1. Parseval定理
帕塞瓦尔定理(Parseval’s theorem)表明了信号在时域和频域上的能量相等,即

式中,
是信号
的Fourier变换,
.
2. 证明
![\int_{-\infty}^{\infty}|f(t)|^2dt \\ = \int_{-\infty}^{\infty}f(t)f^*(t)dt \\ = \int_{-\infty}^{\infty}\left [ \frac{1}{2\pi}\int_{-\infty}^{\infty}F(\omega)e^{j\omega t}d\omega \right ] \left [ \frac{1}{2\pi}\int_{-\infty}^{\infty}F^*(\omega')e^{-j\omega' t}d\omega' \right ]dt\\ = \frac{1}{2\pi}\int_{-\infty}^{\infty}F(\omega)\frac{1}{2\pi}\int_{-\infty}^{\infty}F^*(\omega')\left [ \int_{-\infty}^{\infty}e^{j[\omega-\omega']t}dt \right ]d\omega' d\omega\\ = \frac{1}{2\pi}\int_{-\infty}^{\infty}F(\omega)\frac{1}{2\pi}\int_{-\infty}^{\infty}F^*(\omega')2\pi\delta(\omega - \omega')d\omega' d\omega\\ = \frac{1}{2\pi}\int_{-\infty}^{\infty}F(\omega)F^*(\omega)d\omega\\ = \frac{1}{2\pi}\int_{-\infty}^{\infty}|F(\omega)|^2d\omega](https://javaforall.net/wp-content/uploads/2020/11/2020110817443450.jpg)
得证。
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帕塞瓦尔定理(Parseval‘s theorem)的证明帕塞瓦尔定理 Parseval stheorem 表明了信号在时域和频域上的能量相等
帕塞瓦尔定理(Parseval’s theorem)表明了信号在时域和频域上的能量相等,即

式中,
是信号
的Fourier变换,
.
![\int_{-\infty}^{\infty}|f(t)|^2dt \\ = \int_{-\infty}^{\infty}f(t)f^*(t)dt \\ = \int_{-\infty}^{\infty}\left [ \frac{1}{2\pi}\int_{-\infty}^{\infty}F(\omega)e^{j\omega t}d\omega \right ] \left [ \frac{1}{2\pi}\int_{-\infty}^{\infty}F^*(\omega')e^{-j\omega' t}d\omega' \right ]dt\\ = \frac{1}{2\pi}\int_{-\infty}^{\infty}F(\omega)\frac{1}{2\pi}\int_{-\infty}^{\infty}F^*(\omega')\left [ \int_{-\infty}^{\infty}e^{j[\omega-\omega']t}dt \right ]d\omega' d\omega\\ = \frac{1}{2\pi}\int_{-\infty}^{\infty}F(\omega)\frac{1}{2\pi}\int_{-\infty}^{\infty}F^*(\omega')2\pi\delta(\omega - \omega')d\omega' d\omega\\ = \frac{1}{2\pi}\int_{-\infty}^{\infty}F(\omega)F^*(\omega)d\omega\\ = \frac{1}{2\pi}\int_{-\infty}^{\infty}|F(\omega)|^2d\omega](https://javaforall.net/wp-content/uploads/2020/11/2020110817443450.jpg)
得证。
发布者:全栈程序员-站长,转载请注明出处:https://javaforall.net/176068.html原文链接:https://javaforall.net