809Z " itemprop ="datePublished "> < i class ="icon-calendar icon "> </ i > 2020-05-12</ time >
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+ < time datetime ="2020-05-13T03:56:48.428Z " itemprop ="datePublished "> < i class ="icon-calendar icon "> </ i > 2020-05-12</ time >
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</ a >
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</ header >
@@ -174,7 +188,8 @@ <h2 id="DTFT"><a href="#DTFT" class="headerlink" title="DTFT"></a>DTFT</h2><scri
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\begin { aligned }
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X ( f ) & = \int_ { - \infty } ^ { \infty } x ( t ) e ^ { - j2 \pi ft } dt \\
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x ^ * ( t ) &= \int_ { - \infty } ^ { \infty } X ( f ) e ^ { j2 \pi ft} df \\
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- \end { aligned} </ script > < p > When $\hat{x}(t) = x(t) p(t) = x(t) \cdot \sum \delta(t-nT)= \sum x(nT) \delta(t-nT)$, then we have $\lambda < 1$ that</ p >
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+ \end { aligned} </ script > < a id ="more "> </ a >
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+ < p > When $\hat{x}(t) = x(t) p(t) = x(t) \cdot \sum \delta(t-nT)= \sum x(nT) \delta(t-nT)$, then we have $\lambda < 1$ that</ p >
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< script type ="math/tex; mode=display ">
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\begin { aligned }
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\hat { X } ( f ) &= \int_ { - \infty } ^ { \infty } \hat { x } ( t ) e ^ { - j2 \pi ft } dt = \sum_n x ( nT ) \int_ { - \infty } ^ { \infty } \delta ( t - nT ) e ^ { - j2 \pi ft } dt \\
@@ -227,7 +242,7 @@ <h2 id="DTFT"><a href="#DTFT" class="headerlink" title="DTFT"></a>DTFT</h2><scri
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&= \sum_n x ( nT ) e ^ { - j2 \pi n ( f / f_s ) } \\
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\hat { x } ^ * ( t ) &= \int_ { - \infty } ^ { \infty } \hat { X } ( f ) e ^ { j2 \pi ft} df \\
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x ( nT ) & = \int_ { - \infty } ^ { \infty } \hat { x } ^ * ( t ) \frac { \sin ( \pi ( t - nT ) ) } { \pi ( t - nT ) } dt \\
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- &= \int_ { - 0.5 } ^ { 0.5 } \hat { X } ( f ) e ^ { j2 \pi ( f / f_s ) n } d ( f / f_s ) \\
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+ &= \int_ { - 0.5 } ^ { 0.5 } \hat { X } ( f ) e ^ { j2 \pi ( f / f_s ) n } d ( f / f_s ) \\
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\end { aligned } </ script > < p > Now define $\omega = 2\pi f/f_s$, then</ p >
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< script type ="math/tex; mode=display ">
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X ( e ^ { jw} ) \equiv \hat { X } ( f ) = \sum_n x ( nT ) [ e ^ { j \omega} ] ^ { - n} \\
@@ -290,14 +305,14 @@ <h2 id="DTFT"><a href="#DTFT" class="headerlink" title="DTFT"></a>DTFT</h2><scri
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&= \sum_ { k} \Bigg [ \frac { f_s} { N} \left \{ \sum_ { n= 0 } ^ { N - 1 } x ( nT ) e ^ { - j2 \pi ( k / N ) n } \right \} \Bigg ] \int_ { - \infty } ^ { \infty } e ^ { j2 \pi ft} \delta ( f - k \frac { f_s} { N} ) df \\
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&= \sum_ { k} \Bigg [ \frac { f_s} { N} \left \{ \sum_ { n= 0 } ^ { N - 1 } x ( nT ) e ^ { - j2 \pi ( k / N ) n } \right \} \Bigg ] e ^ { j2 \pi ( k / N ) f_st } \\
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x ( nT ) & = \int_ { - \infty } ^ { \infty} \tilde { x } ^ * ( t ) \frac { \sin ( \pi ( t - nT ) ) } { \pi ( t - nT ) } dt \\
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- &= \int_ { - 0.5 } ^ { 0.5 } \tilde { X} ( f ) e ^ { j2 \pi ( f / f_s ) n } d ( f / f_s ) = \int_ { 0 } ^ { 1 } \tilde { X} ( f ) e ^ { j2 \pi ( f / f_s ) n } d ( f / f_s ) \\
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+ &= \int_ { - 0.5 } ^ { 0.5 } \tilde { X} ( f ) e ^ { j2 \pi ( f / f_s ) n } d ( f / f_s ) = \int_ { 0 } ^ { 1 } \tilde { X} ( f ) e ^ { j2 \pi ( f / f_s ) n } d ( f / f_s ) \\
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&= \int_ { 0 } ^ { 1 } e ^ { j2 \pi ( f / f_s ) n } d ( f / f_s ) \sum_ { k} \delta ( f - k \frac { f_s} { N} ) \Bigg [ \frac { f_s} { N} \left \{ \sum_ { n= 0 } ^ { N - 1 } x ( nT ) e ^ { - j2 \pi ( k / N ) n } \right \} \Bigg ] \\
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- &= \sum_ { k} \int_ { 0 } ^ { 1 } e ^ { j2 \pi ( \frac { f} { f_s} ) n} \delta ( \frac { f} { f_s} - \frac { k} { N} ) d ( \frac { f} { f_s} )
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+ &= \sum_ { k} \int_ { 0 } ^ { 1 } e ^ { j2 \pi ( \frac { f} { f_s} ) n} \delta ( \frac { f} { f_s} - \frac { k} { N} ) d ( \frac { f} { f_s} )
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\Bigg [ \frac { 1 } { N} \left \{ \sum_ { n= 0 } ^ { N- 1 } x ( nT ) e ^ { - j2 \pi ( k / N ) n} \right \} \Bigg ] \\
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- &= \sum_ { k} \int_ { 0 } ^ { 1 } e ^ { j2 \pi ( \frac { k} { N} ) n} \delta ( \frac { f} { f_s} - \frac { k} { N} ) d ( \frac { f} { f_s} )
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- \Bigg [ \frac { 1 } { N} \left \{ \sum_ { n= 0 } ^ { N- 1 } x ( nT ) e ^ { - j2 \pi ( k / N ) n} \right \} \Bigg ] \\
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- &= \sum_ { k= 0 } ^ { N- 1 } e ^ { j2 \pi ( \frac { k} { N} ) n} \Bigg [ \frac { 1 } { N} \left \{ \sum_ { n= 0 } ^ { N- 1 } x ( nT ) e ^ { - j2 \pi ( k / N ) n} \right \} \Bigg ] \\
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- &= \frac { 1 } { N} \sum_ { k= 0 } ^ { N- 1 } \left \{ \sum_ { n= 0 } ^ { N- 1 } x ( nT ) e ^ { - j2 \pi ( \frac { k} { N} ) n} \right \} e ^ { j2 \pi ( \frac { k} { N} ) n}
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+ &= \sum_ { k} \int_ { 0 } ^ { 1 } e ^ { j2 \pi ( \frac { k} { N} ) n} \delta ( \frac { f} { f_s} - \frac { k} { N} ) d ( \frac { f} { f_s} )
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+ \Bigg [ \frac { 1 } { N} \left \{ \sum_ { n= 0 } ^ { N- 1 } x ( nT ) e ^ { - j2 \pi ( k / N ) n} \right \} \Bigg ] \\
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+ &= \sum_ { k= 0 } ^ { N- 1 } e ^ { j2 \pi ( \frac { k} { N} ) n} \Bigg [ \frac { 1 } { N} \left \{ \sum_ { n= 0 } ^ { N- 1 } x ( nT ) e ^ { - j2 \pi ( k / N ) n} \right \} \Bigg ] \\
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+ &= \frac { 1 } { N} \sum_ { k= 0 } ^ { N- 1 } \left \{ \sum_ { n= 0 } ^ { N- 1 } x ( nT ) e ^ { - j2 \pi ( \frac { k} { N} ) n} \right \} e ^ { j2 \pi ( \frac { k} { N} ) n}
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\end { aligned} </ script >
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@@ -327,7 +342,33 @@ <h2 id="DTFT"><a href="#DTFT" class="headerlink" title="DTFT"></a>DTFT</h2><scri
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< div class ="article-info article-info-index ">
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+ < a href ="javascript:void(0) " class ="js-tag article-tag-list-link color4 "> DSP</ a >
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+ </ li >
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+ < a href ="javascript:void(0) " class ="js-tag article-tag-list-link color5 "> math</ a >
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+ < li class ="article-tag-list-item ">
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+ < a href ="/categories/信号处理// " class ="article-tag-list-link color5 "> 信号处理</ a >
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+ </ li >
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+ </ div >
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@@ -401,11 +442,6 @@ <h2 id="DTFT"><a href="#DTFT" class="headerlink" title="DTFT"></a>DTFT</h2><scri
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</ a >
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@@ -560,6 +596,22 @@ <h2 id="DTFT"><a href="#DTFT" class="headerlink" title="DTFT"></a>DTFT</h2><scri
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+ < a href ="javascript:void(0) " class ="js-tag color5 "> Hexo</ a >
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+ < a href ="javascript:void(0) " class ="js-tag color3 "> MathJax</ a >
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